Atle Mysterud

• Lettenmaier, Ludwig; Eisenhauer, Nico; Cesarz, Simone; Ammer, Christian; Bucharova, Anna & Dittrich, Sebastian [Vis alle 16 forfattere av denne artikkelen] (2026). Native earthworms and roe deer in temperate forests: Friends in the sun, foes in the shade. Ecology. ISSN 0012-9658. 107(9). doi: 10.1002/ecy.70520. Fulltekst i vitenarkiv
• Lettenmaier, Ludwig; Cadotte, Marc W.; Dittrich, Sebastian; Pierick, Kerstin; Ammer, Christian & Bradler, Pia M. [Vis alle 15 forfattere av denne artikkelen] (2026). Contrasting direct and indirect effects of roe deer on herb layer vegetation in gaps and closed canopies. Journal of Ecology. ISSN 0022-0477. 114(6). doi: 10.1111/1365-2745.70382.
• Cerca, José; Ravinet, Mark; Flagstad, Øystein; Rolandsen, Christer Moe; Strand, Olav & Tørresen, Ole Kristian [Vis alle 8 forfattere av denne artikkelen] (2026). Hybridization with wild individuals fuels reindeer feralization. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 293(2075), s. 1–11. doi: 10.1098/rspb.2026.1226. Fulltekst i vitenarkiv Vis sammendrag

  Domestication has profoundly influenced the development of human agriculture, and is characterized by intense artificial selection. Feralization occurs when domestic animals return to the wild. Although feralization does not fully reverse domestication traits, the selective pressures and evolutionary mechanisms driving it remain poorly understood. In northern Europe and Asia, wild, semi-domesticated and feral reindeer (Rangifer tarandus) populations coexist, offering a unique opportunity to study feralization. We studied genomic signatures of selection in semi-domesticated, feral and wild reindeer populations in Norway. Analysis of population structure confirmed historical records indicating the feral population formed a monophyletic clade that originated from neighbouring semi-domesticated reindeer. However, we also found evidence for excess allele-sharing between wild and feral reindeer, indicating hybridization between these lineages. Signatures of selection were identified using a top-down approach (orthologues of domestication candidate genes) and a bottom-up approach (FST and extended haplotypes). We found that candidate regions under selection have higher rates of excess allele-sharing between wild and feral populations. This provides the first evidence of reversed selection pressures during feralization in reindeer and reveals a link between selection and hybridization. Together, our findings suggest that hybridization likely promoted adaptive introgression during feralization. We discuss the implications of our findings for conserving the genetic integrity of endangered wild reindeer populations.

• Oeser, Julian; Kowalczyk, Rafał; Kuijper, Dries; Neumann, Wiebke; Reiner, Rudolf & Seidl, Rupert [Vis alle 65 forfattere av denne artikkelen] (2026). Increasing forest disturbance enhances habitat suitability for Europe’s large herbivores. Nature Ecology and Evolution. 10, s. 1273–1286. doi: 10.1038/s41559-026-03096-0. Fulltekst i vitenarkiv Vis sammendrag

  Forest disturbances have increased in many regions, but how they impact habitat suitability for wildlife remains poorly understood. Here, by combining tracking data on 3,069 individuals of four ungulate species (European bison, moose, red deer and roe deer) with satellite-based maps, we perform a continental, multi-decadal assessment of large herbivore responses to forest disturbance. Despite strong intraspecific variation, all species show an increased selection of disturbed areas for ≥35 years after disturbance. Although the patterns closely reflect species-specific foraging strategies, all species selected more strongly for smaller disturbance patches, depending on the availability of alternative foraging habitats (grasslands and croplands). Model projections across the species’ range extents show positive but regionally varying effects of forest disturbances on habitat suitability between 2000 and 2023. Our findings indicate that forest disturbances can attract large herbivores and that the recent increase in forest disturbances improved habitat suitability for our study species across Europe, highlighting the importance of considering long-term disturbance-related dynamics for wildlife and forest management. Given expected future increases in disturbance, resulting habitat improvements could amplify conflicts with forestry, but also contribute to restoring large herbivores and their ecological functions.

• Potts, Jonathan R.; Börger, Luca; Tucker, Marlee A.; Ossi, Federico; Yanco, Scott W. & Ellis‐Soto, Diego [Vis alle 76 forfattere av denne artikkelen] (2026). Understanding mammal avoidance of human settlements. Journal of Animal Ecology. ISSN 0021-8790. doi: 10.1111/1365-2656.70298. Fulltekst i vitenarkiv Vis sammendrag

  Anthropogenic land conversion is putting increasing pressure on wildlife populations around the world. To mitigate impacts, it is necessary to develop a detailed mechanistic understanding of how animals are affected by different types of human activity. A key challenge is to disentangle the effects of static infrastructure, like roads or buildings, and the presence of humans in the landscape. To address this question, we examined if terrestrial mammals altered their movement behaviour around buildings in response to reduced human mobility during COVID‐19 lockdowns. We compiled GPS tracking data from 35 study sites across five continents, for 10 carnivore species and 13 herbivore species, totalling >1 million location records from 586 individuals. For each study, we used integrated step selection analysis to test the extent to which animals changed their avoidance of buildings as lockdown took effect, leveraging the recently released Microsoft MLBuildings dataset of global building locations. Analysis of population‐level effects revealed that, in areas with high Human Footprint Index (HFI), animals tended to show a significant reduction in their avoidance of buildings during lockdown, but not in low HFI areas. No such trend was detected during equivalent periods in years other than 2020, indicating that behavioural changes were a result of reduced human mobility during lockdowns. Overall, our findings suggest that animals living alongside humans exhibit greater plasticity when people change their behaviour, likely indicating the combined effects of environmental filtering and habituation. More generally, our study provides a critical first step towards developing evidence‐based tools for forecasting how wildlife movement behaviour may change in response to different land‐use strategies, human activities, conservation interventions or environmental perturbations.

• Cerri, Jacopo; Chirichella, Roberta; Arnold, Walter; Bartoš, Luděk; Borowik, Tomasz & Carranza, Juan [Vis alle 33 forfattere av denne artikkelen] (2026). Trends of ungulate species in Europe: not all stories are equal. Mammal Research. ISSN 2199-2401. 71(2). doi: 10.1007/s13364-025-00838-6. Fulltekst i vitenarkiv
• Unsgård, Even; Mysterud, Atle; Rivrud, Inger Maren; Hylen, Gro; Øpstad, Samson & Meisingset, Erling (2026). Risk factors for bark stripping damage on Norway spruce by red deer. Wildlife Biology. ISSN 0909-6396. 2026(3). doi: 10.1002/wlb3.01613. Fulltekst i vitenarkiv Vis sammendrag

  Norway spruce Picea abies is an economically important tree species in Europe, actively managed for forestry. Among the most negative biotic factors for growth and hence forest production is damage caused by wildlife, such as damage through bark stripping by red deer Cervus elaphus. We quantified bark stripping damage on Norway spruce trees in across 450 stands (aged 20–72 years) spanning a 400 km latitudinal range along Norway's west coast and analysed the underlying mechanisms driving increased probability of bark stripping by red deer. A total of 74% of tree stands had bark stripping damage. The mean percentage of damaged trees was 16.0%, but 50 stands (11.1% of the stands) had more than 50.0% damaged trees. The most important factor determining probability for bark stripping was broad-scale red deer density, where the probability increased markedly when density reached approximately two harvested red deer per km2. In addition, proximity to agricultural farmland, distance from roads, site productivity, distance between twig whorls and terrain ruggedness index increased the probability of bark stripping. Our study on bark stripping on Norway spruce highlights the importance of red deer population control, but also the importance of evaluating environmental factors as well as site factors and tree characteristics in forestry planning to mitigate damage from red deer.

• Bommerlund, Julie; Ergon, Torbjørn Håkan; Filhol, Simon & Mysterud, Atle (2026). Estimating red deer Cervus elaphus population density using drones in a steep and rugged terrain. Wildlife Biology. ISSN 0909-6396. doi: 10.1002/wlb3.01533. Fulltekst i vitenarkiv Vis sammendrag

  Precise and accurate information about population density, crucial for wildlife management, is difficult to obtain for elusive species living in dense forests or steep and inaccessible terrain. Using unmanned aerial vehicles (UAVs), we developed a method for obtaining absolute population estimates of ungulates living in steep, rugged, and partly forested terrain. The UAVs were used to collect data from four different case study areas in two consecutive months in winter/early spring (before leaf growth) in Lærdal, Norway. The detections of red deer Cervus elaphus from UAV images were done using a double observer protocol, and hierarchal state–space models were fitted to the data using a Bayesian framework to obtain posterior distributions of absolute deer density. Results indicate that availability bias was negligible when deer can be searched for in multiple UAV images of the sites (sample plots) taken from different angles by a UAV at 60 m above ground level but detection probability in the images was significantly below one and must hence be accounted for. Although the credible intervals were rather wide, our results demonstrate that absolute red deer density estimates with quantifiable uncertainties can be produced using this method. Lower credible limits for the estimates indicate that densities in two of the study areas were consistently well above management target densities during the two consecutive months. The high spatial variation in deer densities (at various scales) in our study pose a major challenge, as large areas with a high number of sampling sites must be covered to model the spatial variation and obtain reliable and precise density estimates at a scale relevant for management. We nevertheless conclude that the method has potential for reliable spatiotemporal deer density estimation, given sufficient resources and field efforts.

• Franke, Björn H.; Schipper, Aafke M.; Avgar, Tal; Börger, Luca; Chatterjee, Nilanjan & Müller, Thomas [Vis alle 78 forfattere av denne artikkelen] (2026). Local and Landscape‐Level Environmental Conditions Drive Habitat Selection Across Terrestrial Mammal Species. Global Ecology and Biogeography. ISSN 1466-822X. 35(3). doi: 10.1111/geb.70212. Fulltekst i vitenarkiv Vis sammendrag

  Aim Animal movements are a fundamental process affecting communities and ecosystems. Quantifying habitat selection across species and habitats is key for understanding how animals respond to environmental change. Currently, we lack comparative studies that examine how habitat selection varies across species traits and landscapes. We aim to quantify global patterns of habitat selection to help understand the fundamental drivers of movement behaviour. Location: Global. Time Period: Contemporary. Major Taxa Studied: Terrestrial mammals. Methods We estimated selection coefficients for terrain ruggedness, vegetation productivity, human population density and distance to roads of individual terrestrial mammals through step‐selection analysis of 1344 GPS tracks across 48 species. We quantified intra‐ and interspecific variation and tested whether selection coefficients were associated with species traits and habitat availability. Results We observe an overall avoidance of roads and areas of high human population density as well as rugged terrain, with a large proportion of individuals selecting for areas of intermediate NDVI. However, we also found large intraspecific variation in habitat selection and show that this variation is predicted by local and landscape‐level environmental conditions rather than species traits. Individuals in more remote areas exhibited weaker functional responses to human presence than those in more disturbed areas. Avoidance of rugged terrain is also context‐dependent, with stronger avoidance when local ruggedness is high. The only exception to the observed intraspecific variability is consistent species‐level responses to road proximity. Main Conclusions Our findings contribute to the understanding of habitat selection by terrestrial mammals, showing that selection is largely shaped by environmental conditions and that animals exhibit high plasticity in their responses. Our results also provide further evidence for the significant impact of roads on animal movement. These insights can help us to understand the potential effects of environmental change on the behaviour of mammal species around the world.

• Tørresen, Ole K; Tooming-Klunderud, Ave; Skage, Morten; Streitlien, Anne Eline; Strand, Olav & Rolandsen, Christer Moe [Vis alle 10 forfattere av denne artikkelen] (2025). Chromosome-level genome assembly of Norwegian wild alpine reindeer (Rangifer tarandus tarandus). Journal of Heredity. ISSN 0022-1503. doi: 10.1093/jhered/esaf094. Fulltekst i vitenarkiv Vis sammendrag

  We describe a chromosome-level genome assembly from a wild alpine reindeer individual (Rangifer tarandus tarandus) from the Rondane area in Southern Norway. The assembly is resolved into two pseudo-haplotypes: hap 1 spanning 3,081 Mb and hap 2 spanning 2,633 Mb. Contig N50 and scaffold N50 lengths are in the range of 31 to 41 and 66 to 69 Mb, respectively. A large part of these two haplotypes (83.8% and 90.4%, respectively) are scaffolded into 34 autosomal chromosomal pseudomolecules, and in sex chromosomes X and Y for hap 1. The BUSCO completeness scores are 98.0% and 95.2%, respectively, and gene annotations of the assemblies identified 37,998 and 36,977 protein-coding genes. We also present an updated and improved genome assembly for Svalbard reindeer (Rangifer tarandus platyrhynchus; contig N50 46 to 48 Mb, scaffold N50 67 to 71 Mb, BUSCO 95.4% to 98.0%) and a comparison with previously published genome assemblies of reindeer.

• Lettenmaier, Ludwig; Mysterud, Atle; Mitesser, Oliver; Ammer, Christian; Hothorn, Torsten & Cesarz, Simone [Vis alle 11 forfattere av denne artikkelen] (2025). Light and ungulate browsing interact in shaping future woody plant diversity through natural regeneration. Journal of Applied Ecology. ISSN 0021-8901. 62(12), s. 3367–3380. doi: 10.1111/1365-2664.70211. Fulltekst i vitenarkiv Vis sammendrag

  1. Woody species diversity is crucial for the resilience of forests under climate change. The early stages of regeneration, particularly after canopy disturbance, shape the composition of future forest. Light availability, browsing pressure and their interactions should be key drivers of woody species diversity, biomass and density, but are not well understood due to limited experimental setups. 2. We used exclosures in a mixed broadleaf forest with high woody diversity to protect seedlings from browsing by roe deer (Capreolus capreolus), the predominant ungulate in Central Europe. In a full-factorial design, we paired 75 exclosure (fenced) and control (unfenced) plots in both closed canopy stands and experimental gaps. We measured woody regeneration 1 and 4 years after the start of the treatments. 3. Rarefaction-extrapolation curves revealed that diversity of common (Shannon diversity) woody species was highest in sunny and shaded exclosures (7), compared to sunny (4.5) and shaded (3.5) controls, for species that had outgrown the 130 cm browsing-susceptible height of roe deer. 4. Stage-structured matrix models showed that saplings ≤20 cm had the highest probability of reaching >130 cm within 3 years in sunny exclosures (1.51%), followed by sunny controls (0.32%), shaded exclosures (0.27%) and shaded controls (0.07%). 5. Browsing resulted in homogenized woody regeneration, particularly in forest gaps. Increasing light availability did not compensate for diversity loss by browsing. Given the densities of roe deer in the study area—typical for many Central European forests—effective population control or fencing appears essential to maintain high diversity of future forest shaping and forestry relevant woody species, especially in open forests. 6. Synthesis and applications. Our results provide strong evidence that in the current context of increasing tree mortality and subsequent light availability, roe deer act as a keystone species. It is crucial to implement browsing protection measures and control roe deer population before or immediately after canopy disturbance. Otherwise, the rapid growth of a few dominant, browsing-resistant woody species will significantly reduce the woody plant diversity of future forests.

• Velling, Marc; Peters, Anne; Ferry, Nicolas; Bechert, Ursula; Schwarzenberger, Franz & Göritz, Frank [Vis alle 9 forfattere av denne artikkelen] (2025). One-time administration of the SpayVac ® vaccine prevents pregnancy in red deer (Cervus elaphus) in a temperate forest ecosystem. European Journal of Wildlife Research. ISSN 1612-4642. 71(5). doi: 10.1007/s10344-025-01988-3. Fulltekst i vitenarkiv Vis sammendrag

  Contraception has traditionally been used on domesticated and captive animals, but it has also found increasing application in locally overabundant wildlife species. Different immunocontraceptives are available and they vary in their mechanisms, effectiveness, and potential side-effects. In this study, the porcine zona pellucida (pZP)-based vaccine SpayVac® was administered to red deer (Cervus elaphus) in the Bavarian Forest National Park and its contraceptive effectiveness was assessed for one year under field conditions. Twenty red deer were vaccinated with a single intramuscular injection, with 27 additional animals serving as controls. All 47 deer were fitted with GPS collars. Reproduction was tracked by observing calves using camera trap surveys and by measuring the concentrations of fecal progesterone metabolites to determine pregnancy. SpayVac® reduced fertility to 11% in vaccinated deer compared to a fertility rate of 86% in control animals for one year. Camera traps and/or progesterone metabolites aided in evaluating the reproductive status of 85% of the studied female red deer. Specifically, reproductive status was determined in 37 of 46 individuals using camera traps, and pregnancy in 19 of 46 females using progesterone metabolites. In all but one deer, the same results were obtained with the two methods. Our study demonstrates the 1-year efficacy of SpayVac® immunocontraception in red deer. It also describes methods for the improved determination of pregnancy status and calf presence in wildlife, using camera traps and fecal progesterone metabolites. Studies evaluating the long-term contraceptive effectiveness and the effects of fertility control on population structure and behavior are still needed.

• Mysterud, Atle; Rivrud, Inger Maren; Meisingset, Erling L.; Jore, Solveig & Viljugrein, Hildegunn (2025). Deer migration, deer density, tick distribution and incidence of a tick‐borne zoonosis. Journal of Animal Ecology. ISSN 0021-8790. 94(12), s. 2655–2670. doi: 10.1111/1365-2656.70163. Fulltekst i vitenarkiv Vis sammendrag

  1. Our understanding of how migratory wildlife populations affect incidence of in-fectious diseases spilling over into humans is limited. Ticks are expanding theirdistribution towards northern latitudes, causing emergence of tick- borne dis-eases. Deer serve as reproduction hosts for adult ticks, supporting the tick pop -ulations. However, in northern areas, deer populations are partially migratory,and migrants occupy high elevation summer ranges that are unsuitable for ticks.Migration can thus theoretically lead to escape from exposure to ticks and to deerfeeding fewer ticks, which lower disease hazard to humans. 2. Combining data on Ixodes ricinus tick abundance with GPS-tracking data of reddeer (Cervus elaphus), we quantified the distributional overlap of ticks and reddeer along elevational gradients in Norway. Furthermore, we correlated bothdeer density and the proportion of migratory deer with the incidence of Lymedisease in humans. 3. We found that migratory deer summer ranges had colder climate and overlappedless with tick distribution than those of resident deer. Deer density consistentlyincreased Lyme disease incidence in humans. However, we found only weak evi-dence that deer migration negatively affected Lyme disease incidence. 4. Our study provides a rare quantification of how host availability, in terms of bothhost density and migratory movement, affects risk of a zoonotic disease.

