ingermri

• Breen, Catherine M.; Odden, John; Linnell, John Durrus; Thorsen, Neri Horntvedt; Rivrud, Inger Maren & Lundquist, Jessica D. [Show all 7 contributors for this article] (2026). Diel and seasonal cycles of snow hardness predict changes in activity patterns for roe deer but not mountain hares. Canadian Journal of Zoology. ISSN 0008-4301. 104. doi: 10.1139/cjz-2025-0165. Full text in Research Archive Show summary

  The resistance of the snow surface to penetration, or snow hardness, is an important factor affecting wildlife movement. Snow hardness can change dramatically over the course of the day, but it is unknown how animals respond to temporal changes in snow hardness. Using 260 hourly sinking depth measurements as indices of surface hardness along a latitudinal gradient in Norway, we quantified diel cycles of snow hardness in relation to environmental variables. Time relative to sunrise and sunset, temperature, canopy cover, and snow density were the best predictors of surface hardness ( R 2  = 0.57). We matched diel cycles of the predicted surface hardness index to diel activity in roe deer ( Capreolus capreolus (Linneaus, 1758)) and mountain hares ( Lepus timidus Linneaus, 1758), using data from the large-scale Scandcam camera-trap network in Norway from 2017 to 2023 ( n = 698 cameras). Roe deer increased morning activity when the snow was harder and deeper, and hares did not show diel shifts in relation to the snow hardness index and preferred softer snow at higher snow depths. As snow conditions and wintertime temperatures continue to change, this study highlights the importance of diel activity adaptations to environmental conditions.

• 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. Full text in Research Archive Show summary

  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.

• 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), p. 2655–2670. doi: 10.1111/1365-2656.70163. Full text in Research Archive Show summary

  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. Full text in Research Archive Show summary

  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.

• 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), p. 884–895. doi: 10.1111/1365-2656.70017. Full text in Research Archive Show summary

  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), p. 1–11. doi: 10.1098/rspb.2024.0842. Full text in Research Archive Show summary

  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.

• Rolandsen, Christer Moe; Kleven, Oddmund; Arntsen, Lina Gansmoe; Bergqvist, Göran; Davey, Marie Louise & Grøntvedt, Carl Andreas [Show all 13 contributors for this article] (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. Full text in Research Archive Show summary

  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

• Unsgård, Even; Meisingset, Erling L.; Rivrud, Inger Maren; Fossland, Gunn Randi; Thorvaldsen, Pål & Veiberg, Vebjørn [Show all 7 contributors for this article] (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. Full text in Research Archive Show summary

  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.

• 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. p. 1–12. doi: 10.1002/wlb3.01312. Full text in Research Archive Show summary

  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.

• 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. Full text in Research Archive Show summary

  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 [Show all 7 contributors for this article] (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. Full text in Research Archive Show summary

  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

• Mysterud, Atle; Solberg, Erling Johan; Meisingset, Erling L.; Panzacchi, Manuela; Rauset, Geir Rune & Strand, Olav [Show all 9 contributors for this article] (2023). Estimating and managing broad risk of chronic wasting disease spillover among cervid species. Ecosphere. 14(9), p. 1–17. doi: 10.1002/ecs2.4663. Full text in Research Archive Show summary

  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

• Mysterud, Atle; Langvatn, Rolf; Meisingset, Erling L. & Rivrud, Inger Maren (2022). Agricultural grasslands buffer density effects in red deer populations. Journal of Wildlife Management. ISSN 0022-541X. 87(3). doi: 10.1002/jwmg.22357. Full text in Research Archive Show summary

  Population densities of several cervid species have increased in recent decades in North America and Europe, and cervids frequently eat and damage agricultural crops. Competition and depletion of natural food resources are the main mechanisms for the density-dependent decline in vital rates of large herbivores. The extent to which access to agricultural crops can buffer density effects in cervid populations, however, is unknown. Agricultural grasslands cover more than a third of the European agricultural area, and red deer (Cervus elaphus) use these grasslands in many European countries. Over the past few decades, such grasslands have been subject to management intensification (with renewal and fertilization) in some areas and abandonment (no longer being harvested) in other areas. We used generalized linear mixed-effects models to examine the development of body masses of red deer in Norway during a period of population density increase in 16 local management units with different availability of cultivated grasslands (0.87–6.44%) in a region with active management of grasslands (Tingvoll, n = 5,780, 2000–2019) and a region with ongoing abandonment (Hitra, n = 10,598, 2007–2020). There was a consistent decline in the body mass of red deer linked to increased population density in both regions. A higher proportion of agricultural grassland was linked to higher body mass and lower density effects in both sexes and across all age classes. There is a link between body mass, survival, and reproduction. Therefore, the buffering of density effects of access to agricultural crops will fuel cervid population growth and lead to less natural regulation of abundance, making it more difficult to control dense cervid populations by harvesting.

• Mysterud, Atle; Skjelbostad, Isa Nergård; Rivrud, Inger Maren; Brekkum, Øystein & Meisingset, Erling L. (2021). Spatial clustering by red deer and its relevance for management of chronic wasting disease. Animals. 11(5), p. 1–13. doi: 10.3390/ani11051272. Full text in Research Archive Show summary

  Simple Summary Chronic Wasting Disease is a deadly infectious disease affecting cervids that was discovered in Norway in 2016. CWD can transmit through environmental reservoirs and aggregation and spatial clustering of animals may affect transmission. Deer usually forage on scattered forage, but anthropogenic food sources are often concentrated in space, leading to spatial aggregation. We determined what caused red deer to revisit the same locations in the environment, and the extent to which this was caused by anthropogenic food sources. We document that the most visited sites were indeed anthropogenic, which opens potential avenues to disease mitigation. Abstract Herbivores like cervids usually graze on widely scattered forage, but anthropogenic food sources may cause spatial revisitation and aggregation, posing a risk for transmission of infectious diseases. In 2016, chronic wasting disease (CWD) was first detected in Norway. A legal regulation to ban supplemental feeding of cervids and to fence stored hay bales was implemented to lower aggregation of cervids. Knowledge of further patterns and causes of spatial revisitation can inform disease management. We used a recently developed revisitation analysis on GPS-positions from 13 red deer (Cervus elaphus) to identify the pattern of spatial clustering, and we visited 185 spatial clusters during winter to identify the causes of clustering. Anthropogenic food sources were found in 11.9% of spatial clusters, which represented 31.0% of the clusters in agricultural fields. Dumping of silage and hay bales were the main anthropogenic food sources (apart from agricultural fields), and unfenced hay bales were available despite the regulation. The probability of the clusters being in agricultural fields was high during winter. It may be necessary to find other ways of disposing of silage and enforcing the requirement of fencing around hay bales to ensure compliance, in particular during winters with deep snow.

• Aikens, Ellen O.; Mysterud, Atle; Merkle, Jerod A.; Cagnacci, Francesca; Rivrud, Inger Maren & Hebblewhite, Mark [Show all 36 contributors for this article] (2020). Wave-like patterns of plant phenology determine ungulate movement tactics. Current Biology. ISSN 0960-9822. 30(17), p. 3444–3449. doi: 10.1016/j.cub.2020.06.032. Full text in Research Archive Show summary

  Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called ‘‘green-wave surfing’’ [3–5]. Yet general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested an emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of greenup facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n = 1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine-tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.

• Mysterud, Atle; Rivrud, Inger Maren; Gundersen, Vegard; Rolandsen, Christer Moe & Viljugrein, Hildegunn (2020). The unique spatial ecology of human hunters. Nature Human Behaviour. 4, p. 694–701. doi: 10.1038/s41562-020-0836-7. Full text in Research Archive Show summary

  Human hunters are described as ‘superpredators’ with a unique ecology. Chronic wasting disease among cervids and African swine fever among wild boar are emerging wildlife diseases in Europe, with huge economic and cultural repercussions. Understanding hunter movements at broad scales has implications for how to control the spread of these diseases. Here we show, based on analysis of the settlement patterns and movements of hunters of reindeer (n = 9,685), red deer (n = 47,845), moose (n = 60,365) and roe deer (n = 42,530) from across Norway (2001–2017), that hunter density was more closely linked to human density than prey density and that hunters were largely migratory, aggregated with increasing regional prey densities and often used dogs. Hunter movements extended across Europe and to other continents. Our results provide extensive evidence that the broad-scale movements and residency patterns of postindustrial hunters relative to their prey differ from those of large carnivores.