• Lindsø, Lars; Rivrud, Inger Maren; König, Emilie A.; Herland, Anders & Mysterud, Atle (2025). Diel Niche of Sympatric Small Mammals Revealed by Year-Round Camera Trapping. Ecology and Evolution. 15(6). doi: https:/onlinelibrary.wiley.com/doi/10.1002/ece3.71590. Fulltekst i vitenarkiv Vis sammendrag

  At northern latitudes, small mammals are of key importance for ecosystem dynamics. Yet, few have monitored the small mammal community to accurately investigate activity of sympatric small mammals at finer temporal resolutions, and consequently their temporal niche partitioning that may provide novel insights into how they interact with their environment and each other. Here, we deployed 12 tunnel-based camera traps to continuously monitor a forest community of small mammals in South-East Norway (2018–2020). We statistically determined the diel period selection (cathemeral, nocturnal, diurnal, crepuscular) in the wood mouse (Apodemus sylvaticus), bank vole (Myodes glareolus), common shrew (Sorex araneus) and pygmy shrew (S. minutus). We analyzed how temperature and snow cover influenced small mammal occurrence in winter and whether camera trap observations correlated with numbers from ordinary trapping in spring and fall. In both winter and summer, wood mice were nocturnal, while common shrews were cathemeral. Diel period selection in bank voles and pygmy shrews varied seasonally, and both were cathemeral in summer and nocturnal in winter. The occurrence of both rodents and shrews developed from a low year in 2018, to an increase in 2019, and to a peak year in 2020, albeit at lower amplitudes for the pygmy shrew. Small mammal occurrence in winter was positively influenced by temperature, but the relationship was dependent on snow cover and was only significant at low snow levels. Camera trap occurrence correlated moderately with spatially and temporally coinciding ordinary trapping indices in spring and fall. Thus, tunnel-based camera traps captured a new level of detail in species synchrony of common small mammals in northern Europe at annual, seasonal, and diel scales, yielding a better understanding of their ecology.

• Figueiredo, Ana Manuel Bastos; Alejandro, Dashti,; G., Maloney, Jenny; Aleksey, Molokin,; S., George, Nadja & C., Köster, Pamela [Vis alle 27 forfattere av denne artikkelen] (2025). Blastocystis in free-ranging wild ruminant species across the Iberian Peninsula. Veterinary research (VR). ISSN 0928-4249. 56. doi: 10.1186/s13567-025-01563-3. Fulltekst i vitenarkiv Vis sammendrag

  The growing wild ungulate populations across Europe represents an increasingly important source for the spread of zoonotic pathogens. Blastocystis is a common intestinal protist observed in humans and animals worldwide. Studies on Blastocystis occurrence and subtype (ST) diversity in free-ranging wild ruminants are lacking globally, and more data are needed to understand the epidemiological scenario in wild European ruminants. We collected 833 faecal samples from free-ranging wild ungulates across Spain (n = 699) and Portugal (n = 134) between 1998 and 2021. Using conventional PCR and next-generation amplicon sequencing, Blastocystis was found in 13.8% (115/833; 95% CI: 11.5–16.3) of the wild ruminants analysed. Its occurrence was significantly higher in Portugal (38.1%, 51/134; 95% CI 29.8–46.8) than in Spain (9.2%, 64/699; 95% CI: 7.1–11.5). Fifteen Blastocystis STs, fourteen previously recognised (ST2, ST5, ST10, ST13, ST14, ST21, ST23–ST26, ST30, and ST42–ST44), and one novel (named ST49), were detected among the surveyed wild ruminant populations. Novel ST49 was described using Oxford Nanopore sequencing to produce full-length reference sequences of the small subunit ribosomal RNA gene. A greater ST diversity was observed in Spanish samples. Mixed infections were found in 58.3% (67/115) of the total Blastocystis-positive samples. Our results have enhanced the knowledge regarding Blastocystis occurrence and ST diversity and host preference present in wild ruminants from the Iberian Peninsula, which will assist in clarifying the relationships between the sylvatic and domestic cycles of this protist and may ultimately provide tools to help manage future public health epidemiological scenarios.

• Mysterud, Atle; Tveraa, Torkild; Hansen, Brage Bremset; Gundersen, Vegard; Tømmervik, Hans & Erlandsson, Rasmus [Vis alle 27 forfattere av denne artikkelen] (2025). A quality standard for conservation of wild reindeer. Wildlife monographs. ISSN 0084-0173. 219(1). doi: 10.1002/wmon.70005. Fulltekst i vitenarkiv Vis sammendrag

  Abstract The ongoing biodiversity crisis requires policy tools to establish baselines and assess biodiversity status. Reindeer and caribou ( Rangifer tarandus ) are iconic ungulates in the Arctic and subarctic, but populations are declining. Although the species is considered vulnerable globally in the International Union for Conservation of Nature [IUCN] Red List, more detailed policy tools at the population level would allow for targeted conservation efforts nationally. We developed an environmental quality standard (or norm) for reindeer populations to evaluate their overall status and put complex variation and change into simple status categories (poor, medium, and good) based on sets of quantitative indicators for 1) population performance, genetic diversity, and health status; 2) available lichen resources; and 3) loss of seasonal habitat and connectivity. We implemented the environmental quality standard for 10 national and 14 smaller wild reindeer areas (populations) in Norway. Except for 1 area with good status, all others ranged from medium ( n  = 11) to poor quality ( n  = 12). More than half of the populations had medium ( n  = 7) or poor ( n  = 6) status for 1 or more population performance indicators, with negative trends in calf body mass and recruitment in several populations. High loss of genetic diversity gave poor status in 4 small and isolated populations, and 2 populations with chronic wasting disease scored poor on health status. The status of lichen resources was medium ( n  = 20) or good ( n  = 3), with 1 exception. However, lichen time series data were not available to evaluate temporal trends to assess overgrazing. Loss of connectivity (poor; n  = 7) was more problematic than loss of seasonal habitat ( n  = 3). The poor availability of high‐quality empirical data, particularly on population performance, has limited the ability to fully assess the conservation status of several small populations. The environmental quality standard provides an important step towards operationalizing management and aiding in securing the long‐term conservation of wild reindeer. We discuss further improvements and the potential usefulness of this approach for other large mammals.

• Hjermann, Tilde; Rivrud, Inger Maren; Meisingset, Erling & Mysterud, Atle (2025). Sex-specific selection of agricultural farmland by a partially migratory ungulate. Journal of Animal Ecology. ISSN 0021-8790. 94(5), s. 884–895. doi: 10.1111/1365-2656.70017. Fulltekst i vitenarkiv Vis sammendrag

  1. Large herbivores at northern latitudes often forage on agricultural farmland. In these populations, the presence of both resident and migrant individuals (termed partial migration) is common, but how migrants and residents differ in their selection of farmland is not well-understood. Higher access to farmland may provide benefits to residents compensating for not following the ‘green wave’ of emerging vegetation such as migrants. According to sexual segregation theory, males and females differ in body-size-related nutritional needs and risk sensitivity associated with farmland. Yet, how the sexes differ in the selection of farmland through an annual cycle remains unclear. 2. We quantified seasonal variation in the selection of farmland by partially migratory red deer (Cervus elaphus) at broad, landscape scale and at fine, within-home range scale using 16 years of data (2005–2020) from 329 females and 115 males in Norway. 3. We tested predictions related to the partial migration and sexual segregation theories using resource selection functions. We predicted higher selection for farmland by residents than by migrants, and higher selection by females than by males due to higher nutritional needs, but that higher perceived predation risk would impact their diurnal selection patterns. 4. The time spent on farmland was higher in winter (14%–18%) than in summer (8%–14%). Residents selected farmland more than migrants mainly at broad, landscape scale, while differences were smaller and less consistent at a fine, within-home range scale. Females showed higher broad-scale selection for farmland in winter, whereas males showed higher selection in summer. At a fine, within-home range scale, females selected farmland more in summer during darkness, whereas sex differences were small otherwise. The fine-scale selection of farmland was markedly higher during low-light conditions than in daylight. A high population density index was correlated with high broad-scale selection of farmland, i.e. high farmland availability in the home ranges, whereas the effect of the density index was weak at a fine, within-home range scale. 5. Our study emphasises how hypotheses deriving from the theories of partial migration and sexual segregation can improve our understanding of ungulates' selection of farmland. The higher selection by residents during summer highlights the importance of retaining landscape connectivity, allowing for migration and reducing pressure on local resources.

• Hjermann, Tilde Katrina Slotte; Rivrud, Inger Maren; Meisingset, Erling & Mysterud, Atle (2025). Multiple drivers of spring migration timing for red deer over the past 16 years in northern Europe. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 292(2038), s. 1–11. doi: 10.1098/rspb.2024.0842. Fulltekst i vitenarkiv Vis sammendrag

  The timing of migration is fundamental for species exploiting seasonally variable environments. For ungulates, earlier spring migration is expected with earlier vegetation green-up. However, other drivers, such as access to agricultural farmland and variation in local conditions, are also known to affect migration. We investigated the timing of spring migration for 96 male and 201 female red deer (Cervus elaphus) using a long-term dataset (2005–2020). Overall, the timing of migration was mainly characterized by large individual variability between and within years (95% range 6 April to 18 June). The spring migration timing was, as expected, later with colder winter and spring conditions (North Atlantic Oscillation (NAO) winter and April indices) and later peak vegetation green-up (NDVI), with a five-day delay in green-up causing a migration delay of 1.2 days. Timing was also influenced by local conditions in summer and winter home ranges. Red deer with greater access to farmland and a more variable topography (hence variable plant phenology) in winter delayed migration. Similarly, individuals with higher-elevation summer ranges (with delayed onset of plant growth) also delayed migration. Our analyses highlight that the timing of red deer migration is determined by multiple drivers affecting foraging conditions in the landscape, indicative of considerable phenotypic plasticity.

• Lelotte, Lucie; Panzacchi, Manuela; Johnson, Cheryl A.; Mysterud, Atle; Hansen, Brage Bremset & Niebuhr, Bernardo Brandão [Vis alle 13 forfattere av denne artikkelen] (2025). Population and habitat assessments for conservation: Comparing national strategies for Canadian boreal caribou and Norwegian wild reindeer. Global Ecology and Conservation. 61. doi: 10.1016/j.gecco.2025.e03668. Fulltekst i vitenarkiv Vis sammendrag

  Habitat loss and fragmentation are major threats to biodiversity. While essential, demographic data alone may be insufficient to rapidly detect habitat-driven population declines and identify efficient management actions. This study explores how conservation strategies can use and integrate demographic and environmental information to detect, monitor and counter population declines. By comparing two extensive conservation strategies for Rangifer tarandus in Canada and Norway, we draw key insights for more comprehensive and actionable strategies. Conservation strategies often use multicriteria approaches combining population and habitat metrics, but seldom succeed in formally integrating these through a causal understanding of habitat-population relationships. The Canadian strategy probabilistically assesses the viability of boreal caribou populations both through direct population modeling, and by statistically linking habitat disturbance to recruitment - thus indirectly capturing habitat-mediated changes in predator-prey dynamics and their consequences on caribou vital rates. The Norwegian strategy develops an expert-based approach to score the quality of wild reindeer populations by combining assessments of habitat quality, connectivity, demography, genetics and health. While the Norwegian assessment is more locally anchored and explores a wider range of drivers, the Canadian one is more targeted and provides a statistical conversion rate between habitat and population metrics. Both assessments serve as a basis for follow-up management actions. This study highlights the need to intensify research to quantify cumulative anthropogenic impacts on the loss of functionally connected habitat, and their consequences on population viability. This would enable early-warning systems for assessing population declines, and help shape more targeted prevention, mitigation and restoration actions

• Vindenes, Yngvild & Mysterud, Atle (2025). A seasonal matrix population model for ixodid ticks with complex life histories and limited host availability. Ecology. ISSN 0012-9658. 106(1). doi: 10.1002/ecy.4511. Fulltekst i vitenarkiv Vis sammendrag

  Many vector-borne diseases are sensitive to changes in land use and climate; hence, it is important to understand the factors that govern the vector populations. Ixodid ticks, which serve as vectors for multiple diseases, have a slow life cycle compared with many of their hosts. The observable questing population represents only a fraction of the total tick population and may include overlapping cohorts in each stage. The duration of each life stage (larvae, nymph, and adult) is variable and depends on factors such as the seasonal timing of questing, development, and host availability. Mathematical models are therefore essential to mediate how complex life cycle transitions and host interactions underpin the seasonal dynamics of the questing tick population. In this study, we develop a seasonal matrix population model for ixodid ticks feeding on a small and large host. The model has 17 stages representing the main life history stages (eggs, larvae, nymphs, and adults) combined with status of feeding, seasonal timing of feeding, and overwintering. The probability of finding a host depends on tick instar and host type, and density regulation is incorporated through limited host capacity. Using a life history representing Ixodes ricinus in Northern Europe as a baseline, we extract seasonal numbers of different parts of the tick population and calculate life history outcomes such as generation time and mean and variance of lifespan and of lifetime reproductive output. These results are compared with an alternative scenario of a southern life history. Secondly, we investigate (1) effects of seasonality in the small host availability on the seasonal numbers of tick stages and (2) effects of varying host availability and utilization of small versus large hosts by larvae and nymphs, on the seasonal numbers of questing ticks. Our results suggest that the small host availability is an important regulating factor through the feeding of larvae. Our model incorporates complex mechanisms underlying the seasonal composition of the tick population. It can be applied to different ixodid tick species and provides a framework for future investigations into intra- and interspecific variation in life history and population dynamics.

• Mysterud, Atle; Osnes, Magnus Nygård; Dean, Katharine Rose; Widgren, Stefan; Tranulis, Michael A. & Viljugrein, Hildegunn (2025). Modelling the effect of genotype (PRNP) linked to susceptibility, infection duration and prion shedding on chronic wasting disease dynamics of cervids. Ecological Modelling. ISSN 0304-3800. 509. doi: 10.1016/j.ecolmodel.2025.111253. Fulltekst i vitenarkiv Vis sammendrag

  Host genetics affect their susceptibility to pathogens and their ability to transmit infections (contagiousness). Chronic wasting disease (CWD) is a lethal prion disease of cervids with a wide distribution in North America, and with the first detection in Europe among reindeer in Norway in 2016. The PRNP gene, encoding the prion protein, has a strong impact on host susceptibility, and the duration and level of prion shedding. We developed a Susceptible-Exposed-Infectious-Dead (SEID) model to enhance our understanding of how PRNP genotype variation influences CWD dynamics. In a baseline model with only highly susceptible PRNP alleles, CWD prevalence reached a high level before the population collapsed. We sequentially introduced PRNP heterogeneity in susceptibility (Scenario 1), the duration of prion shedding (Scenario 2), and amount of prion shedding (Scenario 3). Heterogeneity in susceptibility alone (Scenario 1) led to a slow increase in CWD prevalence towards its peak, followed by a gradual decline and eventual epidemic die-out. Increasing the infection duration with constant shedding for the less susceptible PRNP genotypes (Scenario 2) led to a high and persistent CWD-prevalence level. When combining low-susceptibility PRNP alleles and increased duration of shedding but at lower levels (Scenario 3), the prevalence of CWD peaked slowly compared to the other scenarios. Hence, variation in PRNP allele composition can yield qualitatively different CWD epidemics among populations. Our ability to predict the longterm effects of CWD remains limited, primarily due to uncertainty about shedding patterns, environmental contamination, and other factors associated with PRNP-alleles that may limit selection.

• Mysterud, Atle; Moorter, Bram Van; Strand, Olav & Rolandsen, Christer Moe (2025). Hunting regulations and movements of alpine reindeer. Wildlife Biology. ISSN 0909-6396. doi: 10.1002/wlb3.01443. Fulltekst i vitenarkiv Vis sammendrag

  Most ungulate populations are regulated by hunting, and harvest rate is regulated through quotas and hunting season duration. Hunting is well known to affect behaviour of ungulates, but how annual variation in quotas and hunting season duration affects individual behaviour remains uncertain. Harvest rates reach their highest level when aiming to limit outbreaks of infectious diseases. In Norway, marked changes to hunting regulations of wild reindeer Rangifer tarandus were implemented as part of chronic wasting disease (CWD) management (2019‒2022) in the Hardangervidda population, Norway. Here, we quantify the movements (step length) of 135 female GPS-marked alpine reindeer during years (2001‒2022) with largely variable levels of quotas, harvest rates (0‒33%) and hunting season duration (31‒58 days). A strong predictor of movement was season with a decline from mid- August to early October, and longer and more variable movement distances during daytime compared to the night. Reindeer moved more in years with higher harvest rates, but mainly in late September and not in the beginning of the hunting season. Movements were higher during weekends, only in early September. Our study shows that responses to hunting of an alpine ungulate living in open habitat appear to differ from those of forest living ungulates. The high level of sociality of reindeer may further increase disturbance effects relative to less social and forest-dwelling species. Hunting season occurs at a critical time before the winter season in northern Europe, and further studies are needed to investigate whether increased movements during hunting affect body condition

• Rolandsen, Christer Moe; Kleven, Oddmund; Arntsen, Lina Gansmoe; Bergqvist, Göran; Davey, Marie Louise & Grøntvedt, Carl Andreas [Vis alle 13 forfattere av denne artikkelen] (2025). Using high-density SNP genotyping to determine the origin of wild boar dispersers outside the geographic range margins in Norway. Wildlife Biology. ISSN 0909-6396. 2025(5). doi: 10.1002/wlb3.01342. Fulltekst i vitenarkiv Vis sammendrag

  Mammalian dispersal is characterized by long-distance movements, and whether dispersal is sex-dependent and occurs at pre-saturation densities affects colonization speed and concurrent pathogen spread. In Scandinavia, Sweden classifies wild boar Sus scrofa as a native species and retains high densities, while Norwegian authorities considers it an alien invasive species and maintains the population at a minimum. With a long shared border and the recent detection of African swine fever (ASF) in Sweden, long-distance dispersal of wild boar into Norway is a concern. Using high-density single nucleotide polymorphism (SNP) analysis of relatedness among 192 wild boar distributed across Sweden and Norway, we report sex and determined the likely origin of seven dispersing individuals detected far outside of the current Norwegian range margins. Dispersal distances varied from 61 to 431 km (mean=230) and all seven dispersers were males, which reduces the likelihood of successful reproduction and establishment. Five of the wild boar originated from the low-density population at the colonization border in Norway, indicating pre-saturation dispersal. Sweden is of interest given the risk of pathogen spread. However, in the current epidemiological situation, we nevertheless consider it very unlikely that ASF will enter Norway by long-distance wild boar dispersal. African swine fever (ASF), dispersal, sex, SNPs, Sus scrofa, wild boar

• Mysterud, Atle; Flagstad, Øystein & Strand, Olav (2024). Feralization: A threat to conservation of wild reindeer. Conservation Science and Practice (CSP). 6(4). doi: 10.1111/csp2.13105. Fulltekst i vitenarkiv Vis sammendrag

  Conservation reintroduction is an increasingly applied tool for population restoration. The choice of source population is important from a conservation genetic perspective, but there is ambiguity in IUCN policies surrounding reintroductions from (semi-)domestic sources. After the depopulation of an entire wild reindeer population due to detection of chronic wasting disease in Norway, the plan is to re-establish reindeer after years of fallowing. Establishing wild reindeer has become challenging due to arguments for disease control favoring a semidomestic origin of the reintroduced stock. Selection is strong during domestication, and feralization does not lead to a full reversal towards wild traits. From a conservation perspective, we advocate future guidelines to include a ranking when wild, captive, semidomestic, and domestic stocks are available for reintroductions, in order to avoid feralization whenever possible during reintroductions and rewilding efforts.

• Hopp, Petter; Rolandsen, Christer Moe; Korpenfelt, Sirkka-Liisa; Våge, Jørn; Sörén, Kaisa & Solberg, Erling Johan [Vis alle 19 forfattere av denne artikkelen] (2024). Sporadic cases of chronic wasting disease in old moose – an epidemiological study. Journal of General Virology. ISSN 0022-1317. 105(1). doi: 10.1099/jgv.0.001952. Fulltekst i vitenarkiv Vis sammendrag

  Transmissible spongiform encephalopathies or prion diseases comprise diseases with different levels of contagiousness under natural conditions. The hypothesis has been raised that the chronic wasting disease (CWD) cases detected in Nordic moose (Alces alces) may be less contagious, or not contagious between live animals under field conditions. This study aims toinvestigate the epidemiology of CWD cases detected in moose in Norway, Sweden and Finland using surveillance data from 2016 to 2022. In total, 18 CWD cases were detected in Nordic moose. All moose were positive for prion (PrPres) detection in the brain, but negative in lymph nodes, all were old (mean 16 years; range 12–20) and all except one, were female. Age appeared to be a strong risk factor, and the sex difference may be explained by few males reaching high age due to hunting targeting calves, yearlings and males. The cases were geographically scattered, distributed over 15 municipalities. However, three cases were detected in each of two areas, Selbu in Norway and Arjeplog-Arvidsjaur in Sweden. A Monte Carlo simulation approach was applied to investigate the likelihood of such clustering occurring by chance, given the assumption of a non-contagious disease. The empirical P-value for obtaining three cases in one Norwegian municipality was less than 0.05, indicating clustering. However, the moose in Selbu were affected by different CWD strains, and over a 6 year period with intensive surveillance, the apparent prevalence decreased, which would not be expected for an ongoing outbreak of CWD. Likewise, the three cases in Arjeplog-Arvidsjaur could also indicate clustering, but management practices promotes a larger proportion of old females and the detection of the first CWD case contributed to increased awareness and sampling. The results of our study show that the CWD cases detected so far in Nordic moose have a different epidemiology compared to CWD cases reported from North America and in Norwegian reindeer (Rangifer tarandus tarandus). The results support the hypothesis that these cases are less contagious or not contagious between live animals under field conditions. To enable differentiation from other types of CWD, we support the use of sporadic CWD (sCWD) among the names already in use. Alces alces; epidemiology; Nordic countries; prion disease; sporadic chronic wasting disease (sCWD); transmissible spongiform encephalopathies.

• Mysterud, Atle; Tranulis, Michael A.; Strand, Olav & Rolandsen, Christer Moe (2024). Lessons learned and lingering uncertainties after seven years of chronic wasting disease management in Norway. Wildlife Biology. ISSN 0909-6396. doi: 10.1002/wlb3.01255. Fulltekst i vitenarkiv Vis sammendrag

  Chronic wasting disease (CWD) is well known among cervids in North America. Nevertheless, management faced different types and degrees of uncertainty when CWD was first detected in reindeer Rangifer tarandus in Nordfjella, Norway in 2016. We present a timeline of the efforts to control CWD, and identify how the process, measurement, environmental, and implementation uncertainties developed from the onset (2016) to the current situation (2023) after seven years of CWD management. In the ‘acute’ phase (2016–2019), political ambitions were high and depopulation of the Nordfjella reindeer area involving marksmen aimed at eradicating CWD. Subsequently, increased surveillance and increased male harvest was used to enable early detection or to achieve ‘freedom-from-CWD’ status of the adjacent populations. The second phase (2020-now) came when cases were detected in the large reindeer population in Hardangervidda. Management authorities postponed culling using marksmen, signifying an important change, with more emphasis on socio-political acceptance and consideration of the negative long-term consequences of conflicts with local stakeholders. The subsequent dialogue processes between scientists and local management ended in joint advice. However, the Ministry set aside all advice in 2022, halting further actions, after pressure and negative media attention. During this period, there was no clear research plan to increase knowledge of CWD to reduce process uncertainty; however, large surveillance investments were made to reduce measurement uncertainty. Despite this, detecting and estimating CWD among reindeer at low prevalence remains a key challenge. Governance challenges have emerged as significant implementation uncertainties, partly due to the uncertain occurrence of CWD. management uncertainty, prion diseases, prion protein gene (PRNP), prion strains, reindeer

• Mysterud, Atle; Davey, Marie Louise; Fossøy, Frode; Grøntvedt, Carl Andreas & Rolandsen, Christer Moe (2024). Using DNA metabarcoding to separate natural and human provided food in wild boar diet at the northern distribution range of Europe. Wildlife Biology. ISSN 0909-6396. doi: 10.1002/wlb3.01217. Fulltekst i vitenarkiv Vis sammendrag

  Wild boar Sus scrofa is increasing in numbers and extending its distribution across Europe and is difficult to control due to high reproductive potential. Dietary quality is a main determinant of wild boar population dynamics, and the extent to which they rely on human-provided food provide a key to limit their distribution. Yet, we lack data on wild boar diet from northern Europe. Here we use DNA-metabarcoding of faecal samples (n = 50) to determine wild boar diet during fall and winter in Norway. We mainly aimed to quantify the extent to which wild boar relies on natural or human-provided food sources. A secondary aim was to determine whether diet varies with individual characteristics (sex, age or weight), season (winter or fall), and between the two regions with wild boar in Norway. We found a high degree of diet variability between individuals. Individuals consuming high amounts of edible fungi consumed low amounts of plant material. The (heavier) male wild boars consumed 50% more human provided food than the (lighter) female wild boars. There was no clear effect of age, season (winter versus fall), or region on diet with the sample size available. The negative correlation between plants and fungi in each sample suggests that using multiple primers targeting different taxa can provide quantitative diet information, and points to an important role of fungi (truffles) during winter and fall. The large individual variation in diet may reflect opportunistic feeding tactics in Scandinavian boreal forests, driven by a lack of acorns and few crops. Our study has relevance for understanding limitations of wild boars at their northern distribution range in Europe, and thus also provides important information for management. baiting, diet, metabarcoding, mushrooms, supplemental feeding, wild boar

• Mysterud, Atle; Moorter, Bram Van; Viljugrein, Hildegunn; Andersen, Roy; Strand, Olav & Rolandsen, Christer Moe (2024). Evidence of limited short-term adverse demographic side effects of chronic wasting disease management. Journal of Wildlife Management. ISSN 0022-541X. doi: 10.1002/jwmg.22693. Fulltekst i vitenarkiv Vis sammendrag

  Competing objectives are common in the management of wildlife diseases. However, the extent to which disease mitigation conflicts with other goals has rarely been quantified. Chronic wasting disease (CWD) is a lethal cervid disease widely distributed in North America and recently detected in Europe. After the detection of CWD among reindeer (Rangifer tarandus) in Norway in 2016, intensified and male‐biased harvesting was used to manage CWD, but this may have adverse side effects. Based on extensive surveillance data (2001‒2022) gathered by the Norwegian Institute for Nature Research (NINA) and local management in addition to harvest statistics, we quantified how CWD management in Hardangervidda, Norway, changed harvest rates and affected population size, operational sex ratio, and age structure, and, in turn, whether recruitment, sex ratio of calves, and calving dates were affected. We used a formal reindeer quality standard to define adverse management. The estimated harvest rate of adult males reached >40% annually; however, the population size was only moderately reduced because the harvest of adult females was similar or decreased. The sex ratio changed from approximately 1:2.2 to 1:6.5 (males ≥3 years: females ≥1 year), which brought the population from good to poor quality according to the reindeer quality standard. The proportion of prime‐aged (≥5 years) males among adult males (≥2 years) in the harvest decreased from >60% to approximately 30%. Demographic changes led to limited side effects in the short‐term, with a delay of 4‒5 days in calving dates and a slightly more female‐biased sex ratio among the harvested calves but without a marked change in early recruitment. Wildlife populations are increasingly threatened by severe disease outbreaks that may require intensive management. Our study highlights the importance of extensive surveillance to document the potential adverse effects on population abundance, demography, and demographic side effects. The fairly limited short‐term adverse impacts can be traded against a higher likelihood of future sustainability without severe diseases; however, this may become an issue of concern if the disease becomes endemic. Balancing these trade‐offs would benefit from good communication between veterinary sciences and wildlife ecology experts. adverse side effects, cervids, environmental quality standard, Rangifer tarandus, reindeer, selective harvesting

• Goren, Asena; Mysterud, Atle & Vindenes, Yngvild (2024). Modeling the effects of phenological mismatch in tick questing and host demographic turnover on Lyme disease hazard. Ecological Modelling. ISSN 0304-3800. 498. doi: 10.1016/j.ecolmodel.2024.110910. Fulltekst i vitenarkiv Vis sammendrag

  Climate change is altering the seasonal abundance and activity patterns of ecologically interacting species. It is not yet known how changes in phenological alignment between ticks and their hosts will impact tick feeding, survival, and the timing and probability of pathogen transmission during feeding. It has been observed that the seasonal timing of human Lyme disease cases has shifted earlier, accompanying an increased incidence, which may reflect changes in tick questing phenology. We present a mathematical model framework for exploring the seasonal dynamics of a tick-borne pathogen. The model extends a recently developed seasonal population matrix model for ixodid ticks feeding on a small and a large host, to i) incorporate the transmission of a pathogen, based on the causative agent of Lyme disease, Borrelia burgdorferi sensu lato, between ticks and a reservoir-competent small mammal host, and ii) include seasonal demographic turnover in the small mammal host. Through modification of model parameters, we explored the effects of alternative scenarios for tick questing phenology, tick host selection, and seasonality of host reproduction on disease dynamics. Our model predicts that due to differences in their life history, seasonal infection prevalence is much more variable in the small mammalian host than in the tick vector. The rapid pace of host demographic turnover is important for clearing infection in the small mammal population. The alignment between the seasonal timing of host reproduction and tick questing phenology is a critical feature in the model, as it determines pathogen transmission and infection prevalence in host and vector populations. The model predicts that increased asynchrony between larval tick feeding and small host reproduction can increase the number of infected questing nymphs, a common metric for Lyme disease hazard. When larval tick feeding is misaligned with small host reproduction, the larvae feed predominantly on older hosts, which are more likely to be infected. Our model presents an adaptable framework for exploring seasonal relationships between pathogen dynamics, host demography, and vector life history traits in an emergent tick-borne disease system.

• Unsgård, Even; Meisingset, Erling L.; Rivrud, Inger Maren; Fossland, Gunn Randi; Thorvaldsen, Pål & Veiberg, Vebjørn [Vis alle 7 forfattere av denne artikkelen] (2024). An experimental assessment of biomass loss due to red deer (Cervus elaphus L.) grazing on agricultural grass meadows in Norway. European Journal of Wildlife Research. ISSN 1612-4642. 71(1). doi: 10.1007/s10344-024-01880-6. Fulltekst i vitenarkiv Vis sammendrag

  In Europe, over a third of the agricultural area is grass meadows used for livestock grazing and fodder production. Grass meadows provide a food source for wild ungulates causing human-wildlife conflicts due to forage removal. Few experimental studies have quantified biomass loss with enough replicates to determine how surrounding environments influences level of biomass removal. Using an exclosure experiment on 57 grassland meadows over five years at the northwest coast of Norway covering 10 650 km2, we quantified biomass removal by red deer (Cervus elaphus L.) and how environmental factors impacted biomass loss (Study 1). Furthermore, we examined development of biomass loss and crude protein concentration in five fields throughout the growing season (Study 2). The average predicted biomass loss to red deer grazing was 16% for the first harvest, and 7.3% for the second harvest (Study 1). Biomass loss increased with red deer density from 0% at the lowest density (0.6 red deer harvested/km2) to 31% at the highest density (4 red deer harvested/km2). Biomass loss increased from 12% to 32.8% as terrain ruggedness index (TRI) rose from 2.1 to 7.1. Absolute biomass loss increased towards time of grass harvest (Study 2). Crude protein concentration was higher in unfenced plots during the period before first harvest, but not between first and second harvest (Study 2). The quantification of biomass removal at a large spatial scale over several years in this study provides a better understanding of factors causing variation in losses.

• Figueiredo, Ana Manuel; Santín, Mónica; Köster, Pamela C.; Dashti, Alejandro; Maloney, Jenny G. & Torres, Rita [Vis alle 15 forfattere av denne artikkelen] (2024). Molecular detection and characterization of Blastocystis in herbivore livestock species in Portugal. Veterinary Parasitology. ISSN 0304-4017. 327. doi: 10.1016/j.vetpar.2024.110147. Fulltekst i vitenarkiv
• Lindsø, Lars; Viljugrein, Hildegunn & Mysterud, Atle (2024). Temporal increase in ticks and pathogen prevalence in the small mammal part of the Lyme disease cycle in northern Europe. Ecosphere. 15(11), s. 1–12. doi: 10.1002/ecs2.70063. Fulltekst i vitenarkiv Vis sammendrag

  Lyme disease is an emerging infectious disease and the most common vector-borne zoonosis in the northern hemisphere. The pathogen that causes Lyme disease in Europe is vectored by the generalist tick Ixodes ricinus, and the emergence of Lyme disease is partly linked to how climate warming affects tick distribution and abundance. However, we lack long-term data on tick infestations and infection prevalence in the main hosts involved in the transmission cycle. Here, we quantified the temporal trends (2014–2022) of I. ricinus infestations and the prevalence of Borrelia burgdorferi sensu lato in small mammalian hosts and linked annual variation to host abundance and climate in Norway. We found that tick infestations for both larvae (21% per year [95% CI 18–25]) and nymphs (18% [11–26]), and infection prevalence (14% [8–20]) increased over the period and were negatively associated with rodent abundance. Additionally, warmer years were associated with increased larval tick infestations on hosts. The combination of a temporal increase in both larval tick infestation and infection prevalence in hosts likely results in increased production of infected nymphs. Thus, we provide one mechanistic step toward understanding the Lyme disease emergence at northern latitudes of Europe. emerging infectious diseases, Lyme disease, small mammals, ticks

• Köster, Pamela C.; Figueiredo, Ana Manuel; Maloney, Jenny G.; Dashti, Alejandro; Bailo, Begoña & Torres, Rita [Vis alle 25 forfattere av denne artikkelen] (2024). Blastocystis occurrence and subtype diversity in European wild boar (Sus scrofa) from the Iberian Peninsula. Veterinary research (VR). ISSN 0928-4249. 55(1). doi: 10.1186/s13567-024-01385-9. Fulltekst i vitenarkiv Vis sammendrag

  The ongoing increase in wild boar populations across Europe has fostered human–wildlife conflicts, including the transmission of emerging pathogens with zoonotic importance. Blastocystis is a ubiquitous, faecal-oral transmitted protist that can cause gastrointestinal illnesses and is observed in humans and animals worldwide. The role of wildlife in the epidemiology of Blastocystis is insufficiently understood. Thus, we investigated the occurrence and subtype diversity of Blastocystis in free-ranging wild boars from the Iberian Peninsula using conventional PCR and next-generation amplicon sequencing of a fragment of the ssu RNA gene. A total of 459 wild boar faecal samples were collected across Spain (n = 360) and Portugal (n = 99) between 2014 and 2021. Blastocystis was present in 15.3% (70/459; 95% CI 12.1–18.9) of the wild boars analysed, and its occurrence was significantly higher in Portugal (34.3%, 34/99; 95% CI 25.1–44.6) than in Spain (10.0%, 36/360; 95% CI 7.1–13.6). Seven Blastocystis subtypes (ST5, ST10b, ST13–ST15, ST24b, and ST43) were detected among the surveyed wild boar populations, with greater variability detected in Portuguese samples. ST5 was identified in all the Blastocystis-positive animals, whereas 14.3% of them harboured ST mixed colonisations. Our results demonstrate that Blastocystis ST5 is particularly adapted to infect wild boars. The additional identification of zoonotic STs reinforces the role of wild boars as spreaders of zoonotic infections with public health significance.

• Atmeh, Kamal; Bonenfant, Christophe; Gaillard, Jean-Michel; Garel, Mathieu; Hewison, A. J. Mark & Marchand, Pascal [Vis alle 74 forfattere av denne artikkelen] (2024). Neonatal antipredator tactics shape female movement patterns in large herbivores. Nature Ecology and Evolution. 9, s. 142–152. doi: 10.1038/s41559-024-02565-8. Fulltekst i vitenarkiv Vis sammendrag

  Caring for newborn ofspring hampers resource acquisition of mammalian females, curbing their ability to meet the high energy expenditure of early lactation. Newborns are particularly vulnerable, and, among the large herbivores, ungulates have evolved a continuum of neonatal antipredator tactics, ranging from immobile hider (such as roe deer fawns or impala calves) to highly mobile follower ofspring (such as reindeer calves or chamois kids). How these tactics constrain female movements around parturition is unknown, particularly within the current context of increasing habitat fragmentation and earlier plant phenology caused by global warming. Here, using a comparative analysis across 54 populations of 23 species of large herbivores from 5 ungulate families (Bovidae, Cervidae, Equidae, Antilocapridae and Girafdae), we show that mothers adjust their movements to variation in resource productivity and heterogeneity according to their ofspring’s neonatal tactic. Mothers with hider ofspring are unable to exploit environments where the variability of resources occurs at a broad scale, which might alter resource allocation compared with mothers with follower ofspring. Our fndings reveal that the overlooked neonatal tactic plays a key role for predicting how species are coping with environmental variation.