• Mysterud, Atle; Rauset, Geir Rune; Moorter, Bram Van; Andersen, Roy; Strand, Olav & Rivrud, Inger Maren (2020). The last moves: The effect of hunting and culling on the risk of disease spread from a population of reindeer. Journal of Applied Ecology. ISSN 0021-8901. 57, p. 2509–2518. doi: 10.1111/1365-2664.13761. Full text in Research Archive Show summary

  1. Hunting and culling are frequently used to combat infectious wildlife diseases. The aim is to markedly lower population density in order to limit disease transmission or to eradicate the host. Massive host culling can yield a trade-off when combating wildlife disease; it follows that intrusive actions may have unintended behavioural side effects, leading to the geographic spread of disease. The manner in which such excessive hunting and culling of hosts can affect the movement and dispersion of cervids has not been studied. 2. In this study, we quantified the behaviour (daily movements and habitat use) and dispersion of GPS-marked reindeer (n = 24) before and during the eradication of an entire population (>2,000 reindeer) infected with chronic wasting disease (CWD) in Norway. We compared behaviour and dispersion during 10 ordinary hunting seasons (2007–2016), an extended hunting season (2017) and marksmen culling (2017/2018). 3. Seasonality had a major impact on movements. Reindeer movements during the early hunting season (20 August–20 September) did not increase the overall movements compared to that in the pre-hunt season (20 July–19 August), while extended hunting into October (as in 2017) and marksmen culling from November to February markedly increased daytime movements relative to that normally observed in this time of the year. Towards the end of the eradication, the remaining reindeer sought refuge at restricted high-elevation areas with limited forage production. Reindeer used novel areas towards the perimeter of the range, but active herding during culling stopped one herd from leaving the CWD zone. 4. Synthesis and applications. With emerging wildlife diseases, host culling is becoming a more frequently used tool for managers in Europe. Our study highlights the potential trade-off between combating disease transmission within a population and the risk of geographic spread. Such insight is important to design mitigation measures, such as perimeter fencing or herding, to avoid the risk of the geographic spread of disease in cases of severe and economically important wildlife diseases. cervids, chronic wasting disease, disease ecology, disease management, host culling, movement ecology, spatial organization, unintended side effects

• Debeffe, Lucie Isabelle; Rivrud, Inger Maren; Meisingset, Erling L. & Mysterud, Atle (2019). Sex-specific differences in spring and autumn migration in a northern large herbivore. Scientific Reports. 9, p. 1–11. doi: 10.1038/s41598-019-42639-3. Full text in Research Archive Show summary

  Ongoing global warming is now affecting migratory cycles in a large variety of taxa in seasonally variable environments. Disruption of migratory systems can cause population decline and affect ecosystem function across the globe. It is therefore urgent to understand the drivers of migration and how the different fitness limitations of the sexes affect migration, but studies seldom considered the full annual cycle. We analysed the annual migration cycle of 237 red deer (Cervus elaphus) in Norway and investigate how different seasonal limitations affected the variation in a suite of migration characteristics. We found fundamental differences in migration phenology between seasons, and migratory traits were much more variable in males. Spring migratory movements were characterized by longer distance roamed, lower speed, lasted longer, more frequent use of stopovers, timing was more synchronized and coincided with onset of plant growth, and with higher daily activity levels. Timing of autumn migration was more variable and not closely related to cease of plant growth. Our study emphasizes the benefits of studying the full annual cycle to gain further insight into the migration process, and how understanding the limitations of the full annual migration process of both sexes is critical for conservation purposes.

• Rivrud, Inger Maren; Frank, Shane; Bischof, Richard; Mysterud, Atle; Steyaert, Sam & Hertel, Anne Gabriela [Show all 10 contributors for this article] (2019). Heritability of head size in a hunted large carnivore, the brown bear (Ursus arctos). Evolutionary Applications. 12(6), p. 1124–1135. doi: 10.1111/eva.12786. Full text in Research Archive Show summary

  Wild animal populations experience selection pressures from both natural and anthropogenic sources. The availability of extensive pedigrees is increasing along with our ability to quantify the heritability and evolvability of phenotypic traits and thus the speed and potential for evolutionary change in wild populations. The environment may also affect gene expressions in individuals, which may in turn affect the potential of phenotypic traits to respond to selection. Knowledge about the relationship between the genetic and environmental components of phenotypic variation is particularly relevant, given ongoing anthropogenically driven global change. Using a quantitative genetic mixed model, we disentangled the genetic and environmental components of phenotypic variance in a large carnivore, the brown bear (Ursus arctos). We combined a pedigree covering ~1,500 individual bears over seven generations with location data from 413 bears, as well as data on bear density, habitat characteristics, and climatic conditions. We found a narrow‐sense heritability of 0.24 (95% CrI: 0.06–0.38) for brown bear head size, showing that the trait can respond to selection at a moderate speed. The environment contributed substantially to phenotypic variation, and we partitioned this into birth year (5.9%), nonadditive among‐individual genetic (15.0%), and residual (50.4%) environmental effects. Brown bear head circumference showed an evolvability of 0.2%, which can generate large changes in the trait mean over some hundreds of generations. Our study is among the first to quantify heritability of a trait in a hunted large carnivore population. Such knowledge about the degree to which species experiencing hunting can respond to selection is crucial for conservation and to make informed management decisions. We show that including important environmental variables when analyzing heritability is key to understanding the dynamics of the evolutionary potential of phenotypic traits.

• Rivrud, Inger Maren; Meisingset, Erling L.; Loe, Leif Egil & Mysterud, Atle (2019). Future suitability of habitat in a migratory ungulate under climate change. Proceedings of the Royal Society of London. Biological Sciences. ISSN 0962-8452. 286(1899). doi: 10.1098/rspb.2019.0442. Full text in Research Archive Show summary

  With climate change, the effect of global warming on snow cover is expected to cause range expansion and enhance habitat suitability for species at their northern distribution limits. However, how this depends on landscape topography and sex in size-dimorphic species remains uncertain, and is further complicated for migratory animals following climate-driven seasonal resource fluctuations across vast landscapes. Using 11 years of data from a partially migratory ungulate at their northern distribution ranges, the red deer (Cervus elaphus), we predicted sex-specific summer and winter habitat suitability in diverse landscapes under medium and severe global warming. We found large increases in future winter habitat suitability, resulting in expansion of winter ranges as currently unsuitable habitat became suitable. Even moderate warming decreased snow cover substantially, with no suitability difference between warming scenarios. Winter ranges will hence not expand linearly with warming, even for species at their northern distribution limits. Although less pronounced than in winter, summer ranges also expanded and more so under severe warming. Summer habitat suitability was positively correlated with landscape topography and ranges expanded more for females than males. Our study highlights the complexity of predicting future habitat suitability for conservation and management of size-dimorphic, migratory species under global warming.

• Meisingset, Erling L.; Loe, Leif Egil; Brekkum, Øystein; Bischof, Richard; Rivrud, Inger Maren & Lande, Unni Støbet [Show all 9 contributors for this article] (2018). Spatial mismatch between management units and movement ecology of a partially migratory ungulate. Journal of Applied Ecology. ISSN 0021-8901. 55(2), p. 745–753. doi: 10.1111/1365-2664.13003. Full text in Research Archive Show summary

  1. Population-level management is difficult to achieve if wildlife routinely crosses administrative boundaries, as is particularly frequent for migratory populations. However, the degree of mismatch between management units and scales at which ecological processes operate has rarely been quantified. Such insight is vital for delimiting functional population units of partially migratory species common in northern forest ecosystems. 2. We combined an extensive dataset of 412 GPS-marked red deer (Cervus elaphus) across Norway with information on the size and borders of two administrative levels, the governmental level (municipality) and landowner level (local management units, LMUs), to determine the timing and scale of mismatch between animal space use and management units. We analysed how landscape characteristics affected the use of management units and the timing and likelihood of crossing borders between them, in an effort to delineate more appropriate units in various landscapes. 3. Median municipality size could potentially cover 70% of female and 62% of male annual ranges, while only 12% and 4% of LMUs were expansive enough to accommodate migratory routes in females and males, respectively. Red deer migrate along elevational gradients and are more likely to find both suitable lowland winter habitat and higher summer habitat within management units with variable topography. Consistent with this, the likelihood of border crossing decreased with increasing diversity of elevations. 4. Synthesis and applications. We demonstrate a considerable mismatch between animal space use and management units. Far-ranging movements and frequent administrative border crossings during autumn migration coincides with the period of active management (hunting season). Our study also highlights that, due to extensive movements of males, coordination of management aims may provide a more realistic avenue than increasing sizes of local management units. A more general insight is that the degree of mismatch between range use and management units depends on the season and landscape type. This needs to be accounted for when delimitating functional population units of migratory populations.