• Hansen, Brage Bremset; Peeters, Bart; Flagstad, Øystein; Røed, Knut; Martin, Michael David & Jensen, Henrik [Vis alle 14 forfattere av denne artikkelen] (2024). Rapid loss of genetic variation and increased inbreeding in small and isolated populations of Norwegian wild reindeer. BioRxiv. ISSN 0362-4331. doi: 10.1101/2024.07.09.598942. Fulltekst i vitenarkiv
• Lindsø, Lars; Viljugrein, Hildegunn & Mysterud, Atle (2024). Vector competence of Ixodes ricinus instars for the transmission of Borrelia burgdorferi sensu lato in different small mammalian hosts. Parasites & Vectors. 17(1), s. 1–10. doi: 10.1186/s13071-023-06110-7. Fulltekst i vitenarkiv Vis sammendrag

  Background Many pathogens and parasites can infect multiple host species, and the competence of different hosts as pathogen reservoirs is key to understanding their epidemiology. Small mammals are important hosts for the instar stages of Ixodes ricinus ticks, the principal vector of Lyme disease in Europe. Small mammals also act as reservoirs of Borrelia afzelii, the most common genospecies of the Borrelia burgdorferi sensu lato (s.l.) spirochetes causing Lyme disease in Europe. However, we lack quantitative estimates on whether different small mammal species are equally suitable hosts for feeding I. ricinus and whether they show differences in pathogen transmission from host to tick. Methods Here, we analysed the feeding success and prevalence of B. burgdorferi s.l. infections in 12,987 instar I. ricinus found on captured small mammals with known infection status in Norway (2018–2022). Results We found that larvae were more likely to acquire a blood meal from common shrews (Sorex araneus, 46%) compared to bank voles (Myodes glareolus, 36%) and wood mice (Apodemus sylvaticus, 31%). Nymphs tended to be more likely to acquire a blood meal from wood mice (66%) compared to bank voles (54%). Common shrews harboured few nymphs (n=19). Furthermore, we found that larvae feeding on infected bank voles (11%) were more likely to be infected with B. burgdorferi s.l. than larvae on infected common shrews (7%) or wood mice (4%). Conclusions Our study provides quantitative evidence of differences in suitability for the instar stages of I. ricinus across taxa of small mammals and highlights how even known small mammal host species can differ in their ability to feed ticks and infect larval ticks with the pathogen causing Lyme disease. Graphical Abstract

• Anders, Jason Lee; Davey, Marie Louise; Moorter, Bram Van; Fossøy, Frode; Boessenkool, Sanne & Solberg, Erling Johan [Vis alle 9 forfattere av denne artikkelen] (2024). Elucidating nematode diversity and prevalence in moose across a wide latitudinal gradient using DNA metabarcoding. International Journal for Parasitology: Parasites and Wildlife. 24. doi: 10.1016/j.ijppaw.2024.100962. Fulltekst i vitenarkiv Vis sammendrag

  Parasitic nematodes are ubiquitous and can negatively impact their host by reducing fecundity or increasing mortality, yet the driver of variation in the parasite community across a wildlife host’s geographic distribution remains elusive for most species. Based on an extensive collection of fecal samples (n = 264) from GPS marked moose (Alces alces), we used DNA metabarcoding to characterize the individual (sex, age class) and seasonal parasitic nematode community in relation to habitat use and migration behavior in five populations distributed across a wide latitudinal gradient (59.6◦N to 70.5◦N) in Norway. We detected 21 distinct nematode taxa with the six most common being Ostertagia spp., Nematodirella spp., Trichostongylus spp., T. axei, Elaphostrongylus alces, and an unclassified Strongylida. There was higher prevalence of livestock parasites in areas with larger sheep populations indicating a higher risk of spillover events. The individual level nematode richness was mostly consistent across study areas, while the number and type of nematode taxa detected at each study area varied considerably but did not follow a latitudinal gradient. While migration distance affected nematode beta-diversity across all sites, it had a positive effect on richness at only two of the five study areas suggesting population specific effects. Unexpectedly, nematode richness was higher in winter than summer when very few nematodes were detected. Here we provide the first extensive description of the parasitic nematode community of moose across a wide latitudinal range. Overall, the population-specific impact of migration on parasitism across the distribution range and variation in sympatry with other ruminants suggest local characteristics affect hostparasite relationships. Alces alces Migration Habitat use Moose Nematode diversity

• Hjermann, Tilde; Bilet, Nikolai Antonsen; Rivrud, Inger Maren; Meisingset, Erling; Thorvaldsen, Pål & Mysterud, Atle (2024). Red deer grazing pressure on agricultural grass meadows from broad to local scale. Wildlife Biology. ISSN 0909-6396. s. 1–12. doi: 10.1002/wlb3.01312. Fulltekst i vitenarkiv Vis sammendrag

  Grazing by wildlife on agricultural land is widespread across geographical regions, and can cause human–wildlife conflicts due to reduced crop yield when the grazing pressure is high. Growing red deer (Cervus elaphus) populations in Europe call for an increased understanding of their grazing patterns to mitigate damages. We quantified how red deer grazing pressure (grazing presence and grazing level) on agricultural grass meadows (n = 60) in Norway varied across multiple spatial scales. We used a nested, hierarchical study design transcending from a broad scale (meadows across the landscape) to intermediate (between nearby meadows) and local (within-meadow) scales, allowing us to identify at which scale the variation in grazing pressure was strongest. We estimated how grazing was determined by broad-scale factors influencing forage availability and quality through population density, distance to coastline, and differences between the first versus second harvest, by intermediate-scale factors in terms of meadow management causing differences in botanical composition and quality, and by local-scale factors in terms of perceived predation risk and disturbance. At a broad scale, higher population densities were associated with higher grazing pressure, and more grazing occurred before the first compared to the second harvest. Intermediate-scale factors explained the most variation of grazing pressure from red deer, with higher grazing pressure on newly renewed meadows compared to other nearby meadows. On a local scale, more grazing occurred closer to the forest edge, providing cover, and further away from infrastructure, with increased risk and disturbance. Overall, our study highlights how drivers of grazing pressure on agricultural land vary across spatial scales. Population reductions on a broader scale may have some effect in reducing the grazing pressure, but renewed meadows will nevertheless attract red deer, causing higher grazing pressure compared to neighbouring meadows. This insight is crucial for determining effective mitigation strategies facing rising red deer populations across Europe.

• Baron, Jerome N.; Mysterud, Atle; Hopp, Petter; Rosendal, Thomas; Frössling, Jenny & Benestad, Sylvie L. [Vis alle 9 forfattere av denne artikkelen] (2024). Assessing freedom from chronic wasting disease in semi-domesticated reindeer in Norway and Sweden. Preventive Veterinary Medicine. ISSN 0167-5877. 229. doi: 10.1016/j.prevetmed.2024.106242. Fulltekst i vitenarkiv Vis sammendrag

  Establishing freedom from disease is a key component of surveillance and may have direct consequences for trade and economy. Transboundary populations pose challenges in terms of variable legislation, efforts, and data availability between countries, often limiting surveillance efficiency. Chronic wasting disease (CWD) is a contagious prion disease of cervids. The long incubation period and slow initial epidemic growth make it notoriously difficult to detect CWD in the early phase of an epidemic. The recent emergence of CWD in wild reindeer in Norway poses a threat to approximately 250,000 semi-domesticated reindeer in Norway and 250,000 in Sweden, including transboundary populations. Here, we provide a first analysis of surveillance data (2016–2022) from all reindeer districts in Norway and Sweden to determine the probability of freedom from CWD infection. During the six years, 6017 semi-domesticated reindeer were tested in Sweden and 51,974 in Norway. Most samples came from healthy slaughtered animals (low risk). Reindeer use large and remote areas and (high risk) samples from fallen stock and animals with clinical signs were difficult to obtain. A scenario tree model was run for seven different set of values for the input parameters (design prevalence within and between districts, probability of introduction, and relative risks) to determine the effect on surveillance sensitivity. At the national level, the mean probability of disease freedom was 59.0 % in Sweden and 87.0 % in Norway by 2021. The most marked effect on sensitivity was varying the design prevalence both within and between districts. Uncertainty about relative risk ratios affected sensitivity for Sweden more than for Norway, due to the higher proportion of animals in the high-risk group in the former (13.8 % vs. 2.1 %, respectively). A probability of disease freedom of 90 % or higher was reached in 8.2 % of the 49 districts in Sweden and 43.5 % of the 46 districts in Norway for a design prevalence of 0.5 %. The probability of freedom remained below 60 % in 29 districts (59.2 %) in Sweden and 10 districts (21.7 %) in Norway. At the national level, only Norway had a sufficiently large number of samples to reach a probability of more than 95 % of disease freedom within a period of 10 years. Our cross-border assessment forms an important knowledge base for designing future surveillance efforts depending on the spatial pattern of prevalence of CWD and risk of spread.

• Vindenes, Yngvild; Langvatn, Rolf & Mysterud, Atle (2023). Shifting seasonality of annual growth through ontogeny for red deer at northern latitudes. Ecosphere. 14(8), s. 1–11. doi: 10.1002/ecs2.4639. Fulltekst i vitenarkiv Vis sammendrag

  Large mammals at northern latitudes show annual cycles of body mass gain insummer and body mass loss in winter. The amplitude and seasonal timing ofthese cycles may vary through ontogeny depending on trade-offs towardinvestments in structural growth versus fat storage, reproduction, and futuresurvival. Despite this knowledge, there is no detailed model of how the season-ality of body mass develops through ontogeny. Here, we define a new seasonalgrowth model that accounts for shifting seasonality through two sine compo-nents: one included in the growth coefficient and the other on the asymptoticsize. We fitted 12 candidate models to longitudinal data on body mass of cap-tive male and female red deer (Cervus elaphus) in Norway, with different base-line growth structures (von Bertalanffy, Gompertz, and Brody) and includingzero, one, or both of the seasonal components. The best fitting model was theBrody model with both seasonal components included, allowing the annualpeak to shift through ontogeny: The annual peak occurred in December forcalves, shifting to November in yearlings, and October in 2- and 3-year-olds,ending with September for adults. All age classes showed an annual minimumat the end of winter around March. Males and females showed similar sea-sonal peaks through ontogeny, although males grow bigger and have largerseasonal amplitudes. Our new growth model provides a flexible framework tomodel seasonal growth changing through ontogeny, applicable to differentspecies. Brody, Gompertz, growth model, ontogenetic shift, red deer, seasonal growth, seasonality,ungulates, von Bertalanffy

• Lindsø, Lars; Anders, Jason Lee; Viljugrein, Hildegunn; Herland, Anders; Stigum, Vetle Malmer & Easterday, William Ryan [Vis alle 7 forfattere av denne artikkelen] (2023). Individual heterogeneity in ixodid tick infestation and prevalence of Borrelia burgdorferi sensu lato in a northern community of small mammalian hosts. Oecologia. ISSN 0029-8549. 203(3), s. 421–433. doi: 10.1007/s00442-023-05476-w. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Heterogeneous aggregation of parasites between individual hosts is common and regarded as an important factor in understanding transmission dynamics of vector-borne diseases. Lyme disease is vectored by generalist tick species, yet we have a limited understanding of how individual heterogeneities within small mammal host populations affect the aggregation of ticks and likelihood of infection. Male hosts often have higher parasite and infection levels than females, but whether this is linked to sexual body size dimorphism remains uncertain. Here, we analysed how host species, sex, and body mass influenced Ixodes ricinus tick infestations and the infection prevalence of Borrelia burgdorferi sensu lato (s.l.) in three species of small mammals involved in the enzootic transmission cycle of Lyme disease in Norway from 2018 to 2022. Larval and nymphal ticks were found on 98% and 34% of all individual hosts, respectively. In bank voles and wood mice, both larval and nymphal tick infestation and infection probability increased with body mass, and it increased more with mass for males than for females. Tick infestation in the common shrew increased with body mass and was higher in males, while pathogen infection was higher in females. Sex-biases in infestation did not correspond with level of sexual body mass dimorphism across species. This study contributes to our understanding of how individual heterogeneity among small mammalian hosts influences I. ricinus tick aggregation and prevalence of B. burgdorferi s.l. at northern latitudes.

• Figueiredo, Ana Manuel; Dashti, Alejandro; Santín, Mónica; Köster, Pamela C.; Torres, Rita & Fonseca, Carlos [Vis alle 16 forfattere av denne artikkelen] (2023). Occurrence and molecular characterization of Enterocytozoon bieneusi in wild and domestic animal species in Portugal. Medical Mycology. ISSN 1369-3786. 61(2), s. 1–14. doi: 10.1093/mmy/myad018. Fulltekst i vitenarkiv
• Mysterud, Atle; Rivrud, Inger Maren; Brekkum, Øystein & Meisingset, Erling L. (2023). Effect of legal regulation of supplemental feeding on space use of red deer in an area with chronic wasting disease. European Journal of Wildlife Research. ISSN 1612-4642. 69(1). doi: 10.1007/s10344-022-01630-6. Fulltekst i vitenarkiv Vis sammendrag

  Supplemental feeding of cervids during winter is a widespread management practice, but feeding may increase the risk of disease transmission. Therefore, legal regulations to limit supplemental feeding are often implemented when dealing with severe infectious diseases, such as chronic wasting disease (CWD) in cervids. However, it is currently unclear whether these regulations result in decreased spatial clustering and aggregation as intended. Supplemental feeding is expected to restrict the movement of cervids. Therefore, a ban on feeding may also result in wider space use and a risk of geographic spread of disease. The space use of 63 GPS-marked red deer (Cervus elaphus) was investigated before (n = 34) and after (n = 29) the implementation of a legal regulation aimed at limiting the supplemental feeding of cervids during winter in a CWD-affected region of Nordfjella, Norway. Snow depth was the main determinant of the space use for red deer. A moderate reduction in the number of GPS positions in spatial clusters was evident during periods of deep snow once the ban was in place. Sizes of core areas (Kernel 50%), home ranges (Kernel 95%), and dispersion (MCP 100%, number of 1 km2 pixels visited per deer) declined from January to March and with increasing snow depth. Dispersion (number of 1 km2 pixels visited per deer) did not depend on snow depth after the ban, and red deer used larger areas when snow depth was high after the ban compared to before. The ban on supplementary feeding had no effect on size of core areas or home ranges. Several potential factors can explain the overall weak effect of the ban on space use, including the use of agricultural fields by red deer, other anthropogenic feeding, and landscape topography. This study highlights that snow depth is the main factor determining space use during winter, and it remains to be determined whether the moderate reduction in spatial clustering during deep snow after the ban was sufficient to lower the risk of disease transmission.

• Goren, Asena; Viljugrein, Hildegunn; Rivrud, Inger Maren; Jore, Solveig; Bakka, Haakon & Vindenes, Yngvild [Vis alle 7 forfattere av denne artikkelen] (2023). The emergence and shift in seasonality of Lyme borreliosis in Northern Europe. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 290(1993). doi: 10.1098/rspb.2022.2420. Fulltekst i vitenarkiv Vis sammendrag

  Climate change has had a major impact on seasonal weather patterns, resulting in marked phenological changes in a wide range of taxa. However, empirical studies of how changes in seasonality impact the emergence and seasonal dynamics of vector-borne diseases have been limited. Lyme borreliosis, a bacterial infection spread by hard-bodied ticks, is the most commonvector-borne disease in the northern hemisphere and has been rapidly increasing in both incidence and geographical distribution in many regions of Europe and North America. By analysis of long-term surveillance data (1995–2019) from across Norway (latitude 57°580–71°080 N), we demonstrate a marked change in the within-year timing of Lyme borreliosis cases accompanying an increase in the annual number of cases. The seasonal peak in cases is now six weeks earlier than 25 years ago, exceeding seasonal shifts in plant phenology and previous model predictions. The seasonal shift occurred predominantly in the first 10 years of the study period. The concurrent upsurgence in case number and shift in case timing indicate a major change in the Lyme borreliosis disease system over recent decades. This study highlights the potential for climate change to shape the seasonal dynamics of vector-borne disease systems. seasonality, vector-borne zoonoses,disease ecology, Lyme borreliosis,Lyme disease, climate change, ecology, health and disease and epidemiology

• Mumme, Steffen; Middleton, Arthur D.; Ciucci, Paolo; De Groeve, Johannes; Corradini, Andrea & Aikens, Ellen O. [Vis alle 32 forfattere av denne artikkelen] (2023). Wherever I may roam—Human activity alters movements of red deer (Cervus elaphus) and elk (Cervus canadensis) across two continents. Global Change Biology. ISSN 1354-1013. 29(20), s. 5788–5801. doi: 10.1111/gcb.16769. Fulltekst i vitenarkiv Vis sammendrag

  Human activity and associated landscape modifications alter the movements of ani-mals with consequences for populations and ecosystems worldwide. Species perform-ing long-distance movements are thought to be particularly sensitive to human impact. Despite the increasing anthropogenic pressure, it remains challenging to understand and predict animals' responses to human activity. Here we address this knowledge gap using 1206 Global Positioning System movement trajectories of 815 individuals from 14 red deer (Cervus elaphus) and 14 elk (Cervus canadensis) populations spanning wide environmental gradients, namely the latitudinal range from the Alps to Scandinavia in Europe, and the Greater Yellowstone Ecosystem in North America. We measured individual-level movements relative to the environmental context, or movement ex-pression, using the standardized metric Intensity of Use, reflecting both the directional-ity and extent of movements. We expected movement expression to be affected by resource (Normalized Difference Vegetation Index, NDVI) predictability and topogra-phy, but those factors to be superseded by human impact. Red deer and elk movement expression varied along a continuum, from highly segmented trajectories over relatively small areas (high intensity of use), to directed transitions through restricted corridors (low intensity of use). Human activity (Human Footprint Index, HFI) was the strong-est driver of movement expression, with a steep increase in Intensity of Use as HFI increased, but only until a threshold was reached. After exceeding this level of impact, the Intensity of Use remained unchanged. These results indicate the overall sensitivity of Cervus movement expression to human activity and suggest a limitation of plastic responses under high human pressure, despite the species also occurring in human-dominated landscapes. Our work represents the first comparison of metric- based movement expression across widely distributed populations of a deer genus, contribut-ing to the understanding and prediction of animals' responses to human activity.

• Goren, Asena; Mysterud, Atle; Jore, Solveig; Viljugrein, Hildegunn; Bakka, Haakon & Vindenes, Yngvild (2023). Demographic patterns in Lyme borreliosis seasonality over 25 years. Zoonoses and Public Health. ISSN 1863-1959. 70(7), s. 647–655. doi: 10.1111/zph.13073. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Lyme borreliosis, the most common vector‐borne disease in Europe and North America, is attracting growing concern due to its expanding geographic range. The growth in incidence and geographic spread is largely attributed to climate and land‐use changes that support the tick vector and thereby increase disease risk. Despite a wide range of symptoms displayed by Lyme borreliosis patients, the demographic patterns in clinical manifestations and seasonal case timing have not been thoroughly investigated and may result from differences in exposure, immunity and pathogenesis. We analysed 25 years of surveillance data from Norway, supplemented by population demography data, using a Bayesian modelling framework. The analyses aimed to detect differences in case seasonality and clinical manifestations of Lyme borreliosis across age and sex differentiated patient groups. The results showed a bimodal pattern of incidence over age, where children (0–9 years) had the highest incidence, young adults (20–29 years) had low incidence and older adults had a second incidence peak in the ages 70–79 years. Youth (0–19 years) presented with a higher proportion of neuroborreliosis cases and a lower proportion of arthritic manifestations compared to adults (20+ years). Adult males had a higher overall incidence than adult females and a higher proportion of arthritis cases. The seasonal timing of Lyme borreliosis consistently occurred around 4.4 weeks earlier in youth compared to adults, regardless of clinical manifestation. All demographic groups exhibited a shift towards an earlier seasonal timing over the 25‐year study period, which appeared unrelated to changes in population demographics. However, the disproportionate incidence of Lyme borreliosis in seniors requires increased public awareness and knowledge about this high‐risk group as the population continues to age concurrently with disease emergence. Our findings highlight the importance of considering patient demographics when analysing the emergence and seasonal patterns of vector‐borne diseases using long‐term surveillance data.

• Tucker, Marlee A.; Schipper, Aafke M.; Adams, Tempe S.F.; Attias, Nina; Avgar, Tal & Babic, Natarscha L. [Vis alle 82 forfattere av denne artikkelen] (2023). Behavioral responses of terrestrial mammals to COVID-19 lockdowns. Science. ISSN 0036-8075. 380(6649), s. 1059–1064. doi: 10.1126/science.abo6499. Fulltekst i vitenarkiv Vis sammendrag

  COVID-19 lockdowns in early 2020 reduced human mobility, providing an opportunity to disentangle its effects on animals from those of landscape modifications. Using GPS data, we compared movements and road avoidance of 2300 terrestrial mammals (43 species) during the lockdowns to the same period in 2019. Individual responses were variable with no change in average movements or road avoidance behavior, likely due to variable lockdown conditions. However, under strict lockdowns 10-day 95th percentile displacements increased by 73%, suggesting increased landscape permeability. Animals' 1-hour 95th percentile displacements declined by 12% and animals were 36% closer to roads in areas of high human footprint, indicating reduced avoidance during lockdowns. Overall, lockdowns rapidly altered some spatial behaviors, highlighting variable but substantial impacts of human mobility on wildlife worldwide.

• Groeve, Johannes De; Weghe, Nico Van de; Ranc, Nathan; Morellet, Nicolas; Bonnot, Nadège C. & Gehr, Benedikt [Vis alle 13 forfattere av denne artikkelen] (2023). Back and forth: day–night alternation between cover types reveals complementary use of habitats in a large herbivore. Landscape Ecology. ISSN 0921-2973. 38, s. 1033–1049. doi: 10.1007/s10980-023-01594-1. Fulltekst i vitenarkiv Vis sammendrag

  Context The Complementary Habitat Hypothesis posits that animals access resources for diferent needs by moving between complementary habitats that can be seen as ‘resource composites’. These movements can occur over a range of temporal scales, from diurnal to seasonal, in response to multiple drivers such as access to food, weather constraints, risk avoidance and human disturbance. Within this framework, we hypothesised that large herbivores cope with human-altered landscapes through the alternate use of complementary habitats at both daily and seasonal scales. Objectives We tested the Complementary Habitat Hypothesis in European roe deer (Capreolus capreolus) by classifying 3900 habitat-annotated movement trajectories of 154 GPS-monitored individuals across contrasting landscapes. Methods We considered day-night alternation between open food-rich and closed refuge habitats as a measure of complementary habitat use. We frst identifed day–night alternation using the Individual Movement - Sequence Analysis Method, then we modelled the proportion of day–night alternation over the year in relation to population and individual characteristics. Results We found that day-night alternation is a widespread behaviour in roe deer, even across markedly diferent landscapes. Day–night alternation followed seasonal trends in all populations, partly linked to vegetation phenology. Within populations, seasonal patterns of open/closed habitat alternation difered between male and female adults, but not in juveniles. Conclusion Our results support the Complementary Habitat Hypothesis by showing that roe deer adjust their access to the varied resources available in complex landscapes by including diferent habitats within their home range, and sequentially alternating between them in response to seasonal changes and individual life history. Animal trajectories · Habitat use · IM-SAM · Resource composites · Roe deer · Sequential analysis methods · Spatio-temporal patterns · Vegetation green up

• Mysterud, Atle; Solberg, Erling Johan; Meisingset, Erling L.; Panzacchi, Manuela; Rauset, Geir Rune & Strand, Olav [Vis alle 9 forfattere av denne artikkelen] (2023). Estimating and managing broad risk of chronic wasting disease spillover among cervid species. Ecosphere. 14(9), s. 1–17. doi: 10.1002/ecs2.4663. Fulltekst i vitenarkiv Vis sammendrag

  The management of infectious wildlife diseases often involves tackling pathogens that infect multiple host species. Chronic wasting disease (CWD) is aprion disease that can infect most cervid species. CWD was detected in reindeer (Rangifer tarandus) in Norway in 2016. Sympatric populations of red deer(Cervus elaphus) and moose (Alces alces) are at immediate risk. However, the estimation of spillover risk across species and implementation of multispecies management policies are rarely addressed for wildlife. Here, we estimated the broad risk of CWD spillover from reindeer to red deer and moose by quantifying the probability of co-occurrence based on both (1) population density and(2) habitat niche overlap from GPS data of all three species in Nordfjella,Norway. We describe the practical challenges faced when aiming to reduce the risk of spillover through a marked reduction in the population densities of moose and red deer using recreational hunters. This involves setting the popu-lation and harvest aims with uncertain information and how to achieve them.The niche overlap between reindeer and both moose and red deer was low overall but occurred seasonally. Migratory red deer had a moderate niche over-lap with the CWD-infected reindeer population during the calving period, whereas moose had a moderate niche overlap during both calving and winter. Incorporating both habitat overlap and the population densities of the respective species into the quantification of co-occurrence allowed for more spatially targeted risk maps. An initial aim of a 50% reduction in abundance for the Nordfjella region was set, but only a moderate population decrease of less than 20% from 2016 to 2021 was achieved. Proactive management in the form of marked population reduction is invasive and unpopular when involving species of high societal value, and targeting efforts to zones with a high risk ofspillover to limit adverse impacts and achieve wider societal acceptance is important. disease management, host range, moose, multihost pathogens, niche overlap, Norway,population estimation, red deer, reindeer

• Figueiredo, Ana Manuel; Köster, Pamela C.; Dashti, Alejandro; Torres, Rita; Fonseca, Carlos & Mysterud, Atle [Vis alle 18 forfattere av denne artikkelen] (2023). Molecular Detection and Distribution of Giardia duodenalis and Cryptosporidium spp. Infections in Wild and Domestic Animals in Portugal. Transboundary and Emerging Diseases. ISSN 1865-1674. 2023. doi: 10.1155/2023/5849842. Fulltekst i vitenarkiv Vis sammendrag

  Enteric protozoan parasites Giardia duodenalis, Cryptosporidium spp., and, to a lesser extent, the ciliate Balantioides coli are responsible for severe human and animal intestinal disorders globally. However, limited information is available on the occurrence and epidemiology of these parasites in domestic, but especially wild species in Portugal. To fill this gap of knowledge, we have investigated G. duodenalis, Cryptosporidium spp., and B. coli occurrence, distribution, genetic diversity, and zoonotic potential by analyzing 756 fecal samples from several wild carnivores (n = 288), wild ungulates (n = 242), and domestic species (n = 226) collected across different areas of mainland Portugal. Overall, infection rates were 16.1% (122/756; 95% CI: 13.59–18.96) for G. duodenalis and 2.7% (20/756; CI: 1.62–4.06) for Cryptosporidium spp., while no ungulate sample analyzed yielded positive results for B. coli. Giardia duodenalis was found across a wide range of hosts and sampling areas, being most prevalent in the Iberian lynx (26.7%), the Iberian wolf (24.0%), and the domestic dog (23.9%). Cryptosporidium spp. was only identified in wild boar (8.4%), red fox (3.4%), Iberian lynx (3.3%), red deer (3.1%), and Iberian wolf (2.5%). Sequence analysis of G. duodenalis determined zoonotic assemblage A (subassemblage AI) in one roe deer sample, canine-specific assemblages C and D in Iberian wolf, red fox, and domestic dog, and ungulate-specific assemblage E in wild boar, sheep, cattle, and horse. Six Cryptosporidium species were identified: C. scrofarum in wild boar, C. canis in the Iberian wolf and red fox, C. ubiquitum in red deer and wild boar, C. felis in the Iberian lynx, and both C. ryanae and C. occultus in red deer. Giardia duodenalis and Cryptosporidium spp. coinfections were observed in 0.7% (5/756) of the samples. This is the first, most comprehensive, and largest molecular-based epidemiology study of its kind carried out in Portugal, covering a wide range of wild and domestic hosts and sampling areas. The detection of zoonotic Cryptosporidium spp. and G. duodenalis subassemblage AI demonstrates the role of wild and domestic host species in the transmission of these agents while representing a potential source of environmental contamination for other animals and humans.

• Mysterud, Atle; Viljugrein, Hildegunn; Andersen, Roy; Rauset, Geir Rune; Reiten, Malin Rokseth & Rolandsen, Christer Moe [Vis alle 7 forfattere av denne artikkelen] (2023). An infectious disease outbreak and increased mortality in wild alpine reindeer. Ecosphere. 14(3), s. 1–10. doi: 10.1002/ecs2.4470. Fulltekst i vitenarkiv Vis sammendrag

  Climate changes may lead to tipping points where the epidemiologicalcharacteristics of infectious wildlife diseases suddenly change, leading tooutbreaks. However, empirically documented cases of the extent to whichemerging infectious diseases (EIDs) affect populations of large vertebrates arefew, partly because of the limited surveillance of remote wildlife populations.EIDs may potentially lead to higher mortality than mean mortality levels. Here,we quantified the likely impact of digital necrobacillosis on the survivaland population dynamics of wild alpine reindeer (Rangifer tarandus)inHardangervidda National Park (NP), Norway. The outbreak of digitalnecrobacillosis in 2019 contributed to a decrease in the summer survival rate ofjuveniles to 51% compared to an average of 88% in 2005–2018 and 77% in 2020.However, since the outbreak mainly reduced juvenile survival, the impact onshort-term population dynamics was moderate, lowering the population growthrate (λ) before harvest from an average value of 1.18 (2005–2018) to 1.08 (2019)before harvest. In 2019, anomalous climate conditions with a high daily meantemperature combined with the highest recorded daily precipitation in late sum-mer were observed. Further studies are required to document the pathologicaldevelopment of digital necrobacillosis across demographic groups and proximateand ultimate causes of mortality. demography, digital necrobacillosis, disease ecology, National Park, population dynamics,reindeer, surviva

• Mysterud, Atle; Viljugrein, Hildegunn; Hopp, Petter; Andersen, Roy; Bakka, Haakon & Benestad, Sylvie L. [Vis alle 14 forfattere av denne artikkelen] (2023). Challenges and opportunities using hunters to monitor chronic wasting disease among wild reindeer in the digital era. Ecological Solutions and Evidence. 4(1). doi: 10.1002/2688-8319.12203. Fulltekst i vitenarkiv Vis sammendrag

  1. Surveillance of wildlife diseases poses considerable logistical challenges com-pared to that of humans or livestock. Citizen science can enable broader cover-age, but building an efficient disease monitoring system that relies on hunters is challenging. Chronic wasting disease (CWD) is a lethal and infectious prion dis-ease of cervids. Improving surveillance is important with the detection of CWD in wild reindeer (Rangifer tarandus) in Norway.2. This study describes the components of an efficient CWD monitoring sys-tem utilizing recreational hunters. We report the success of data capture after 6 years of surveillance. We provide an overview of CWD occurrence among the 24 wild reindeer areas and quantify the likelihood of disease absence in areas without detection.3. Surveillance aimed to test hunted reindeer aged ≥1 year. With higher quotas and extended hunting seasons, proactive surveillance was implemented in at-risk areas. There were several challenges of population demarcation and the lack of surveys required for risk- based sampling. Several specific tools for hunters have been developed, including digital apps for rapid reporting and feedback. Laboratory capacity was expanded, and novel statistical tools were developed for the specifics of the sampled tissues.4. The surveillance (2016–2021) achieved a sample return rate of 61.5% from a maximum of 22,123 harvested reindeer aged ≥1 year. Among these, 64.1% in-cluded both relevant tissues (retropharyngeal lymph nodes and brain), yielding 9412 (42.5%) complete samples of harvested reindeer. Samples originating from harvest constituted ~84% of total wild reindeer samples. 5. CWD was detected in 2 of the 24 wild reindeer management areas. The re-maining populations had a probability of CWD-freedom from 60% to 99% (mean= 77%) at a design prevalence of 0.5%.6. Utilizing hunters to monitor wildlife disease appears to be the most realistic op-tion for cervid species. However, the logistical and economic constraints are substantial and pose long-term challenges. Considerable uncertainty about dis-ease occurrence remains even after massive surveillance, and whether manage-ment should take preventive actions remains a challenge.cervids, citizen science, disease control, disease surveillance, freedom-from-disease, hunters, logistics, tissue sampling

• Davey, Marie Louise; Kamenova, Stefaniya; Fossøy, Frode; Solberg, Erling Johan; Davidson, Rebecca K. & Mysterud, Atle [Vis alle 7 forfattere av denne artikkelen] (2023). Faecal metabarcoding provides improved detection and taxonomic resolution for non-invasive monitoring of gastrointestinal nematode parasites in wild moose populations. Parasites & Vectors. 16(1). doi: 10.1186/s13071-022-05644-6. Fulltekst i vitenarkiv Vis sammendrag

  Background Although wild ungulate populations are heavily monitored throughout Europe, we understand little of how parasites afect population dynamics, and there is no systematic, long-term monitoring of parasite diversity and parasite loads. Such monitoring is in part hampered by a lack of time- and cost-efective assay methodologies with high sensitivity and good taxonomic resolution. DNA metabarcoding has been successfully used to characterize the parasitic nemabiome with high taxonomic resolution in a variety of wild and domestic hosts. However, in order to implement this technique in large-scale, potentially non-invasive monitoring of gastrointestinal parasitic nematodes (GIN), protocol optimization is required to maximize biodiversity detection, whilst maintaining time- and cost-efectiveness. Methods Faecal samples were collected from a wild moose population and GIN communities were characterized and quantifed using both parasitological techniques (egg and larva counting) and DNA metabarcoding of the ITS2 region of rDNA. Three diferent isolation methods were compared that difered in the volume of starting material and cell lysis method. Results Similar nematode faunas were recovered from all samples using both parasitological and metabarcoding methods, and the approaches were largely congruent. However, metabarcoding assays showed better taxonomic resolution and slightly higher sensitivity than egg and larvae counts. The metabarcoding was not strictly quantitative, but the proportion of target nematode sequences recovered was correlated with the parasitologically determined parasite load. Species detection rates in the metabarcoding assays were maximized using a DNA isolation method that included mechanical cell disruption and maximized the starting material volume. Conclusions DNA metabarcoding is a promising technique for the non-invasive, large-scale monitoring of parasitic GINs in wild ungulate populations, owing to its high taxonomic resolution, increased assay sensitivity, and time- and cost-efectiveness. Although metabarcoding is not a strictly quantitative method, it may nonetheless be possible to create a management- and conservation-relevant index for the host parasite load from this data. To optimize the detection rates and time- and cost-efectiveness of metabarcoding assays, we recommend choosing a DNA isolation method that involves mechanical cell disruption and maximizes the starting material volume. Nemabiome, Metabarcoding, ITS2, DNA extraction method, NC1–NC2 primers, Alces alces, Helminth, Ungulates

• Mysterud, Atle (2023). An epidemiological framework for chronic wasting disease in multihost communities. Journal of Applied Ecology. ISSN 0021-8901. 60(8), s. 1545–1550. doi: 10.1111/1365-2664.14441. Fulltekst i vitenarkiv Vis sammendrag

  1. Many pathogens can infect several host species, which complicates the management of wildlife diseases. Even for generalist pathogens, hosts are not equally competent, and variable niche overlap between hosts leads to different exposure levels within hosts when compared with that between hosts. Hence, the processes determining spillover risk and the subsequent transmission dynamics within and between species differ. 2. Chronic wasting disease (CWD) is a contagious prion disease of the cervids detected across expanded geographic ranges over the last few decades. Multihost management has become topical with CWD detection among reindeer Rangifer tarandus in Europe, with an immediate spillover risk to sympatric species. Here, I argue for the use of a community epidemiological framework that distinguishes between- and within-host dynamics arising from host competence and exposure processes. 3. In CWD, host competence is mainly determined by how variants of the prion protein gene (PRNP) affect susceptibility. The exposure level is not only linked to the density of infected and susceptible hosts both within and between species but also to the spatiotemporal niche overlap between species and social organization within species. 4. Mule deer Odocoileus hemionus and white-tailed deer Odocoileus virginianus are highly susceptible and expected to show true multihost dynamics; however, mule deer have a higher CWD prevalence in sympatric areas, indicating only partially linked dynamics. Moose Alces alces are highly susceptible, but cases of CWD-infected moose are few and appear to be spillover events with subsequent epidemic die outs. Elk Cervus canadensis have less susceptible PRNP variants and low levels of prion shedding in lymphoid tissues, indicating lower contagiousness. CWD prevalence in elk is lower and appears to result from spillover and subsequent within-species emergence, which is partially independent of sympatric deer. 5. Synthesis and applications. Stronger awareness of the different expected CWD dynamics within and between species may facilitate effective surveillance and management. Surveillance should consider the potential lack of linked dynamics between species when designing sampling. Multihost management can target niche overlap at different scales to limit spillover risk: (1) geographic distribution ranges, (2) density reductions in overlap zones and (3) co-use of transmission hot spots.