• Rivrud, Inger Maren; Sivertsen, Therese Ramberg; Mysterud, Atle; Åhman, Birgitta; Støen, Ole-Gunnar & Skarin, Anna (2018). Reindeer green-wave surfing constrained by predators. Ecosphere. 9(5). doi: 10.1002/ecs2.2210. Full text in Research Archive Show summary

  Migratory large herbivores in seasonal environments are known to follow the onset of new growth during spring, so‐called green‐wave surfing. This ensures prolonged access to forage with an optimal balance between forage quality and quantity. Many studies have focused on herbivores’ ability to follow the spring flush, but without considering potential constraints to surfing the green wave. The presence of predators is likely to be such a limitation, which could force herbivores to deviate from the optimal movement patterns in terms of forage access. We compared how well 319 reindeer (Rangifer tarandus) from seven different populations followed the green‐up at different population densities of brown bear (Ursus arctos). We found that reindeer at higher bear densities selected movement paths with lower access to high‐quality forage and deviated more in time from following the peak of the green wave, thus missing out on valuable forage. In addition, reindeer generally moved faster at higher bear densities, but this pattern was more consistent in forest habitats. Our results indicate that reindeer are forced to deviate from following the spring flush and alter their movement pattern in areas with high bear densities, which may lead to reduced body condition for reindeer experiencing high predation risk. With the recent recolonization of large carnivores in northern ecosystems, it is critical to understand the direct and indirect effects of predators on large herbivores in order to assess effects on population dynamics and potentially cascading consequences on ecosystem function.

• Bischof, Richard; Bonenfant, Christophe; Rivrud, Inger Maren; Zedrosser, Andreas; Friebe, Andrea & Coulson, Tim [Show all 8 contributors for this article] (2018). Regulated hunting re-shapes the life history of brown bears. Nature Ecology and Evolution. 2(1), p. 116–123. doi: 10.1038/s41559-017-0400-7. Full text in Research Archive Show summary

  Management of large carnivores is among the most controversial topics in natural resource administration. Regulated hunting is a centrepiece of many carnivore management programmes and, although a number of hunting effects on population dynamics, body-size distributions and life history in other wildlife have been observed, its effects on life history and demography of large carnivores remain poorly documented. We report results from a 30-year study of brown bears (Ursus arctos) analysed using an integrated hierarchical approach. Our study revealed that regulated hunting has severely disrupted the interplay between age-specific survival and environmental factors, altered the consequences of reproductive strategies, and changed reproductive values and life expectancy in a population of the world’s largest terrestrial carnivore. Protection and sustainable management have led to numerical recovery of several populations of large carnivores, but managers and policymakers should be aware of the extent to which regulated hunting may be influencing vital rates, thereby reshaping the life history of apex predators.

• Mysterud, Atle; Vike, Brit Karen; Meisingset, Erling L. & Rivrud, Inger Maren (2017). The role of landscape characteristics for forage maturation and nutritional benefits of migration in red deer. Ecology and Evolution. 7(12), p. 4448–4455. doi: 10.1002/ece3.3006. Full text in Research Archive Show summary

  Large herbivores gain nutritional benefits from following the sequential flush of newly emergent, high- quality forage along environmental gradients in the landscape, termed green wave surfing. Which landscape characteristics underlie the environmental gradi-ent causing the green wave and to what extent landscape characteristics alone explain individual variation in nutritional benefits remain unresolved questions. Here, we com-bine GPS data from 346 red deer (Cervus elaphus) from four partially migratory popula-tions in Norway with the satellite- derived normalized difference vegetation index (NDVI), an index of plant phenology. We quantify whether migratory deer had access to higher quality forage than resident deer, how landscape characteristics within sum-mer home ranges affected nutritional benefits, and whether differences in landscape characteristics could explain differences in nutritional gain between migratory and resident deer. We found that migratory red deer gained access to higher quality forage than resident deer but that this difference persisted even after controlling for land-scape characteristics within the summer home ranges. There was a positive effect of elevation on access to high- quality forage, but only for migratory deer. We discuss how the landscape an ungulate inhabits may determine its responses to plant phenol-ogy and also highlight how individual behavior may influence nutritional gain beyond the effect of landscape.

• Debeffe, Lucie Isabelle; Rivrud, Inger Maren; Brekkum, Øystein; Meisingset, Erling L. & Mysterud, Atle (2017). Implications of the forage maturation hypothesis for activity of partially migratory male and female deer. Ecosphere. 8(12), p. 1–16. doi: 10.1002/ecs2.2050. Full text in Research Archive Show summary

  Partial migration is common in a large variety of taxa in seasonally variable environments. Understanding the mechanisms underlying migration is important, as migration affects individual fi tness. Migratory herbivores bene fi t from delayed forage maturation and hence higher food quality during migra- tion and at their summer range, termed the forage maturation hypothesis (FMH). The link between diet quality and rumination time allows migrants eating a higher quality diet to spend less time on rumination, and they can thus allocate more time to additional feeding. However, such an argument implicitly assumes that deer are energy maximizers, while studies have reported also time minimization strategies under risk of predation. Male and female distributions are limited by different factors linked to both body size differ- ences and reproductive strategies, but there is no study investigating differences in activity pattern accord- ing to the individual migratory patterns for male and female deer. We here unify the FMH with the hypotheses predicting sex-speci fi c time allocation strategies. To test predictions of sex-speci fi c activity of resident and migratory red deer ( Cervus elaphus ), we analyzed activity data of 286 individuals that were fi tted with GPS collars from a population in western Norway. While migrants were more active during the migration itself, we found no differences in activity pattern between migrant and resident deer during the main growth season, neither in terms of proportion of daily time active nor in terms of daily mean movement speed, thus rejecting that deer were energy maximizers. Overall, we found that females were more active during the main growth season even after controlling for body size differences. These patterns are consistent with patterns predicted from sexual segregation theory linked to the reproductive strategy hypothesis. Our study highlights how the understanding of migration can be advanced by considering it in the context of different reproductive strategies of males and females.

• Loe, Leif Egil; Rivrud, Inger Maren; Meisingset, Erling L.; Bøe, Silje; Hamnes, Martine & Veiberg, Vebjørn [Show all 7 contributors for this article] (2016). Timing of the hunting season as a tool to redistribute harvest of migratory deer across the landscape. European Journal of Wildlife Research. ISSN 1612-4642. 62(3), p. 315–323. doi: 10.1007/s10344-016-1004-2. Full text in Research Archive
• Diekert, Florian Klaus; Richter, Andries Peter; Rivrud, Inger Maren & Mysterud, Atle (2016). How constraints affect the hunter's decision to shoot a deer. Proceedings of the National Academy of Sciences of the United States of America (PNAS). ISSN 0027-8424. 113(50), p. 14450–14455. doi: 10.1073/pnas.1607685113. Full text in Research Archive
• Rivrud, Inger Maren; Bischof, Richard; Meisingset, Erling L.; Zimmermann, Barbara; Loe, Leif Egil & Mysterud, Atle (2016). Leave before it's too late: Anthropogenic and environmental triggers of autumn migration in a hunted ungulate population. Ecology. ISSN 0012-9658. 97(4), p. 1058–1068. doi: 10.1890/15-1191.1. Full text in Research Archive