• Forsyth, David M.; Comte, Sebastien; Davis, Naomi E.; Bengsen, Andrew J.; Côté, Steeve D. & Hewitt, David G. [Vis alle 8 forfattere av denne artikkelen] (2022). Methodology matters when estimating deer abundance: a global systematic review and recommendations for improvements. Journal of Wildlife Management. ISSN 0022-541X. 86(4). doi: 10.1002/jwmg.22207. Fulltekst i vitenarkiv Vis sammendrag

  Deer (Cervidae) are key components of many ecosystems and estimating deer abundance or density is important to understanding these roles. Many field methods have been used to estimate deer abundance and density, but the factors determining where, when, and why a method was used, and its usefulness, have not been investigated. We systematically reviewed journal articles published during 2004–2018 to evaluate spatio-temporal trends in study objectives, methodologies, and deer abundance and density estimates, and determine how they varied with biophysical and anthropogenic attributes. We also reviewed the precision and bias of deer abundance estimation methods. We found 3,870 deer abundance and density estimates. Most estimates (58%) were for white-tailed deer (Odocoileus virginianus), red deer (Cervus elaphus), and roe deer (Capreolus capreolus). The 6 key methods used to estimate abundance and density were pedestrian sign (track or fecal) counts, pedestrian direct counts, vehicular direct counts, aerial direct counts, motion-sensitive cameras, and harvest data. There were regional differences in the use of these methods, but a general pattern was a temporal shift from using harvest data, pedestrian direct counts, and aerial direct counts to using pedestrian sign counts and motion-sensitive cameras. Only 32% of estimates were accompanied by a measure of precision. The most precise estimates were from vehicular spotlight counts and from capture–recapture analysis of images from motion-sensitive cameras. For aerial direct counts, capture–recapture methods provided the most precise estimates. Bias was robustly assessed in only 16 studies. Most abundance estimates were negatively biased, but capture–recapture methods were the least biased. The usefulness of deer abundance and density estimates would be substantially improved by 1) reporting key methodological details, 2) robustly assessing bias, 3) reporting the precision of estimates, 4) using methods that increase and estimate detection probability, and 5) staying up to date on new methods. The automation of image analysis using machine learning should increase the accuracy and precision of abundance estimates from direct aerial counts (visible and thermal infrared, including from unmanned aerial vehicles [drones]) and motion-sensitive cameras, and substantially reduce the time and cost burdens of manual image analysis.

Se alle arbeider i NVA

• Mysterud, Atle (2026). CWD og villreinforvaltning på Hardangervidda og i Nordfjella - hva har vi lært og hvordan ser fremtiden ut? Fulltekst i vitenarkiv
• Mysterud, Atle (2026). Hunting and management of chronic wasting disease in cervids in North America and Europe. Fulltekst i vitenarkiv
• Mysterud, Atle (2026). Ti år med skrantesyke: Hjalp det å skyte 2000 villrein? Fulltekst i vitenarkiv Vis sammendrag

  15. mars er det ti år siden det første tilfellet av skrantesyke ble oppdaget blant villrein. At 2000 villrein i Nordfjella ble skutt, skapte rystelser i norsk naturforvaltning. Hva har vi lært, og hvor står vi nå?

• Panzacchi, Manuela; Moorter, Bram Van; Stange, Erik; Simensen, Trond; Sydenham, Markus A. K. & Thorsen, Neri Horntvedt [Vis alle 13 forfattere av denne artikkelen] (2026). GreenPlan - Lansering av ny kartportal for Grønn Infrastruktur i Norge og samutvikling av støtteverktøy for arealprioritering, scenario- og konsekvensvurderinger. DEL1 - STATUS HJORT. Fulltekst i vitenarkiv
• Mysterud, Atle (2026). Adaptive management of chronic wasting disease in cervids. Fulltekst i vitenarkiv
• Andersen, Oddgeir; Veiberg, Vebjørn & Mysterud, Atle (2026). Gjennomgang av termisk undersøkelsen. Fulltekst i vitenarkiv
• Andersen, Oddgeir; Veiberg, Vebjørn & Mysterud, Atle (2026). Hvordan påvirker bruk av termisk utstyr antall observerte dyr? Fulltekst i vitenarkiv
• Meisingset, Erling L.; Hjermann, Tilde K. S.; Rivrud, Inger Maren & Mysterud, Atle (2025). Timing of spring migration and use of farmland in a partially migratory herbivore. Fulltekst i vitenarkiv
• Osnes, Magnus Nygård; Mysterud, Atle; Dean, Katharine Rose; Tranulis, Michael A.; Widgren, Stefan & Viljugrein, Hildegunn (2025). Modeling the effects of PRNP genotype linked to susceptibility, disease duration and prion shedding on chronic wasting disease dynamics of cervids. Fulltekst i vitenarkiv
• Osnes, Magnus Nygård; Mysterud, Atle; Dean, Katharine Rose; Tranulis, Michael A.; Widgren, Stefan & Viljugrein, Hildegunn (2025). Modeling the effects of PRNP genotype on chronic wasting disease dynamics of cervids. Fulltekst i vitenarkiv
• Mysterud, Atle (2025). Hunting and management of chronic wasting disease in reindeer. Fulltekst i vitenarkiv Vis sammendrag

  Chronic Wasting Disease (CWD) is a contagious prion disease of cervids, and groups with diseases like bovine spongiform encephalopathy in cattle, scrapie in sheep, and Creutzfeldt–Jakob disease in humans. Prion diseases are invariably fatal, and there are no vaccines or treatments available. CWD was first diagnosed in deer in 1967 in Colorado, USA, and has spread to 36 states in USA and 4 provinces of Canada infecting mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), elk (Cervus canadensis) and moose (Alces alces). The first detected case of CWD in Europe was in 2016 in a wild reindeer (Rangifer tarandus) in Norway. With onset of surveillance in Europe, a novel type of sporadic CWD, termed sCWD, was detected in moose and red deer (Cervus elaphus), but is not contagious and hence does not require hunting management. Contagious CWD has a long incubation period, where infected animals shed prions into the environment. Prevalence has reached high levels and led to deer population declines in North America, and management aims to avoid such a development in Norway. Hunting or culling is the main way both to monitor and control CWD. In Norway, the first area (Nordfjella) with CWD-detection in reindeer was depopulated, but this approach was not regarded possible when CWD was later detected in a larger reindeer population (Hardangervidda). Overall high harvest rate can limit CWD by shortening the infectious period, and prevalence of CWD is higher in adult males than adult females. Therefore, intensified male-biased harvesting is the primary CWD management tool implemented today. Current management can limit CWD but have a low(er) likelihood of CWD eradication. There is no long-term plan for how to control CWD in Norway.

• Mysterud, Atle; Rivrud, Inger Maren & Meisingset, Erling L. (2025). Hva betyr innmarka for hjorten, og hjorten for innmarka? Hjorteviltet. ISSN 1502-3729. Fulltekst i vitenarkiv
• Mysterud, Atle (2025). Hunting and management of chronic wasting disease in cervids in North America and Europe. Fulltekst i vitenarkiv
• Osnes, Magnus Nygård; Mysterud, Atle; Widgren, Stefan; Dean, Katharine Rose; Tranulis, Michael A. & Viljugrein, Hildegunn (2025). Modelling the effect of genotype (PRNP) linked to susceptibility, duration and level of prion shedding on chronic wasting disease dynamics of cervids. Fulltekst i vitenarkiv
• Unsgård, Even; Meisingset, Erling L. & Mysterud, Atle (2025). Store variasjoner i avlingstapet til hjort. NIBIO POP. ISSN 2464-1170. 11(55). Fulltekst i vitenarkiv Vis sammendrag

  Hjortebestanden i Norge har økt kraftig de siste ti årene, og den har ekspandert til nye områder. For hjorten er innmark et viktig habitat på grunn av mye og næringsrikt fôr. I områder med stor bestand kan beitetrykket på innmark være høyt. Dette forårsaker avlingstap, men det har vært usikkerhet knyttet til omfanget på større skala og hva som påvirker hvor omfanget er størst.

• Unsgård, Even; Meisingset, Erling L.; Rivrud, Inger Maren; Fossland, Gunn Randi; Thorvaldsen, Pål & Veiberg, Vebjørn [Vis alle 7 forfattere av denne artikkelen] (2025). Correction to: An experimental assessment of biomass loss due to red deer (Cervus elaphus L.) grazing on agricultural grass meadows in Norway. European Journal of Wildlife Research. ISSN 1612-4642. 71(1). doi: 10.1007/s10344-024-01887-z. Fulltekst i vitenarkiv
• Mysterud, Atle (2025). Vill - tam - forvillet - konsekvenser for villreinforvaltninga og reindrifta. Fulltekst i vitenarkiv
• Mysterud, Atle (2025). Adaptiv forvaltning av skrantesyke (adaptCWD). Fulltekst i vitenarkiv Vis sammendrag

  Atle Mysterud UiO, forteller om prosjektet der de ønsker å skaffe ny kunnskap og utvikle analytiske verktøy som muliggjør adaptiv forvaltning av CWD hos villrein i Nordfjella og på Hardangervidda. Utbruddet av skrantesyke (CWD) blant villrein i Norge utgjør en stor utfordring for norsk naturforvaltning. Det er stor usikkerhet om forekomst og effekter av ulike tiltak. Det er derfor krevende å balansere behovet for effektive tiltak for å begrense sykdommen, samtidig som tiltak kan være inngripende for villreinbestandene.

• Mysterud, Atle (2025). Forskningsstøtte til adaptiv forvaltning av skrantesyke (adaptCWD). Fulltekst i vitenarkiv
• Hansen, Brage Bremset; Rolandsen, Christer Moe; Strand, Olav; Tveraa, Torkild; Peeters, Bart & Mysterud, Atle (2024). Kvalitetsnormen - status og veien videre. Villreinen. ISSN 0801-6321. 2024, s. 10–13. Fulltekst i vitenarkiv Vis sammendrag

  Første runde av kvalitetsnormen er nå gjennomført for alle de 24 villreinområdene. De fleste har fått med seg at 6 av de 10 nasjonale områdene ble klassifisert til dårlig kvalitet. Det utløste oppfølging gjennom tiltaksplanarbeid. Nylig ble det kjent at også 6 av de øvrige 14 (ikke-nasjonale) områdene har dårlig kvalitet. Her er hovedårsaken små bestander med stort tap av genetisk variasjon. Det er nå viktig å gjennomføre kvantitative påvirkningsanalyser for bedre å forstå den relative betydningen av ulike årsaker til den dårlige kvaliteten og ulike utfordringer i både nasjonale og ikke-nasjonale villreinområder.

• Mysterud, Atle (2024). #AgriDeer: Damage and beyond: role of farmland for red deer populations. Fulltekst i vitenarkiv
• Köster, Pamela C.; Figueiredo, Ana M.; Maloney, Jenny G.; Dashti, Alejandro; Bailo, Begoña & Torres, Rita [Vis alle 25 forfattere av denne artikkelen] (2024). Erratum: Correction: Blastocystis occurrence and subtype diversity in European wild boar (Sus scrofa) from the Iberian Peninsula (Veterinary research (2024) 55 1 DOI: 10.1186/s13567-024-01385-9). Veterinary research (VR). ISSN 0928-4249. 55(1), s. 152–152. doi: 10.1186/s13567-024-01408-5. Fulltekst i vitenarkiv
• Rolandsen, Christer Moe; Strand, Olav; Romtveit, Lena; Mysterud, Atle & Andersen, Roy (2024). GPS-merking av villrein - Hvordan og til hvilken nytte. Fulltekst i vitenarkiv
• Lindsø, Lars; Viljugrein, Hildegunn & Mysterud, Atle (2024). Correction to: Vector competence of Ixodes ricinus instars for the transmission of Borrelia burgdorferi sensu lato in different small mammalian hosts (Parasites & Vectors, (2024), 17, 1, (23), 10.1186/s13071-023-06110-7). Parasites & Vectors. 17(1). doi: 10.1186/s13071-024-06249-x. Fulltekst i vitenarkiv
• Rolandsen, Christer Moe; Moorter, Bram Van; Strand, Olav; Andersen, Roy; Solberg, Erling Johan & Viljugrein, Hildegunn [Vis alle 7 forfattere av denne artikkelen] (2023). Bi-effekter av cwd-tiltak? Bukkeandel, alder, genetikk, skjeve kjønnsrater, kalvevekter, kalveproduksjon, dødelighet, forstyrrelser/arealbruk. Fulltekst i vitenarkiv
• Hansen, Brage Bremset; Rolandsen, Christer Moe; Mysterud, Atle; Rauset, Geir Rune; Andersen, Roy & Strand, Olav (2023). Assessing variability, trends and status of wild reindeer populations: the importance of long-term annual monitoring. Fulltekst i vitenarkiv
• Hansen, Brage Bremset; Mysterud, Atle; Rolandsen, Christer Moe; Rauset, Geir Rune & Strand, Olav (2023). Interactive threats and management dilemma: can habitat fragmentation help save the European wild reindeer? Fulltekst i vitenarkiv
• Strand, Olav; Mysterud, Atle; Rauset, Geir Rune; Hansen, Brage Bremset & Rolandsen, Christer Moe (2023). CWD in wild reindeer: Norway's responses to a new and much feared disease. Fulltekst i vitenarkiv
• Koutsoumanis, K.; Allende, A.; Alvarez-Ordonez, A.; Bolton, D.; Bover-Cid, S. & Chemaly, M. [Vis alle 24 forfattere av denne artikkelen] (2023). Monitoring of chronic wasting disease (CWD) (IV). EFSA Journal. ISSN 1831-4732. 21, s. 1–103. doi: 10.2903/j.efsa.2023.7936. Fulltekst i vitenarkiv Vis sammendrag

  The European Commission requested an analysis of the Chronic Wasting Disease (CWD) monitoring programme in Norway, Sweden, Finland, Iceland, Estonia, Latvia, Lithuania and Poland (9 January 2017–28 February 2022). Thirteen cases were detected in reindeer, 15 in moose and 3 in red deer. They showed two phenotypes, distinguished by the presence or absence of detectable disease-associated normal cellular prion protein (PrP) in lymphoreticular tissues. CWD was detected for the first time in Finland, Sweden and in other areas of Norway. In countries where the disease was not detected, the evidence was insufficient to rule out its presence altogether. Where cases were detected, the prevalence was below 1%. The data also suggest that the high-risk target groups for surveillance should be revised, and ‘road kill’ removed. Data show that, in addition to differences in age and sex, there are differences in the prion protein gene (PRNP) genotypes between positive and negative wild reindeer. A stepwise framework has been proposed with expanded minimum background surveillance to be implemented in European countries with relevant cervid species. Additional surveillance may include ad hoc surveys for four different objectives, specific to countries with/without cases, focusing on parallel testing of obex and lymph nodes from adult cervids in high-risk target groups, sustained over time, using sampling units and a data-driven design prevalence. Criteria for assessing the probability of CWD presence have been outlined, based on the definition of the geographical area, an annual assessment of risk of introduction, sustained minimum background surveillance, training and engagement of stakeholders and a surveillance programme based on data-driven parameters. All positive cases should be genotyped. Sample sizes for negative samples have been proposed to detect and estimate the frequency of PRNP polymorphisms. Double-strand sequencing of the entire PRNP open reading frame should be undertaken for all selected samples, with data collated in a centralised collection system at EU level.

• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe; Støen, Ole-Gunnar & Davey, Marie Louise [Vis alle 12 forfattere av denne artikkelen] (2023). Villsvin: Bestandsovervåking, GPS-merking og genetikk. Fulltekst i vitenarkiv
• Veiberg, Vebjørn; Andersen, Oddgeir; Zouhar, Yosra & Mysterud, Atle (2026). Bruk av termiske hjelpemidler under jakt – omfang og mulige effekter. Norsk institutt for naturforskning (NINA). ISSN 9788242656322. Fulltekst i vitenarkiv Vis sammendrag

  Gjennom de siste årene har det vært en rask økning i bruken av både håndholdte og våpenmonterte termiske hjelpemidler blant norske jegere, men omfanget har ikke vært tallfestet. Høsten 2025 ble det derfor gjennomført en spørreundersøkelse for å få mer kunnskap om hvordan disse hjelpemidlene påvirker jaktutøvelse, jakteffektivitet og datagrunnlaget som jegerne bidrar til innsamling av. Jegerne ble også bedt om å gi tilbakemeldinger om hvilke fordeler og utfordringer de så ved økt bruk av termiske enheter under jakt. Over 7000 personer deltok i spørreundersøkelsen. Jegere fra vestlandsfylkene og menn med lang jakterfaring var overrepresentert blant deltakerne i undersøkelsen. Omtrent to tredjedeler av mennene og halvparten av kvinnene oppga at de hadde benyttet termiske hjelpemidler. Hele 84 % av deltakerne som benyttet termisk spotter/kikkert, hadde startet å bruke dette i løpet av de siste fem årene. Blant deltakerne som benyttet termiske siktemidler, hadde 61 % av disse startet å bruke dette i samme tidsperiode. Blant respondentene var det klart flest personer som benyttet termiske hjelpemidler under hjortejakt, men også mange av jegerne som jaktet elg, rådyr og mindre rovdyr rapporterte at de brukte termiske enheter. Håndholdte termiske spottere og kikkerter var vanligere enn termiske siktemidler. Undersøkelsen omfattet over 5000 personer som hadde jaktet hjort de siste fem årene. Dette tilsvarer rundt 10 prosent av alle som jaktet hjort jaktåret 2023/2024. Termiske hjelpemidler ble særlig brukt ved posteringsjakt på innmark og ved speiding etter jaktbare dyr. Hele 63 % av respondentene mente teknologien bidro til økt sikkerhet, mens 8 % opplevde redusert sikkerhet. Omtrent halvparten svarte at termiske hjelpemidler hadde endret hvordan eller når de jaktet. De vanligste endringene var at jegerne var mindre avhengige av vær- og lysforhold, at de jaktet mer på natta eller at en større del av jakta skjedde på innmark. Hele 79 % av jegerne oppga at de observerte flere dyr ved bruk av termiske hjelpemidler. Samtidig avdekket undersøkelsen betydelige forskjeller i hvordan observasjoner og jaktinnsats registreres. Dette innebærer at både økende bruk av termiske hjelpemidler og ulik registreringspraksis representerer en stor utfordring for bruken av sett dyr-indeksene. Holdningene til håndholdte termiske hjelpemidler var gjennomgående positive. De viktigste fordelene som ble trukket frem var raskere oppdagelse av dyr, flere observasjoner, bedre oversikt og kontroll, tryggere skudd under dårlige lysforhold og bedre muligheter til å felle riktige dyr. Mange fremhevet også mer effektiv tidsbruk, større fleksibilitet og redusert behov for ettersøk som viktige fordeler. Motforestillingene mot termiske hjelpemidler var i hovedsak knyttet til etikk og jaktkultur. Mange mente at teknologien utfordrer prinsippet om at viltet skal ha en rimelig mulighet til å unngå jegeren, reduserer dyrenes ro om natten og svekker den sosiale dimensjonen ved jakt. Bekymringer knyttet til sikkerhet, feilvurderinger, skadeskyting og ulovlig jakt ble også trukket fram. Synet på bruken av våpenmonterte termiske siktemidler var delt, men et flertall av deltakerne i spørreundersøkelsen rapporterte bare om positive erfaringer. Blant respondentene med negative erfaringer knyttet til bruk av termiske enheter, var tema som sikkerhet, jaktkultur, mangelfull opplæring, tekniske begrensninger ved de termiske enhetene og omfang av feilskyting og ettersøk, de viktigste svarkategoriene. Undersøkelsen avdekker flere viktige kunnskapsbehov. Det mest sentrale er å avklare hvordan termiske hjelpemidler påvirker kvaliteten og tolkningen av sett hjort- og sett elg-data, samt sammenhengen mellom observasjonsindekser og reelle bestandsendringer. Det er også behov for mer kunnskap om hvordan teknologien påvirker jegernes uttak av dyr, både jakteffektivitet og kvotefylling. Videre bør det undersøkes om økt bruk av termiske hjelpemidler endrer tidspunktet og den geografiske fordelingen av fellinger, og om økt nattjakt påvirker hjortens arealbruk og atferd. Rapporten peker også på manglende kunnskap om effektene av termiske hjelpemidler ved jakt på andre arter, særlig arter som ikke forvaltes gjennom kvoter.

• Peeters, Bart; Burnett, Hamish Andrew; Mysterud, Atle; Tranulis, Michael A.; Jensen, Magnus Østgård & Jensen, Henrik [Vis alle 8 forfattere av denne artikkelen] (2026). Villreinbestandenes genetiske sårbarhet for skrantesjuke: Kartlegging og muligheter for genetisk overvåking. Norsk institutt for naturforskning (NINA). ISSN 9788242655479. Fulltekst i vitenarkiv Vis sammendrag

  Peeters, B., Burnett, H.A., Mysterud, A., Tranulis, M.A., Jensen, M.Ø., Jensen, H., Martin, M.D. & Hansen, B.B. 2026. Villreinbestandenes genetiske sårbarhet for skrantesjuke: kartlegging og muligheter for genetisk overvåking. NINA Rapport 2716. Norsk institutt for naturforskning. Skrantesjuke (Chronic Wasting Disease, CWD) ble påvist hos villrein i Nordfjella sone 1 i 2016, og seinere også på Hardangervidda. Det er behov for et styrket kunnskapsgrunnlag for risikovurdering og prioritering av forebyggende tiltak mot etablering og videre spredning av CWD. Denne rapporten kartlegger de norske villreinbestandenes genetiske sårbarhet for CWD ved å beskrive forekomsten av varianter i prionproteingenet (PRNP), og ved å utvikle en metodikk for å predikere PRNP genotyper fra genetiske data under arbeidet med kvalitetsnormen. Dette kan bidra til kostnadseffektiv genetisk overvåking av CWD. Vi sekvenserte PRNP genet til 660 individer fra 22 villreinområder. Disse individene var tidligere også genotypet på SNP arrayet som brukes i arbeidet med kvalitetsnormen. PRNP sekvensene var av tilstrekkelig kvalitet for 590 individer, og seks PRNP varianter (A F) ble bestemt fra sekvensdata. Basert på SNP arraydata valgte vi 122 SNP er på kromosom 11 innen et 1 megabase (Mb) vindu fra starten til PRNP genet og imputerte PRNP variantene med BEAGLE. Ti gangers kryssvalidering viste svært høy presisjon: 99,4 100 % samsvar mellom imputert og observert genotype (R² = 0,95 1,00). Feilratene var lave (falsk positiv 0,0 0,4 %; falsk negativ 0,0 5,6 %), og de største avvikene gjaldt den sjeldne varianten F. Datagrunnlaget økte til 1001 individer etter imputasjon av PRNP genotyper fra SNP arraydataene. De vanligste PRNP variantene var A (andel 0,42) og B (0,36), mens D (0,10) og E (0,09) var moderat vanlige, og C (0,01) og F (0,02) var sjeldne. Det er tidligere vist fra CWD positive dyr i Nordfjella og Hardangervidda at variant A og C er mer mottakelige for CWD enn B, D og E, mens mottakelighetsgrad for variant F er ukjent. Fordelingen av varianter viste en tydelig gradient knyttet til bestandenes genetiske innblanding fra tamrein: bestander med genetisk villreinopphav hadde høy frekvens av A, mens bestander med tamreinopphav hadde høyere frekvenser av mindre mottakelige varianter (særlig B, D og E). Variant F forekom utelukket i bestander fra Dovre Rondaneregionen. Vi beregnet en indeks for genetisk sårbarhet for CWD i villreinbestandene basert på tidligere funn fra Nordfjella og Hardangervidda, og fant en sterk negativ sammenheng mellom sårbarhet og genetisk likhet med tamrein (r = 0,89). Bestander med lavere genetisk sårbarhet kan i praksis fungere som en buffersone, for eksempel mellom Nordfjella og Dovre Rondaneregionen, ved å redusere sannsynligheten for trinnvis romlig spredning av smitte. Indeksen er et mål på genetisk predisposisjon for CWD og må tolkes sammen med smittepress, bestandstetthet, kontaktmønstre og miljøsmitte. Pågående smitteforsøk vil også kunne forbedre kunnskap om mottakelighetsgraden til de ulike variantene, og dermed gi grunnlag for å videreutvikle sårbarhetsindeksen og justere klassifiseringen. Vi viser også at fordelingen av PRNP genotyper i Nordfjella var tilnærmet lik mellom sone 1 (prøver tatt før og under bestandssanering) og sone 2. Reetablering av sone 1 med dyr fra sone 2 vil derfor neppe endre den opprinnelige genetiske sårbarheten for CWD, med mindre reetableringen inkluderer systematisk prøvetaking som gjør PRNP screening og eventuelt seleksjon av grunnleggerdyr mulig som risikoreduserende tiltak. Resultatene er relevante for både CWD overvåking og kvalitetsnormarbeidet, siden PRNP genotyper kan imputeres fra SNP arraydata som likevel skal samles inn jevnlig. Dette kan gi et kostnadseffektivt grunnlag for å vurdere endringer i genetisk predisposisjon for CWD som supplement til helseparameteren i delnorm 1. Videre kan resultatene inngå i sårbarhetsanalyser og i tiltaksplaner, hvor det må gjøres lokale avveiinger mellom tiltak som reduserer negative barriereeffekter og hensynet til å begrense trinnvis smittespredning.

• Rolandsen, Christer Moe; Moorter, Bram Van; Heim, Morten; Johnsen, Bjørnar; Mattisson, Jenny & Brealey, Jaelle C. [Vis alle 13 forfattere av denne artikkelen] (2026). Elgprosjektet i Oppland 2019-2024. Sluttrapport. Norsk institutt for naturforskning (NINA). ISSN 9788242652249. Fulltekst i vitenarkiv Vis sammendrag

  Rolandsen, C. M., Van Moorter, B., Heim, M., Johnsen, B., Mattisson, J., Brealey, J. C., Miller, A., Utaaker, K. S., Davidson, R. K., Grimsgaard, A., Mysterud, A., Wam, H. K., Solberg, E. J. 2026. Elgprosjektet i Oppland 2019–2024 – Sluttrapport. NINA Rapport 2416. Norsk institutt for naturforskning. Prosjektet ‘Elgen i Oppland’ ble igangsatt etter initiativ fra 11 kommuner og flere jaktrettshavere som helt eller delvis inngikk i tidligere Dokkfløy elgregion. Elgregionen omfattet en stor og delvis sesongtrekkende elgbestand i tidligere Oppland fylke, men som følge av uenigheter om årlig avskyting og uttak av trekkelg i vinterbeiteområdene ble regionsamarbeidet oppløst i 2013. Lokalt er det likevel et sterkt ønske om en felles forvaltning av elgstammen, og over lengre tid har det vært diskutert hvordan de ulike aktørene på nytt kan tilnærme seg et regionalt samarbeid. Det ble da tidlig påpekt behov for bedre og mer oppdatert kunnskap om elgens områdebruk i regionen, og etter en lengre prosess ble det besluttet å etablere et nytt elgmerkeprosjekt i området. NINA ble invitert med i prosjektutformingen, og gjennomførte senere prosjektet innenfor rammene gitt av en lokalt forankret styringsgruppe. I rapporten viser vi resultatene fra prosjektet som pågikk fra september 2019 til august 2024. Prosjektets overordnede mål har vært å øke kunnskapsgrunnlaget om elgen og beitegrunnlaget i tidligere Dokkfløy elgregion. Mer spesifikt var det et ønske å undersøke elgens trekkmønster og habitatbruk, samt å få bedre kunnskap om elgens kalveproduksjon og overlevelse. Dette er kunnskap som best kan oppnås ved å merke et representativt utvalg elg med GPS-sendere for deretter å studere disse individenes bevegelser, reproduksjon (antall fødte kalver) og overlevelse. I starten av prosjektperioden merket vi derfor 52 elger med GPS-sendere og fulgte disse inntil de døde, mistet halsbåndet eller vi aktiverte ‘drop-off’-mekanismen sommeren 2024. Alle elgene ble merket innenfor det mest markante nordlige (Murudalen, Sjodalen, Randsverk, Tesse, n = 36) eller sørlige (Gausdal Vestfjell, n = 16) vinterområde i regionen. Dette er områder med høye konsentrasjoner av elg vinterstid, hovedsakelig som følge av trekkende individer, og som derfor preges av høyt beitetrykk og beiteskader for skogbruket. I tillegg til merkestudiet undersøkte vi beitegrunnlaget og beitetrykket i regionen, og brukte jaktrelaterte data (sett og felt elg-data, slaktevekter) og trekkelgtellinger til å beskrive utviklingen i bestandstetthet, sammensetning og kalveproduksjon. Dette er viktig bakgrunnsinformasjon om bestand og næringsgrunnlag, og kan bidra til å forstå den romlige og tidsmessige fordelingen av elgen i området. Som et ledd i en langt større studie fra flere bestander analyserte vi også parasittforekomsten hos elgen i regionen og sammenlignet denne med tilstanden i andre bestander i Norge. Resultatene fra merkestudien viser at elgene i regionen beveger seg over store avstander og at områdebruken i svært liten grad holdt seg innenfor en kommune. Hele 86 % av de 51 elgene var sesongtrekkende, 14 % var stasjonære i minst ett år, mens kun ett individ ble klassifisert som stasjonær i begge år med data. De fleste individene brukte arealer i 4–5 kommuner (2–8) i løpet av et år. Gjennomsnittlig trekkdistanse var 47 km for elgkyr og 50 km for elgokser, men mange dyr hadde trekk på over 70–80 km mellom vinter- og sommerområder. Det lengste dokumenterte trekket var på 135 km i luftlinje – fra nordsiden av Vågåvatnet til Gjøvik. De sesongtrekkende individene beveget seg hovedsakelig mot sørøst på våren og tilbake mot nordvest på høsten. Mange av disse beveger seg da gjennom Espedalen, på grensen mellom Sør-Fron og Gausdal. Årlig registreres det her spor fra 600–800 elger på veg sørover fra Murudalen på våren (systematisk vårtelling utført langs fast transekt av lokalt mannskap), hvorav om lag to tredeler fortsetter gjennom Espedalen på sørvestsiden av vannet. Dalføret er relativt smalt, og trekkorridoren er sjeldent mer enn én kilometer bred. Også elgene i vinterbeiteområdet i Gausdal Vestfjell beveger seg mot sørøst på våren og tilbake mot nordvest på høsten, blant annet i dalføret ved Dokkfløyvatnet. Sesongtrekkene gjenspeiler elgens behov for å oppsøke sesongleveområder med gode forutsetninger for vekst og overlevelse. Vinterområdene i regionen kjennetegnes av mindre snø og mer lett tilgjengelig kvistbeite (særlig bjørk og furu), mens sommerområdene for det meste ligger lavere, har bedre feltsjikt og rikere tilgang på vier og dels rogn og selje. I tillegg er elgtettheten lavere i mange av sommerområdene, noe som reduserer konkurransen om ressursene. En slik kombinasjon av snøforhold, planteproduksjon og tetthetsavhengighet er trolig hovedforklaringen på hvorfor elgene gjennomfører så omfattende trekk. GPS-dataene viser samtidig at elgens bruk av vinterområder ikke er statisk mellom år. Ni (19 %) av de merkede individene skiftet vinterområde (mellom Murudalen og Gausdal) minst én gang i perioden 2020–2024, og skifte av vinterområde var høyest i et år med lite snø. Dette kan bety at fordelingen av vinterdyr mellom Murudalen og Gausdal påvirkes av snøforholdene, og at vintertetthet og belastningen på vinterbeitene kan variere mellom år. Det omfattende sesongtrekket og romlige variasjonen i vinterområdebruk fører til en skjev fordeling i elgrelaterte inntekter og kostnader mellom kommuner i regionen. Kommunene i nord bærer det meste av kostnader relatert til høyt beitepress og skogskader vinterstid, mens en større del av jaktuttaket skjer i kommuner lenger sør. GPS-dataene viser at opptil 75 % av merkelgen i nord trekker ut av kommunen på våren og returnerer først sent på høsten eller tidlig på vinteren, etter at jakta er gjennomført. Reell vintertetthet kan dermed være 3–4 ganger høyere enn elgtettheten under jakta i nord, og vil i enkelte år overstige den beregnede ernæringsmessige bæreevnen. Det faktum at tettheten og beitetrykket er større i vinterområdene enn i sommerområdene og der elgen befinner seg største delen av jakta kan medvirke til at bestanden holdes på et for høyt nivå i regionen. Ettersom kun et fåtall områder opplever svært høyt beitetrykk, vil mange av kommunene som hovedsakelig huser trekkelgen sommerstid ha liten grunn til å redusere sin del av bestanden. Høye bestandstettheter over tid kan imidlertid få konsekvenser også for elgen i sør da disse for en stor del befinner seg i de nordlige kommunene vinterstid. Dette kan ha bidratt til at elgens bestandskondisjon i regionen har svekket seg over tid. Åringsvektene har for eksempel falt med om lag 10–15 % de siste 15 årene, og kalverekrutteringen har vist en tydelig nedgang. En slik utvikling samsvarer med tetthetsavhengige mekanismer, men også med pågående klimaendringer og romlig variasjon i beitekvalitet. Jaktfelt med høyere andel jordbruksareal hadde høyere tvillingandel, noe som understøtter at mer produktive arealer gir bedre grunnlag for høy kalveproduksjon. Samlet peker dette mot en bestand der tetthet, klima og beitekvalitet virker sammen over tid, og der effektene akkumuleres i form av lavere kondisjon og redusert rekruttering. Ut fra lokalkunnskap, arkeologiske funn og tidligere radiomerkestudier var det ikke overraskende at de viktigste trekkorridorene i stor grad sammenfaller med kulturhistoriske spor etter fangstanlegg. Dette viser en lang kontinuitet i elgens trekkmønstre, der dagens trekk i stor grad følger de samme rutene som elgen har fulgt i århundrer og trolig opp til flere tusen år, og som ble utnyttet av mennesker til jakt og fangst. Særlig Espedalen og enkelte passasjer ved Dokkfløyvatnet har fungert som kanaliserende elementer på elgens sesongtrekk gjennom landskapet. Her konsentreres en stor andel av de trekkende elgene gjennom relativt trange dalfører og passasjer. Slike flaskehalser kan være særlig sårbare for inngrep, for eksempel veiutbygging, kraftutbygging, hyttefelt eller andre former for infrastruktur. Endringer i disse områdene kan få uforholdsmessig stor effekt på elgens sesongtrekk, både ved å gjøre trekket mer energikrevende og ved å øke risikoen for viltpåkjørsler og konflikter. Vi vet ikke hvor mye utbygging og menneskelig tilstedeværelse som tolereres før dette har store negative konsekvenser for elgtrekket. Fra et bevaringsperspektiv er det derfor viktig at den menneskelige arealbruken i området hensyntar elgens trekkveier og at nye inngrep ikke etableres i tilknytning til trekkorridoren. Funnene peker samlet sett på et tydelig behov for en regionalt samordnet og mer grenseoverskridende forvaltning, der jaktuttak, arealbruk, overvåking og trekkruter vurderes i sammenheng og ikke kommunevis eller hos enkeltgrunneiere. Dette kan innebære felles målsettinger for bestandsstørrelse og struktur, koordinert datainnsamling og tolkning av overvåkingsdata, og vern og tilrettelegging av sentrale trekkveier. En slik helhetlig tilnærming gir trolig bedre forutsetninger for å bevare det unike elgtrekket, opprettholde god bestandskondisjon, redusere uønskede skogskader og sikre et mer rettferdig og forutsigbart jaktuttak for kommunene i regionen.