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• Bernardi, Cecilia Di; Tallian, Aimee Grace; Hansen, Jenny; Rivrud, Inger Maren; Mattisson, Jenny & Thorsen, Neri Horntvedt [Show all 11 contributors for this article] (2026). The sweet spots of risky mountains – individual variation in brown bear spring forays to reindeer calving grounds. Full text in Research Archive
• Panzacchi, Manuela; Moorter, Bram Van; Stange, Erik; Simensen, Trond; Sydenham, Markus A. K. & Thorsen, Neri Horntvedt [Show all 13 contributors for this article] (2026). GreenPlan - Lansering av ny kartportal for Grønn Infrastruktur i Norge og samutvikling av støtteverktøy for arealprioritering, scenario- og konsekvensvurderinger. DEL1 - STATUS HJORT. Full text in Research Archive
• 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. Full text in Research Archive
• Odden, John; Støen, Ole-Gunnar; Mattisson, Jenny; Thorsen, Neri Horntvedt & Rivrud, Inger Maren (2025). Forskning på gaupe og jerv i Rovviltregion 3. Full text in Research Archive
• Mysterud, Atle; Rivrud, Inger Maren & Meisingset, Erling L. (2025). Hva betyr innmarka for hjorten, og hjorten for innmarka? Hjorteviltet. ISSN 1502-3729. Full text in Research Archive
• Dæhlen, Marte & Rivrud, Inger Maren (2025). Eivind Lurås jakter på villsvin, som staten vil. Men de kan være bra for livet i skogen. [Internet]. Forskning.no. Full text in Research Archive
• Værvågen, Dag Holterud & Rivrud, Inger Maren (2025). Advarer bilister - elgen liker veisaltet. [Journal]. Romerikes Blad. Full text in Research Archive
• Rivrud, Inger Maren & Fremstad, Jørn (2025). Forskerne er svært forsiktige når de teller villsvin-unger. [Internet]. Forskning.no. Full text in Research Archive
• Rivrud, Inger Maren; Mattisson, Jenny; Thorsen, Neri Horntvedt & Odden, John (2025). Betydning av tetthet og felling av jerv på tap av sau. Full text in Research Archive
• Unsgård, Even; Meisingset, Erling L.; Rivrud, Inger Maren; Fossland, Gunn Randi; Thorvaldsen, Pål & Veiberg, Vebjørn [Show all 7 contributors for this article] (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. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Rolandsen, Christer Moe & Thorsen, Neri Horntvedt (2024). Villsvin: Bestandsovervåking av villsvin. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Støen, Ole-Gunnar; Tvete, Karl Ove & Rolandsen, Christer Moe [Show all 8 contributors for this article] (2024). Villsvinovervåking i Norge: Utbredelse og områdebruk. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Støen, Ole-Gunnar; Tvete, Karl Ove & Rolandsen, Christer Moe [Show all 8 contributors for this article] (2024). Villsvinovervåking i Norge: Utbredelse og områdebruk. Full text in Research Archive
• Rivrud, Inger Maren & Odden, John (2024). Raffinering av dyreforsøk ved NINA - villsvin og gaupe som eksempel. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Støen, Ole-Gunnar; Rolandsen, Christer Moe & Kindberg, Jonas [Show all 7 contributors for this article] (2024). Villsvin – merkeprosjekt og overvåking. Full text in Research Archive
• Rivrud, Inger Maren & Odden, John (2024). Villsvinovervåking i Norge: Kameraovervåking, områdebruk, genetikk og diett. Full text in Research Archive
• Rivrud, Inger Maren; Mattisson, Jenny; Thorsen, Neri Horntvedt & Odden, John (2024). Effekten av tetthet og uttak av jerv på rapporterte sauetap. Full text in Research Archive
• Haug, Erlend Johan Solvang & Rivrud, Inger Maren (2024). I dette området har ein aldri registrert villsvin før - så dukka fire villsvin opp. [Journal]. NRK Innlandet. Full text in Research Archive
• Størbu, Martin Kynningsrud & Rivrud, Inger Maren (2024). Ikke la elgen slikke bilen. [Journal]. Dagbladet. Full text in Research Archive
• Lange, Fredrik Ranheim & Rivrud, Inger Maren (2024). Forskning: Hiuttak av jerv har større effekt enn lisensjakt. [Journal]. Nationen. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John & Thorsen, Neri Horntvedt (2024). Villsvin – merkeprosjekt og overvåking. Full text in Research Archive
• Rosvold, Jørgen; Rolandsen, Christer Moe & Rivrud, Inger Maren (2024). Hva forteller kosten om villsvinet? [Internet]. Hjorteviltportalen. Full text in Research Archive
• Rolandsen, Christer Moe; Rosvold, Jørgen & Rivrud, Inger Maren (2024). Villsvin liker å rote i jorda etter trøfler. Har arten et kosthold som gjør at den slår rot i Norge? [Journal]. Nationen. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe; Støen, Ole-Gunnar & Davey, Marie Louise [Show all 12 contributors for this article] (2023). Villsvin: Bestandsovervåking, GPS-merking og genetikk. Full text in Research Archive
• Odden, John & Rivrud, Inger Maren (2023). Kan jervtetthet forklare tap av sau? Full text in Research Archive
• Landrø, Juliet; Rivrud, Inger Maren & Rosvold, Jørgen (2023). Podcast Naturligvis: Villsvin - hva gjør de i Norge? [Internet]. NINA. Full text in Research Archive
• Sandbu, Anders & Rivrud, Inger Maren (2023). NINA-forsker spår lang dags ferd mot villsvinutrydding. [Journal]. Bondebladet. Full text in Research Archive
• Günther, Julie Helene & Rivrud, Inger Maren (2023). Utbrudd av afrikansk svinepest: - Vi har aldri opplevd å ha sykdommen så tett på Norge. [Journal]. NRK Oslo og Viken. Full text in Research Archive
• Nagy, Petter & Rivrud, Inger Maren (2023). Overvåkning gir god kunnskap om svina. [Journal]. Jakt. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John & Thorsen, Neri Horntvedt (2023). Villsvin – merkeprosjekt og overvåking. Full text in Research Archive
• Rivrud, Inger Maren (2023). Villsvin i Norge GPS-merket for første gang. [Radio]. NRK P1 Østfold. Full text in Research Archive
• Rivrud, Inger Maren; Odden, John; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe; Støen, Ole-Gunnar & Kindberg, Jonas [Show all 7 contributors for this article] (2023). Villsvin i Norge – overvåking og merkeprosjekt. Full text in Research Archive
• Nouri, Samar & Rivrud, Inger Maren (2023). Det var litt skummelt. Dette møtte Katja på vei til jobb. [Journal]. Romerikes Blad. Full text in Research Archive
• Andersrød, Benjamin Vorland; Günther, Julie Helene & Rivrud, Inger Maren (2023). Villsvin GPS-merket i Noreg for første gong. [Journal]. NRK Oslo og Viken. Full text in Research Archive
• Røyne, Henrik Hokaasen & Rivrud, Inger Maren (2023). Frykter invasjon av «supergriser». [Journal]. TV2. Full text in Research Archive
• Rivrud, Inger Maren (2022). Oppstart av fangst og merking av villsvin. [Radio]. NRK P1 Østfold. Full text in Research Archive
• Svendsen, Marthe & Rivrud, Inger Maren (2022). Aggressiv elg på Brundalen jaget ansatt i Viltpatruljen. [Journal]. NRK Trøndelag. Full text in Research Archive
• Nygaard, Louise & Rivrud, Inger Maren (2022). Ble overrasket med elg-vask på vei til jobb. [Journal]. Budstikka. Full text in Research Archive
• Rivrud, Inger Maren & Odden, John (2022). Villsvin – en ny art på Østland. Full text in Research Archive
• Rivrud, Inger Maren; Rolandsen, Christer Moe; Rauset, Geir Rune; Kvasnes, Mikkel Andreas Jørnsøn; Mysterud, Atle & Solberg, Erling Johan (2021). Hjorteviltpåkjørsler i Norge – Årsaksforhold, lokalisering, risiko og datakvalitet. Full text in Research Archive
• Rolandsen, Christer Moe; Odden, John; Thorsen, Neri Horntvedt & Rivrud, Inger Maren (2020). Overvåking av villsvinbestanden i Norge. Full text in Research Archive
• Odden, John; Rosvold, Jørgen; Rolandsen, Christer Moe & Rivrud, Inger Maren (2020). Villsvin i Norge - hva nå? p. 42–42. Full text in Research Archive
• Meisingset, Erling L. & Rivrud, Inger Maren (2019). Hjortens tilgang på sommer- og vinterbeite under fremtidige klimaendringer. Full text in Research Archive
• Rivrud, Inger Maren; Loe, Leif Egil; Meisingset, Erling L. & Mysterud, Atle (2019). Hjortens tilgang på sommer- og vinterbeite under fremtidige klimaendringer. Full text in Research Archive
• Rivrud, Inger Maren (2018). Hva påvirker jegernes avgjørelse om å skyte – eller ikke skyte? Full text in Research Archive
• Rivrud, Inger Maren; Loe, Leif Egil; Meisingset, Erling L. & Mysterud, Atle (2018). Hjortens tilgang på sommer- og vinterbeite under fremtidige klimaendringer. Full text in Research Archive
• Rivrud, Inger Maren (2017). Factors affecting seasonal migration in ungulates. Full text in Research Archive
• Rivrud, Inger Maren (2016). Heritability of body size in a wild mammal: The brown bear (Ursus arctos). Full text in Research Archive
• Støen, Ole-Gunnar; Rivrud, Inger Maren; Nilsen, Erlend Birkeland; Andersson, Peter & Jonsson, Benny (2025). Forvaltning av bjørn i reinkalvingsområder i Sverige: Områdestørrelser og bestandsnivå. Norsk institutt for naturforskning (NINA). ISSN 9788242655486. Full text in Research Archive Show summary

  I denne rapporten undersøkte vi hvilken størrelse på forvaltningsområder rundt reinkalvingsområdene som kan være hensiktsmessig for en arealbasert forvaltning av brunbjørn i Sverige, samt hvilke effekter ulike uttak av bjørn i disse områdene kan ha på bjørnebestanden. Slik kunnskap er avgjørende for å sikre en bærekraftig bjørneforvaltning innenfor de fastsatte toleransenivåene for reindriften. Tidligere studier har vist at bjørn kan stå for en betydelig del av reintapet, særlig i kalvingsperioden. Analysene våre bygger på GPS- og drapstaktdata fra to studier i Sverige: Norrbotten (2010–2012) og Dalarna (2019–2024). Vi estimerte buffersoner rundt kalvingsområdene separat for kjønn ved hjelp av to tilnærminger: (1) leveområdeoverlapp kombinert med leveområdestørrelse og (2) modellert posisjonsavstand fra kalvingsområdets grense som funksjon av antall kalv tatt. Basert på leveområdeoverlapp beregnet vi en hunnbjørnbuffer på om lag 10 km og en hannbjørnbuffer på om lag 28 km (95-persentil). Vår vurdering var at en buffersone på 10 km ga den mest hensiktsmessige avgrensningen av forvaltningsområder, ettersom denne i stor grad omfattet bjørner av begge kjønn som bidro mest til reintapet. Hannbjørnbufferen kan fungere som et supplement for å anslå hvilken andel av hannbjørnbestanden som kan påvirke tapene. Buffersoner basert på posisjonsavstandsmetoden ga mindre buffersoner, men ble vurdert som mindre egnet på grunn av stor variasjon og lavere treffsikkerhet. Ved å kombinere buffersoner, tetthetsestimater og individuelle drapstakter utarbeidet vi en bestandsmatrise og gjennomførte risikosimuleringer for vinterflokkstørrelser på 2 500 og 7 500 rein. Resultatene viste at for en vinterflokk på 2 500 rein kunne om lag 20 bjørner (10 hunner og 10 hanner) innenfor forvaltningsområdet være forenlig med mindre enn 10 % tap, mens rundt 10 bjørner (5 hunner og 5 hanner) tilsvarte mindre enn 5 % tap. For vinterflokker på 7 500 rein var tilsvarende bestandsnivåer om lag tre ganger høyere. Når vi stilte krav om høy sikkerhet (90 %) for ikke å overskride toleransenivåene, viste simuleringene at antallet bjørner måtte reduseres ytterligere, til om lag 16 og 6 bjørner ved henholdsvis 10 % og 5 % tap for en vinterflokk på 2 500 rein. Usikkerheten i simuleringene er størst ved lave bestandsnivåer, som en forventet effekt av tilfeldige variasjoner. Vi benyttet også en aldersstrukturert populasjonsmodell for bjørn til å beregne årlige avskytingsnivåer som kunne holde bestandene stabile. Den årlige vekstraten i en bestand uten jakt ble beregnet til rundt 12 %. Avskytingen var relativt lav i absolutte tall når bjørnebestanden allerede lå innenfor toleransenivåene på 5 % og 10 % tap, for eksempel rundt én bjørn per år eller annethvert år ved en bestand på om lag 6 bjørner, og rundt to bjørner per år ved en bestand på om lag 16 bjørner i et område med 2 500 rein. Når vi skalerte beregningene opp til nasjonalt nivå, med en samlet vinterflokk på om lag 230 000 rein, viste analysene at et toleransenivå på 5 % tap med lav risiko for overskridelse tilsvarte rundt 1 000 bjørner i og rundt kalvingsområdene. Dette tilsvarer om lag en tredjedel av det nasjonale bestandsestimatet i Sverige i 2022. Det samlede arealet av kalvingsområder med tilhørende 10 km buffersone utgjorde tilsvarende om lag en tredjedel av arealet i län med målsetting om bjørnebestand. Lisensjakt framsto som et sentralt virkemiddel for å regulere antallet bjørner som bidrar til tap av rein, ettersom bjørner med leveområder i eller nær kalvingsområdene i stor grad benyttet de samme områdene fram til høsten. Praktisk gjennomføring kan imidlertid være krevende, og skadefelling i vårperioden vil derfor fortsatt være et nødvendig supplement. Avslutningsvis understreker vi at en effektiv arealbasert forvaltning forutsetter gode data om bjørnetetthet og bestandsstørrelse, reinens faktiske arealbruk, samt samlet predasjon fra flere rovdyrarter, ettersom toleransenivåene gjelder samlet tap og ikke bjørn alene.

• Thorsen, Neri Horntvedt; Bahlk, Sunniva Helene; Rolandsen, Christer Moe; Rivrud, Inger Maren & Odden, John (2025). Bestandsovervåking av villsvin. Status 2025. Norsk institutt for naturforskning (NINA). ISSN 9788242654915. Full text in Research Archive Show summary

  Thorsen, N.H., Bahlk, S., Rolandsen, C.M., Rivrud, I.M. & Odden, J. 2025. Bestandsovervåking av villsvin. Status 2025. NINA Rapport 2666. Norsk institutt for naturforskning. Villsvinet regnes som en fremmed art i Norge, og forvaltningen har som målsetting å utrydde arten i Norge. Arten er omdiskutert; den verdsettes som jaktressurs, men vekker bekymring på grunn av risiko for sykdomsoverføring og skader på jordbruksarealer. God kunnskap om artens utbredelse og bestandsutvikling er derfor viktig for en kunnskapsbasert forvaltning. Norsk institutt for naturforskning (NINA) har siden 2019 overvåket villsvinbestanden i Norge. I denne rapporten presenteres oppdaterte resultater for 2025. Data fra et nettverk av kamerafeller (SCANDCAM), Artsobservasjoner, fallvilt og rapporterte jaktdata ble brukt til å kartlegge artens utbredelse. Bestandsutvikling overvåkes ved hjelp av jaktdata og data fra kamerafeller, mens bestandstetthet ble beregnet for Halden og Aremark ved hjelp av en «Random Encounter Model» (REM) basert på tilfeldig plasserte kamerafeller. Utbredelsen av villsvin i Norge er relativt stabil, og hovedutbredelsen er fortsatt i Halden og Are-mark, med sporadiske observasjoner i Østfold, Akershus og Innlandet. I jaktåret 2024/2025 ble 334 av totalt 380 felte villsvin rapportert fra Halden og Aremark. Tettheten i dette området ble estimert til 0,47 individer per km² (95 % KI: 0,20–0,89), tilsvarende om lag 448 individer. Dette er på nivå med tidligere år, og tyder på en stabil bestand i perioden 2020–2025. Til tross for høy jaktinnsats har bestanden holdt seg stabil, noe som indikerer høy rekruttering og/eller innvandring fra Sverige. Det er store usikkerhetsmarginer knyttet til tetthetsestimatene, og resultatene må tolkes med forsiktighet. Samlet sett tyder dataene på at forvaltningen har lykkes i å begrense videre spredning av arten, men fortsatt overvåking er nødvendig for å kunne oppdage eventuelle endringer raskt, særlig med tanke på risikoen for afrikansk svinepest og andre sykdommer.

• 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. Full text in Research Archive Show summary

  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.