• Hansen, Brage Bremset; Peeters, Bart; Røed, Knut; Flagstad, Øystein; Jensen, Henrik & Mysterud, Atle [Vis alle 8 forfattere av denne artikkelen] (2025). Genetikk i kvalitetsnorm for villrein: nye metoder gir nye muligheter. Norsk institutt for naturforskning (NINA). ISSN 9788242654410. Fulltekst i vitenarkiv Vis sammendrag

  Hansen, B.B., Peeters, B., Røed, K.H., Flagstad, Ø., Jensen, H., Mysterud, A., Rolandsen, C.M. & Strand, O. 2025. Genetikk i kvalitetsnorm for villrein: nye metoder gir nye muligheter. NINA Rapport 2619. Norsk institutt for naturforskning. Kvalitetsnormen for villrein ble utarbeidet for at villreinen (Rangifer tarandus tarandus) og villreinområdene skal kunne forvaltes iht. internasjonale forpliktelser, og for å nå nasjonale målsettinger om å ivareta levedyktige bestander innenfor deres naturlige utbredelsesområder. I kvalitetsnormens delnorm 1, bestandsforhold, inngår genetisk variasjon som en av måleparameterne. Genetisk variasjon er viktig for at arter og bestander bl.a. skal kunne tilpasse seg endringer i miljøet og håndtere utfordringer som sjukdommer og klimaendringer. Tap av genetisk variasjon og innavl er en kjent risiko ved fragmentering av leveområder, og spesielt for små bestander. Norsk villrein kjennetegnes av nettopp dette, samt genetisk innblanding fra tamrein. Norsk tamrein stammer ikke fra norsk villrein, og dette er problematisk i bevaringsbiologisk sammenheng. Vi rapporterer fra prosjektet Kvalitetsnorm for villrein – Datagrunnlag for genetikk i delnorm 1, gjennomført på oppdrag fra Miljødirektoratet. Prosjektet skulle etablere et solid datagrunnlag og utvikle forbedret metodikk for å vurdere genetisk variasjon. Oppdraget omfattet utarbeidelse av et forslag til revidert genetisk måleparameter. Denne skal være relativt enkel, relevant og robust over tid, og samtidig informativ og praktisk gjennomførbar. Arbeidet følger opp anbefalinger fra ekspertgruppa for kvalitetsnormen, som foreslo revisjon av genetikkparameteren i lys av overgang til bruk av et 625K Single Nucleotide Polymorphism (SNP)-array, som reflekterer variasjon i hele reinsdyrgenomet, for genetiske analyser. Prosjektet har gjennomført DNA-ekstraksjon og genotyping av eldre og nye prøver fra de 10 nasjonale villreinområdene. Tilsvarende data er tidligere produsert for de 14 ikke-nasjonale villreinområdene og inkluderes i denne rapporten. Forskjellige typer hår- og vevsprøver ble brukt. Til sammen har 1397 individer blitt genotypa, hvorav 778 og 580 individer i de nasjonale og ikke-nasjonale områdene, respektivt, samt 39 tamrein. 246 genotyper hadde for dårlig kvalitet til å inngå i analyser. Vi har analysert genetisk variasjon og tap av dette, endring i effektive bestandsstørrelser og innavlsnivå, samt bestandsstruktur og grad av genetisk villreinintegritet. Blant flere av de ikke-nasjonale villreinområdene har det vært et stort og raskt tap av genetisk variasjon, og noen har alarmerende lave effektive bestandsstørrelser og/eller høy og økende grad av innavl. Blant de nasjonale villreinområdene er hovedutfordringen genetisk innblanding fra tamrein (evt. rent tamreinopphav). Vi anbefaler at måleparameteren for genetikk endres, slik at den både inneholder vurderingskriterier for tap av genetisk variasjon, effektiv bestandsstørrelse og grad av genetisk innblanding fra tamrein. Vi anbefaler at ekspertgruppa som oppnevnes før neste kvalitetsnormklassifisering foretar en nøye videre vurdering av terskelverdier. Vi gir her anbefalinger om terskelverdier for tap av genetisk variasjon og effektive bestandsstørrelser. For fastsetting av terskelverdier på genetisk villreinintegritet/tamreininnblanding mangler det faglig grunnlag i litteraturen. Siden det er komplekse dilemmaer knyttet til om og i hvilken grad dette skal påvirke hvordan vi forvalter de 24 villreinområdene, overlater vi til den nye ekspertgruppa å ta stilling til terskelverdier. Ekspertgruppa kan også nedklassifisere den genetiske tilstanden hvis det dokumenteres større negative endringer i andre genetiske parametere, og de bør gjøre en helhetsvurdering av datagrunnlag, effektstørrelser, statistisk usikkerhet og årsaksforhold før endelig klassifisering. En forståelse av årsaksforhold vil kreve grundige kvalitative/kvantitative påvirkningsanalyser. Prosjektet inkluderer forslag til systematisering og langsiktig lagring av prøver og data, kvalitetssikring, samt tilrettelegging for framtidige klassifiseringsrunder. Vi gir en plan for prøveinnsamling, prøvelagring og datalagring, samt kostnadsoverslag. De totale kostnadene anslås til 1580 KNOK per klassifiseringsrunde f.o.m. 2030.

• Løland, Håkon Fossum; Mysterud, Atle; Rivrud, Inger Maren; Rolandsen, Christer Moe & Strand, Olav (2025). Salt lick use by wild reindeer with relevance for chronic wasting disease management on Hardangervidda, Norway. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Chronic Wasting Disease (CWD) is a prion disease in cervids, detected for the first time in Europe in 2016, in a wild reindeer (Rangifer tarandus tarandus) in Nordfjella, Norway. The disease is lethal and poses a serious risk to the species. Salt licks represent potential environmental transmission hotspots for CWD. On Hardangervidda, Norway, anthropogenic salt licks are widely used to supplement outfield grazing sheep (Ovis aries). This study investigates reindeer presence at various salt lick locations using 23 years of GPS data, analyzing visitation frequency both at the individual reindeer level and across different salt lick sites. I predicted that female reindeer would visit salt licks in spring and early summer more frequently than in the rest of the year and more frequently than males, due to increased demand for minerals during late gestation and lactation. I also predicted that overall salt lick use would be lower in winter, based on the assumption that sheep consume most of the salt during summer grazing. Lastly, I predicted a reduction in visitation to fenced salt lick sites, due to reduced accessibility. 37 % of the salt licks analyzed showed no recorded presence of reindeer within 200 meters. Among the remaining salt licks, reindeer usage was typically high at the start of the year, low during spring and summer, and increased toward the end of the year. There was no discernible difference between males and females regarding salt lick visitation patterns. However, an effect of fencing was found, with reindeer showing significantly less use of fenced salt licks, underscoring the effectiveness of this measure in mitigating disease transmission risk. While seasonal differences were observed, they did not align with my predictions. Moreover, the absence of sex-related differences also contradicted my prediction. These discrepancies may reflect either a different usage pattern of salt licks than expected or methodological limitations. Likely, reindeer visit salt licks only for brief periods, and the three-hour interval between GPS fixes used in this study may limit the precision in quantifying salt lick use. Given this constraint, future research could benefit from a methodology combining GPS data with camera trapping. A recent camera trap study on Hardangervidda reported no reindeer activity, but the study was conducted in an area appearing to be seldom used by reindeer. This highlights the importance of strategic site selection for effective fine-scale monitoring, which could be assisted by insights from GPS tracking. A combined approach could enhance understanding of salt lick use, such as visitation duration, further facilitating informed management practices to mitigate CWD transmission risks.

• Rosenquest, Louis Alexander; Mysterud, Atle; Rivrud, Inger Maren; Rolandsen, Christer Moe & Strand, Olav (2025). Patterns of salt lick visitation by red deer and its relevance for disease transmission. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Chronic wasting disease is a fatal prion disease, which may spread between cervid species. An infected environment poses a long term risk, even after infected individuals are gone, due to the durability of the prions in the environment. Artificial salt licks have been identified as potential “hotspots” for indirect transmission due to their role in aggregating animals. This study investigated red deer (Cervus elaphus) visitation at salt lick sites, in Nordfjella, Norway, where red deer overlap in space with formerly CWD infected reindeer (Rangifer tarandus). Camera trap data from 23 sites collected between 2017 and 2019 were analysed to assess how seasonal migration, sexual segregation, site management, and predation risk shape red deer visitation at artificial salt licks. Red deer visitation at the sites was strongly seasonal and followed predictions from migration patterns, with a peak during summer and almost no presence in winter. Topography influenced visitation patterns, reflected by the near absence of red deer above the tree line (>1200 m a.s.l.) and a later presence of salt licks at higher elevations consistent with seasonal migration patterns. There was different use of the salt licks by the sexes, with females predominating the observations. Males showed greater use of high elevation salt licks in spring and early summer, before migrating to lower elevations later in the season. Salt licks enclosed in fences received fewer red deer visits than unfenced sites, indicating that management can reduce the likelihood of CWD transmission and spillover. Red deer visitation peaked during twilight and nighttime, suggesting a behaviour shaped by perceived predation risk. This study highlights the influence of topography, sexual segregation, management and perceived risk of predation in the use of salt lick sites by red deer. The results provide insight relevant for targeted strategies to reduce potential CWD transmission and chances of spillover from reindeer to red deer at salt lick sites.

• Rivrud, Inger Maren; Odden, John; Davey, Marie Louise; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe & Støen, Ole-Gunnar [Vis alle 12 forfattere av denne artikkelen] (2024). Villsvin i Norge. Bestandsovervåking: Utbredelse, områdebruk og diett. Norsk institutt for naturforskning (NINA). ISSN 9788242652607. Fulltekst i vitenarkiv Vis sammendrag

  Villsvin, Sus scrofa, overvåking, utbredelse, kamerafeller, viltkamera, områdebruk, bevegelsesmønstre, radiomerking, diett, DNA-metastrekkoding, afrikansk svinepest, SCANDCAM, Norge

• Mysterud, Atle; Tranulis, Michael A.; Strand, Olav & Rolandsen, Christer Moe (2024). Erfaringer og usikkerheter etter 7 år med skrantesyke (CWD) i Norge. En litteraturgjennomgang. Norsk institutt for naturforskning (NINA). ISSN 9788242652102. Fulltekst i vitenarkiv Vis sammendrag

  Nordfjella Hardangervidda Villrein Hjortedyr Skrantesyke CWD Forvaltning Litteraturgjennomgang

• König, Emilie; Mysterud, Atle; Rivrud, Inger Maren & Lindsø, Lars (2024). Using camera trapping to estimate small mammal occurrence. Universitetet i Oslo. Fulltekst i vitenarkiv
• Lindsø, Lars; Mysterud, Atle; Viljugrein, Hildegunn; Rivrud, Inger Maren & Anders, Jason Lee (2024). The role of small mammals in the enzootic cycle of Lyme disease in northern Europe. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Small mammals are important hosts to Ixodes ricinus larvae and maintain natural reservoirs of Borrelia afzelii, the most common genospecies of Borrelia-bacteria that causes Lyme disease in Europe. In my PhD project, I aimed to provide quantitative data on the role of small mammals as hosts to I. ricinus ticks and Borrelia-reservoirs to aid our understanding of Lyme disease emergence in northern Europe. By using data on pathogen infection in captured small mammals and their harboured ticks from Son, Vestby (2014-2022), I found that both tick infestations and pathogen infection prevalence in hosts increased markedly during the study period. The increase indicates a corresponding increase in the production of infected tick nymphs from fed and infected larvae, which in turn is directly linked to Lyme disease hazard for humans. Moreover, I found positive effects of warm years on the number of ticks on small mammals and that the proportion of infected hosts were lower in peak rodent years. Taken together, my thesis provides quantitative field-based evidence on the role of rodents and shrews in the Lyme disease cycle in northern Europe and provides important insights to explain the Lyme disease emergence in northern Europe in the last decades.

• Mysterud, Atle; Rivrud, Inger Maren; Meisingset, Erling & Hjermann, Tilde K. S. (2024). Habitat selection, migration timing, and grazing patterns of red deer in an agroecosystem. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Agriculture has significantly impacted the land use over the past centuries. For wild herbivores such as the red deer, foraging on farmland can be beneficial when food is limited in their natural habitats. In Norway, the red deer populations consist of migratory and resident individuals, where migrants travel from low-elevation winter ranges, typically with more available farmland, towards higher-elevation summer ranges. Residents remain in the low-elevation areas year-round. I found that residents selected farmland more than migrants, buffering the migrants’ benefit from following the wave of emerging vegetation in spring. Higher farmland availability also delayed the red deer’s spring migration, that generally varied greatly between and within years. Wildlife foraging on farmland can cause conflicts with humans due to reduced crop yield. Grazing can vary with factors on different scales, and I found most variation in grazing between neighbouring meadows, with more grazing on those recently renewed. Within meadows, more grazing was found close to the forest and away from infrastructure. On broad scale, grazing increased with population density. My thesis provides insight into the coupled dynamics of the red deer and agricultural farmlands, which can be important for management of this coupled ecosystem.

• Rolandsen, Christer Moe; Våge, Jørn; Hopp, Petter; Benestad, Sylvie L.; Viljugrein, Hildegunn & Solberg, Erling Johan [Vis alle 14 forfattere av denne artikkelen] (2023). Kartlegging og overvåking av skrantesjuke (chronic wasting disease - CWD) 2022. Norsk institutt for naturforskning (NINA). ISSN 9788242650740. Fulltekst i vitenarkiv Vis sammendrag

  Norge, skrantesjuke, CWD, klassisk CWD, atypisk CWD, hjortedyr, elg, hjort, rådyr, villrein, tamrein, kartlegging

• Stien, Jenny; Mattisson, Jenny; Hansen, Inger; Kleven, Oddmund; Randby, Åshild Taksdal & Loe, Leif Egil [Vis alle 9 forfattere av denne artikkelen] (2023). Kongeørn som skadevolder på lam på Fosen. Norsk institutt for naturforskning (NINA). ISSN 9788242651068. Fulltekst i vitenarkiv Vis sammendrag

  Kongeørn Aquila chrysaetos, Havørn Haliaeetus albicilla, sau Ovis aries, tap av sau på utmarksbeite, sykdom i sau, GPS, DNA, rovdyr-husdyr, konflikter

• Bilet, Nikolai Antonsen; Mysterud, Atle; Rivrud, Inger Maren; Meisingset, Erling L. & Hjermann, Tilde K. S. (2023). Spatial grazing patterns of red deer in agricultural meadows. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  The size of the Norwegian red deer population is historically high and typical of the trend seen over much of Europe. Dense populations may cause damage to agricultural crops, and crop yield is drastically decreased by red deer grazing in certain areas. We know that red deer select actively managed meadows, i.e., frequently renewed by fertilisation and re-seeding, over other agricultural meadows. Despite its importance, information regarding spatial grazing patterns by red deer on agricultural meadows is limited. In this study, I aim to quantify how grazing on agricultural meadows by red deer varies across spatial scales in southwest Norway. I hypothesise that grazing on agricultural meadows is determined by three major effects: (H1) Factors affecting forage quality and availability in meadows relative to natural habitats, such as population density and seasonal change, (H2) meadow management, such as renewal of meadows, and (H3) perceived predation risk and human disturbance, such as distance to settlement and forest edge. Grazing levels were assessed across meadows in a hierarchical study design, and I analysed the data using a binary logistic regression that model absence of grazing and a beta regression that model the level of grazing given grazing occurred. This enabled me to quantify both variation among spatial hierarchical units and the mechanisms behind spatial grazing patterns. I found that the grazing variation was largest between meadows in the local area and smallest on broader scale. High red deer density areas received more grazing relative to low-density areas, more grazing occured when meadow grass was shorter, and early in summer relative to late, suggesting that red deer select meadows over natural habitat when the difference in quality and availability of forage are large enough. Newly refreshed meadows received more grazing than the older ones, implying that a large part of the local site effect was caused by meadow management. Evidence of trade-off effects also appeared important as spatial grazing patterns changed near roads, houses, and forests. Broad-scale variation in red deer density explained some of the variations in grazing. However, since the largest variation in grazing was found locally, population reduction at broad scales may not effectively lower damages. These results may affect the scale at which management should target mitigation efforts.

• Fjeld, Madelen Cecilia Espino; Mysterud, Atle; Rivrud, Inger Maren; Meisingset, Erling L. & Hjermann, Tilde K. S. (2023). Estimering av kalving og kalvingstidspunkt for hjort ved bruk av GPS-data. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  Et essensielt tema innen økologi er at oppfostring av avkom hos mange arter krever tilgang på betydelige ressurser og at fødselstidspunktet synkroniseres for å treffe toppen til ressurstilgangen i sesongmessige miljøer. Dagens raske klimaendringer mot for eksempel høyere temperaturer og en tidligere vår i nordlige økosystemer, har ført til at mange planter har vist trender for tidligere fenologiutvikling. For plantespisende pattedyr kan dette føre til trofisk «mismatch» mellom tidspunkt for fødsel og den fenologiske utviklingen hos beiteplantene, og vil kunne føre til at fødselstidspunktet ikke lenger treffer tidspunktet med optimal tilgang på ressurser. Endring i de klimatiske faktorene kan føre til seleksjon for tidligere eller senere fødselstidspunkt. For hjortedyr har tidspunkt for brunst og parring påvirkning på kalvingstidspunktet, og en høyere bestandstetthet hos enkelte arter kan føre til senere unnfangelse. Få tidligere undersøkelser har dokumentert om kalvingstidspunktet til hjortedyr er blitt endret over tid. En av årsakene til dette er mangel på data, siden det er vanskelig å observere kalving og kalvingstidspunkt i skogsområder. På grunn av en endret atferd til hjortedyr under kalving, er det hos enkelte arter vist at det er mulig å sannsynliggjøre oppdagelse av kalving ved bruk av ny teknologi (posisjonsdata fra GPS-halsbånd). Målet for dette prosjektet var å undersøke om posisjonsdata kan brukes til å påvise kalving og kalvingstidspunkt hos hjort (Cervus elaphus), og deretter bruke metoden for å undersøke om kalvingstidspunktet har endret seg over tid og med bestandstetthet i Norge. I analysene ble det brukt GPS-data fra 188 hjort og 309 mulige kalvingshendelser fra perioden 2005-2021 fra Trøndelag og Møre og Romsdal i Norge. Tjue koller med observert kalvingstidspunkt ble brukt som utgangspunkt for endringspunktanalyse og maskinlæring, for å finne estimert kalvingstidspunkt og -status ved hjelp av kovariater knyttet til bevegelsesmønster. Observert og estimert kalvingsstatus ble sammenlignet, men det var kun 81% av kollene som ble riktig estimert, som var et svakere resultat enn forventet. Når metoden ble brukt på et større utvalg av hjort, var det ikke mulig å påvise klare trender i kalvingstidspunkt over tid, men dette kan skyldes svakheter med metoden. Hjorten er en art som har en gjemmer-strategi første uken etter kalving. Den intensive perioden rett etter kalving er kort for en gjemmer som fører til utfordringer ved deteksjon av kalvingshendelser, og maskinlæringsmetodene bør derfor utvikles ytterligere for å få sikrere resultater. Dette vil være et viktig tema med tanke på hvordan klimaendringer kan påvirke det fremtidige økologiske samspillet.

Se alle arbeider i NVA