• Didriksen, Regine Marie; Støen, Ole-Gunnar; Rivrud, Inger Maren & Gundersen, Vegard (2025). The Impact of Anthropogenic Disturbance on the Interaction Between Brown Bears (Ursus arctos) And Semi-Domesticated Reindeer (Rangifer tarandus) During The Calving Period in Mountainous Habitat. Norges miljø- og biovitenskapelige universitet (NMBU). Full text in Research Archive Show summary

  Human recreational activity in natural landscapes has increased in the past decades. Combined with other land-use interests, this has placed significant pressure and disturbances on natural areas, along with impacts on ecosystems and interactions between species. Semi-domesticated reindeer (Rangifer tarandus) are a vital part of Sámi culture and livelihoods, and are especially sensitive to human disturbance during the calving period. In some areas can predators such as brown bears (Ursus arctos) cause economic losses to owners by preying on their livestock. This study aimed to assess whether human recreational activity in mountain calving grounds affects the habitat selection of brown bears and semi-domesticated reindeer during the calving period, and whether this in turn influences brown bear predation patterns. Data utilized in this study included GPS-data from brown bears and semi-domesticated reindeer, carcass locations from reindeer killed by GPS-collared bears and human activity data. Both species’ habitat selection was modelled through Resource Selection Functions (RSFs) with a use-availability design. The final model was used to develop habitat suitability and co-occurrence maps, which helped to identify suitable areas for each species and visualize where carcasses have been found. Results showed that human recreational activity influenced both brown bears and semi-domesticated reindeer habitat selection, but at varying degrees. Brown bears consistently avoided areas with high human activity, while reindeer exhibited avoidance mainly in the early part of the calving period. Brown bears entered the mountain mostly during the night to predate on semi-domesticated reindeer, when human activity was low. Certain trails in the study area were more used by humans than others, offering guidance for visitor management. Human activity did not appear to influence brown bear predation patterns and may even act as a deterrent to bears if strategically managed. This study highlights how human recreational activity affects the habitat selection of both species. Understanding these dynamics is crucial for future natural resource and visitor management, especially as human pressure on natural areas continues to grow. With informed management, a better coexistence between outdoor recreationists, wildlife and local livelihoods can be achieved.

• 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. Full text in Research Archive Show summary

  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.

• Odden, John; Thorsen, Neri Horntvedt; Mattisson, Jenny; Rivrud, Inger Maren; Tvete, Karl Ove & Støen, Ole-Gunnar [Show all 7 contributors for this article] (2025). Scandlynx. Statusrapport 2023-2024. Norsk institutt for naturforskning (NINA). ISSN 9788242653970. Full text in Research Archive Show summary

  Forskningsprosjektet Scandlynx studerte gauper fra midten av 1990-tallet fram til 2016 med ulike typer VHF- eller GPS-sendere. Etter en pause på noen år fikk vi i 2023 midler gjennom Miljødirektoratets system for finansiering av løpende FoU-aktivitet knyttet til forvaltningens kunnskapsbehov på rovviltfeltet. Denne rapporten presenterer resultatene fra de første to årene med basisfinansiering. I tillegg har prosjektet mottatt støtte fra Statsforvalteren i Innlandet samt Statsforvalteren i Østfold, Buskerud, Oslo og Akershus. I Norge reguleres gaupebestanden gjennom årlig kvotejakt, med mål om å holde den stabil innenfor fastsatte bestandsmål i de ulike forvaltningsregionene. Likevel har bestanden i enkelte regioner ikke økt som forventet uten kvotejakt. En bærekraftig forvaltning av gaupe krever økt forståelse av de mekanismene som styrer bestandsutviklingen. En mulig forklaring er hvordan landskapsendringer påvirker gaupas spredning og rekolonisering. Siden 2023 har prosjektet derfor hatt som mål å kartlegge landskapets permeabilitet – altså hvor tilgjengelig det er for gaupe – og identifisere mulige spredningskorridorer i områder med høy infrastruktur. I tillegg har vi studert gaupas predasjonsmønstre, overlevelse og reproduksjon. Data fra GPS-merkede hunngauper med unger vil også bidra til å evaluere overvåkingssystemet. For å undersøke disse forholdene har vi utstyrt 19 gauper med GPS-sendere i Sørøst-Norge siden 2023. Fire voksne hunngauper i fylkene rundt Oslo har beveget seg over arealer fra 183 km² til 248 km² i løpet av studieperioden (beregnet med 100 % MCP). Hanngaupene har hatt større områder, fra 458 km² til 1145 km². Så langt har vi fulgt fire familiegrupper gjennom hele eller deler av registreringssesongen, og samtlige har blitt fanget opp av overvåkingssystemet. Vi har gjennomført ni intensivperioder på åtte hanngauper i totalt 132 døgn der senderne har tatt en posisjon hvert tjuende minutt i hele perioden. Vi har gjennomført byttedyrundersøkelser og kontrollert alle klustre i disse periodene, og funnet 39 byttedyr drept av gaupene. Utenom intensivperiodene har gaupene tatt en posisjon annenhver time. Vi har sett etter byttedyr utenom de intensive periodene, og det har blitt lagt ned en betydelig innsats av lokale samarbeidspartnere og NINA personell. Totalt har vi besøkt 924 kluster og fulgt gaupene ekstensivt gjennom 1873 gaupedager. I disse periodene har vi registrert 417 byttedyr. Rådyr var det klart mest drepte byttedyret, men gaupene har også drept hjort, sau og småvilt.

• Støen, Ole-Gunnar; Thorsen, Neri Horntvedt; Andersson, Peter; Jönsson, Mattias; Segerström, Peter & Tveraa, Torkild [Show all 17 contributors for this article] (2025). Bjørnens predasjon på tamrein. Sluttrapport fra Bjørn- og tamreinprosjektet i Idre, Sverige. Norsk institutt for naturforskning (NINA). ISSN 9788242654038. Full text in Research Archive Show summary

  Brunbjørnen (Ursus arctos) er en betydelig predator på hjortedyr, særlig kalver. Studier fra Norrbotten, Sverige, viser at bjørnen kan forårsake store kalvetap i tamreinflokker. I Norge erstattes tap til rovvilt, og tap til bjørn er en vedvarende kilde til konflikt. Myndighetene har tidligere vurdert en mer risikobasert erstatningsmodell, der bjørnens drapstakt står sentralt. For å øke kunnskapen om tap til bjørn ble det gjennomført en studie i Idre sameby, Sveriges sydligste sameby. Målet var å kvantifisere bjørnens drapstakt i et reinbeitedistrikt med kalving på fjellet. Bjørner ble GPS-merket innenfor et 1 792 km² stort område rundt kalvingslandet i Idre. Siden drapstakten kan variere med byttedyrets kondisjon, ble data om reinens vekt, drektighet og kalveoverlevelse samlet inn. Bjørnene ble sporet med GPS, og ansamlinger av posisjoner (kluster) der bjørnen oppholdt seg i minst 10 minutter, ble undersøkt i felt. Totalt ble 33 bjørner GPS-merket, noe som resulterte i 9 719 klustre om våren (1. mai – 20. juni) og 6 063 om sommeren (21. juni – 20. september) og funn av 410 kadavre fra seks ulike bytte-dyrarter. Om våren i årene 2019–2024 oppholdt 16 av de 33 bjørnene seg blant kalvende rein i mer enn ett døgn, og i løpet av 480 dager tok disse 160 reinkalver og 15 voksne rein. Gjennomsnittlig antall rein tatt per bjørn om våren (1. mai – 20. juni) var 5,5 reinkalver og 0,52 voksne rein, med en daglig drapstakt på 0,31 reinkalver og 0,02 voksne rein. Drapstakten var høyere på fjellet (2,70 reinkalver per dag) enn i skogen (0,19 reinkalver per dag). Idre sameby har en lavere drapstakt enn skogssamebyene i Norrbotten om våren, fordi overlappet mellom bjørn og rein er mindre. Reinen i Idre oppholder seg 80 % av tiden på fjellet, mens bjørnene er der under 4 % av tiden. Likevel var 41 % av reinkalvene bjørnene tok på fjellet. Det var betydelig variasjon mellom individer og mellom år for samme individ. En statistisk modell som tok hensyn til denne variasjonen viste at en gjennomsnittlig bjørn tok 3,75 reinkalver i løpet av våren. DNA- og GPS-data fra 2022 antyder at opptil 36 bjørner kan ha vært i Idre-området, med et anslått tap på 58–127 reinkalver til bjørn som tilsvarer 16–36 % av tapene i Idre sameby før kalvemerking. Om sommeren tilbrakte 24 av de 33 GPS-merkede bjørnene til sammen 1 126 dager blant reinen, hvor de tok 21 reinkalver og 21 voksne rein. Drapstakten var da betydelig lavere – 0,02 reinkalver og 0,02 voksne rein per dag – bare 6,5 % av vårens nivå. Likevel blir flere rein tatt om sommeren i Idre enn i Norrbotten, trolig på grunn av reinens habitatbytte etter kalvemerking. Kalveproduksjonen i Idre er høy, og tapene fram til kalvemerking er større enn forventet i et område uten store rovdyr. Funnene viser at enkelte bjørner står for mye av kalvetapet, og at antall dager de tilbringer i kalvingsområdet er avgjørende for hvor mye rein de tar. Målrettet uttak av bjørn rettet mot kalvingsområder kan derfor være effektive forvaltningstiltak.

• Rivrud, Inger Maren; Odden, John; Davey, Marie Louise; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe & Støen, Ole-Gunnar [Show all 12 contributors for this article] (2024). Villsvin i Norge. Bestandsovervåking: Utbredelse, områdebruk og diett. Norsk institutt for naturforskning (NINA). ISSN 9788242652607. Full text in Research Archive Show summary

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

• Rivrud, Inger Maren; Mattisson, Jenny; Thorsen, Neri Horntvedt & Odden, John (2024). Betydning av tetthet og felling av jerv på tap av sau. Norsk institutt for naturforskning (NINA). ISSN 9788242652256. Full text in Research Archive Show summary

  Rivrud, I.M., Mattisson, J., Thorsen, N.H. & Odden, J. 2024. Betydning av tetthet og felling av jerv på tap av sau. NINA Rapport 2417. Norsk institutt for naturforskning. De siste 40 årene har vi hatt en vedvarende konflikt rundt forvaltningen av jerv, forårsaket av predasjon på sau og tamrein på utmarksbeite. Myndighetene har brukt store ressurser på å redusere predasjon på sau hovedsakelig gjennom bruk av lisensfelling og skadefelling. Det er viktig at effekten av tiltakene forankres i god faglig dokumentasjon på i hvilken grad de fungerer tapsreduserende. I denne rapporten analyserte vi forholdet mellom jervetetthet og tap av lam i Norge. I tillegg har vi sett på om uttak av jerv påvirker tap av sau i årene etter uttaket. Siden jerv i hovedsak tar lam, analyserte vi effekten av jerv og andre faktorer på tapet av lam i beitelagene. Vi benyttet tall på antall lam sluppet på beite og årlige tap av lam på beitelagsnivå fra Organisert beitebruk mellom 2014-2022. Jervetettheten i de ulike beitelagene ble hentet fra kart produsert av prosjektet RovQuant. Vi fant at tap av lam i beitelagene økte med økende jervetetthet. Jervetettheten i beitelagene varierte mellom 0-0,64 jerv pr 100 km2 i perioden. For hver 0,1 flere jerv pr 100 km2 på beitelagsnivå viste modellen en gjennomsnittlig økning i totaltap av lam på 4,3 dyr i løpet av sommeren. Videre økte lammetapet med økt antall jerv felt under skadefelling, der modellen predikerte et gjennomsnittlig økt tap på 2,9 lam per jerv felt under skadefelling i beitelaget. De predikerte tapstallene er gjort for et gjennomsnittlig beitelag i datasettet, der det slippes 1265 lam på beite, og i modellen korrigeres det for antall lam sluppet. Tetthet og skadefelling av jerv forklarte kun en liten del av variasjonen i totaltapene noe som peker på at det er mange andre faktorer som påvirker tap av lam uavhengig av jerv. Vi undersøkte effekt av uttak av jerv på endring i tapstall for lam mellom år ved å regne ut endringen pr beitelag fra et år (t) til det neste (t+1) og fra år t og to år frem (t+2). Modellene for endring i tap over både ett og to år viste at lammetapet avtok i beitelaget når jervetettheten ble redusert i perioden, med en predikert reduksjon på 4,5 lam tapt per 0,1 færre jerv pr 100 km2 i beitelaget over både ett og to år. Modellene viste også at hiuttak førte til en reduksjon av tapene med en predikert reduksjon i antall lam tapt i beitelagene året etter hiuttak på 27,5 dyr, sammenlignet med beitelag der det ikke var foretatt hiuttak. Vi fant også en fortsatt effekt av hiuttak på tapene etter to år, men kunne ikke skille på effekten mellom de to årene. Vi har dokumentert at tap av lam i beitelagene økte med økende jervetetthet, og at reduksjon i jervetetthet i beitelagene fører til redusert lammetap. Vi fant økt lammetap ved flere jerver felt under skadefelling, men ingen effekt av lisensfelling eller skadefelling på endring i de lokale totaltapene året etter eller to år etter uttak. Hiuttak av jerv er et kontroversielt virkemiddel. Vi fant her at hiuttak førte til lavere lammetap både ett og to år etter felling. Det var mye variasjon i dataene og stor usikkerhet i estimatene da det er mange andre faktorer som påvirker lammetap, så resultatene må tolkes med varsomhet. Vi fant ingen effekt av antall jerv felt i lisensjakt på lammetap. Det kan nok skyldes at jerv skutt i lisensjakta ikke nødvendigvis blir skutt i beiteområder med store tap og at nye jerver raskt tar over områdene til de skutte jervene. På stor skala vil lisensjakta regulere tettheten av jerv som igjen påvirker lammetapene. Dette studiet viser med all tydelighet at ytterligere kunnskap om mekanismene som styrer tap av sau til jerv vil kreve at vi følger GPS-merkede jerver i ulike beiteområder i Norge for å få gode tall på individuelle drapstakter og hvordan dette varierer. Det er også behov for å få ytterligere kunnskap om andre faktorer som påvirker tap av sau på utmarksbeite i tillegg til de store rovdyrene.

• König, Emilie; Mysterud, Atle; Rivrud, Inger Maren & Lindsø, Lars (2024). Using camera trapping to estimate small mammal occurrence. Universitetet i Oslo. Full text in Research Archive
• 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. Full text in Research Archive Show summary

  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. Full text in Research Archive Show summary

  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.

• Odden, John; Thorsen, Neri Horntvedt; Bahlk, Sunniva Helene; Rolandsen, Christer Moe; Rivrud, Inger Maren & Rosvold, Jørgen (2023). Bestandsovervåking av villsvin – Status 2022. Norsk institutt for naturforskning (NINA). ISSN 9788242650917. Full text in Research Archive Show summary

  NINA kartlegger utbredelsen og bestandsutvikling hos villsvin på oppdrag fra Miljødirektoratet. I denne rapporten presenterer vi tilgjengelig kunnskap om utbredelse og utvikling i antall villsvin i Norge, og ser på hvordan utviklingen i bestanden har vært siden 2021. I arbeidet med å kartlegge utbredelsen av villsvin i Norge benyttet vi observasjoner fra SCANDCAM sitt nettverk av kamerafeller, Artsobservasjoner, fallviltdata på villsvin i Hjorteviltregisteret, og lokaliteten til skutte villsvin rapportert til NINA og Veterinærinstituttet. Hovedutbredelsen av villsvin er langs svenskegrensa, fra Halden i sør til Elverum i nord, men enkeltindivider på spredning kan forventes å forekomme over store deler av Sør-Norge. Det observeres klart flest villsvin på kamerafellene i kommunene Halden og Aremark. I jaktåret 2021/2022 ble 79 % av alle felte villsvin skutt i disse to kommunene. Jaktstatistikken viser en nedgang i antall rapportert felte villsvin i både Innlandet og Viken. Det er første gang antall skutte villsvin har sunket siden 2014/15. Vi ser at frekvensen av villsvinobservasjoner på kamerafellene i Akershus/Østfold ser ut til å være stabil, mens det er en kraftig nedgang i antall observasjoner på kamerafellene i Innlandet. Samlet sett gir dataene et klart inntrykk av at villsvinbestanden i kjerneområdene i Aremark og Halden er stabil, men at det er en nedgang i Hedmark.

• 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. Full text in Research Archive Show summary

  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. Full text in Research Archive Show summary

  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.

• Odden, John; Thorsen, Neri Horntvedt; Rolandsen, Christer Moe; Rivrud, Inger Maren; Kindberg, Jonas & Rosvold, Jørgen (2022). Bestandsovervåking av villsvin. Status og forslag til overvåkingsmetodikk. Norsk institutt for naturforskning (NINA). ISSN 9788242648891. Full text in Research Archive Show summary

  Villsvin, Sus scrofa, Overvåking, Utbredelse, tetthet, Random encounter model, kamerafeller, SCANDCAM Norge

• Valle, Torgeir Holmgard; Odden, John; Mysterud, Atle; Thorsen, Neri Horntvedt & Rivrud, Inger Maren (2021). Flashing Large Mammals: Does white LED flashes in camera traps affect detection rates of target species? Universitetet i Oslo. Full text in Research Archive Show summary

  Camera trapping is an increasingly important tool in animal ecology that is generally targeted towards large mammals, and especially large carnivores. Nonetheless, the cameras are triggered by all large and medium-sized animal species in the area, and thus gathers valuable data on the whole ecological community, like their diel and seasonal activity patterns. White light flashes are sometimes utilized to get more detailed photos allowing for capture-recapture based population estimates for naturally marked species, like the Eurasian lynx (Lynx lynx). However, the white light could function as a stressor or attractant for different species, which would affect density estimates. There is evidence of behavioural change in several mammal species, when exposed to a white flash, but quantifications on the detection rate of species are still lacking. Therefore, I investigated whether introducing an additional white LED camera trap (CT) at established CT sites affected the detection rates of the most common wild mammal species in the area. As CT flashes only are used while ambient lighting is low, I quantified the species’ diel patterns in the process. I predicted that the detection rate of species with nocturnal and crepuscular activity patterns would be altered as a response to the white light stimuli, and that the extent of the effect would depend on the species’ visual acuity. The results showed no significant effects of white LED flashes, when compared to IR flashes, suggesting that white-flash cameras are suitable for studies using indices and capture-mark-recapture estimators.

• Støen, Ole-Gunnar; Thorsen, Neri Horntvedt; Nilsen, Erlend Birkeland; Rivrud, Inger Maren & Kindberg, Jonas (2021). Brunbjørnbinners arealbehov og betydningen av svensk forvaltning for bestandsutviklingen i Region 6. Norsk institutt for naturforskning (NINA). ISSN 9788242647306. Full text in Research Archive Show summary

  Trøndelag - Sverige - brown bear - brunbjørn - arealbruk - habitat - populasjonsutvikling - forvaltning- Ursus arctos - area use - habitat - population development - management

• Seeberg, Frida; Mysterud, Atle & Rivrud, Inger Maren (2021). Use of supplemental feeding sites by roe deer in a disease transmission context. Universitetet i Oslo. Full text in Research Archive
• Skjelbostad, Isa Nergård; Mysterud, Atle; Meisingset, Erling L. & Rivrud, Inger Maren (2020). Use of spatial clusters by red deer (Cervus elaphus) to identify transmission hot spots in a Chronic Wasting Disease context. Universitetet i Oslo. Full text in Research Archive Show summary

  Abstract In 2016 Chronic Wasting Disease was discovered in Nordfjella, Norway for the first time in a female reindeer (Rangifer tarandus). Since then Norwegian nature management have implemented several measures in the affected area in Nordfjella and its surrounding municipalities to stop the spread of the prion disease. The prions’ long viability in soil outside of a host body increases the risk of spillover to other cervid species. The risk is especially high for the red deer (Cervus elaphus) population of Lærdal being the densest population in the Nordfjella region, and with its overlapping summer ranges with the affected reindeer herd. Norwegian red deer have been studied for a long time and a lot is known about their broad scale habitat selection and seasonal migration patterns. However, little is known about when and why the red deer repeatedly use the same locations on a fine scale, which has become a more relevant topic now as it may facilitate disease transmission. With location data from 14 red deer in Lærdal from 2017 to 2019, and through field work in Lærdal, I have quantified the proportion of spatial clusters containing natural forage, supplemental forage aimed for cervids and supplemental forage not aimed for cervids. I have also been able to quantify the seasonal pattern of number of spatial clusters. I found that non-intentional feeding caused as much as 31% of the clustering in infield habitats, and that most of this was in the form of leftover silage dumped in fields. I found that non-intentional feeding facilitates the contact between cervid species, and that it therefore can facilitate the spillover of Chronic Wasting Disease from reindeer, through red deer, and to roe deer (Capreolus capreolus) or other cervid species that do not have overlapping ranges with reindeer. Aggregation in infield habitat and around non-intentional feeding was more frequent during periods with more snow. Lastly, I discovered during the field work that even though there is a requirement of fencing in hay bales to help minimize aggregation of cervids in Lærdal, there were several cases of lack of compliance to this. To reduce the amount of contact within red deer and between cervid species additional measures to limit the amount of silage dumped in fields may need to be installed. In addition, it may be necessary to enforce the requirement of fencing around hay bales to ensure compliance.

• Sørum, Ingrud; Mysterud, Atle; Rivrud, Inger Maren & Rauset, Geir Rune (2020). Use of salt licks by red deer (Cervus elaphus) in a disease transmission context. Universitetet i Oslo. Full text in Research Archive
• Rivrud, Inger Maren; Rolandsen, Christer Moe; Rauset, Geir Rune; Kvasnes, Mikkel Andreas Jørnsøn; Mysterud, Atle & Solberg, Erling Johan (2020). Hjorteviltpåkjørsler i Norge: Årsaksforhold, lokalisering, risiko og datakvalitet. Norsk institutt for naturforskning (NINA). ISSN 9788242645647. Full text in Research Archive Show summary

  Rivrud, I.M., Rolandsen, C.M., Rauset, G.R., Kvasnes, M., Mysterud, A. og Solberg, E.J. 2020. Hjorteviltpåkjørsler i Norge: Årsaksforhold, lokalisering, risiko og datakvalitet. NINA Rapport 1806. Norsk institutt for naturforskning. Antall viltpåkjørsler har økt kraftig de siste tiårene, med store konsekvenser i form av økonomiske og materielle kostnader, personskader, dødsfall og svekket dyrevelferd. Omfanget av spesielt hjorteviltpåkjørsler gjør dette til en av vår tids største utfordringer innen viltforvaltningen. Økningen i viltpåkjørsler har en klar sammenheng med økt tetthet i hjorteviltbestandene, men også høyere hastigheter, økt trafikkintensitet og utbygging av veg- og jernbanenettet spiller inn. Til tross for betydelig innsats fra det offentlige for å redusere viltulykker holder antallet seg relativt stabilt, og for noen arter, som rådyr og hjort, ser vi en viss økning. Det er derfor et tydelig behov for økt kunnskap om hvilke faktorer som påvirker påkjørslene, og hva som karakteriserer farlige strekninger. Mye fokus har vært rettet mot elgpåkjørsler, da disse har størst kostnad både materielt og i form av personskader. Énartsfokus er likevel ikke tilstrekkelig om man ønsker å identifisere de underliggende årsakene til viltpåkjørsler. Hjorteviltartene har ulike adferdsmønstre, de fordeler seg ulikt i landskapet lokalt og har ulik utbredelse nasjonalt. Det kan derfor være ulike risikoområder for artene. En komparativ tilnærming gir muligheter for å skille faktorer knyttet til bestandstetthet og adferd hos dyrene fra faktorer som er knyttet til trafikkbildet. Dette er avgjørende for å øke presisjonen i risikovarslingen. Det gir også mulighet for tiltak på steder der man kan redusere antallet påkjørsler for flere arter samtidig. Målet med denne rapporten er å øke kunnskapen og identifisere faktorene som kjennetegner områder med hyppige påkjørsler av artene elg, hjort og rådyr i Norge. Vi har undersøkt effekten av vilttetthet, arealtyper, snødybde og vegkategori på risiko for påkjørsel for de ulike artene, og hvordan sesong (sommer/vinter) kan påvirke effekten av disse faktorene. Vi har tilpasset modeller der vi undersøker detaljer i hvordan de ulike faktorene påvirker påkjørselsrisiko både hos de ulike artene enkeltvis, og alle artene i en og samme modell slik at forskjell i risiko for påkjørsel kan måles eksplisitt mellom arter. Fra modellene har vi bygget risikokarter for viltpåkjørsler over hele Norges offentlige vegnett. Avslutningsvis diskuterer vi kvaliteten på datagrunnlaget som finnes i de ulike databasene over påkjørsler. Modellene viser at faktorene som påvirker viltpåkjørslene er kompleks. Ulike landskapsfaktorer påvirker påkjørselsrisiko ulikt mellom arter og mellom sesonger. Bestandstetthet var den sterkeste påvirkningsfaktoren bak romlig variasjon i påkjørselsrisiko for alle arter, med høyere risiko for påkjørsel ved økende tetthet. Artene ble ulikt påvirket av landskapsvariabler. Elg og hjort, som beveger seg over store områder, hadde større samsvar mellom hva som påvirker påkjørselsrisiko sammenlignet med rådyr, som er mer stedfaste. Mens elg og hjort i større grad opplevde økt risiko med økende andel skog- og jordbruksareal rundt påkjørselspunktet, var andelen bebygd areal en viktigere påvirkningsfaktor for påkjørsler av rådyr. Elg og rådyr opplevde økt risiko i kommuner med større snødybde, mens dette ikke var tilfelle for hjort. Det kan i hovedsak skyldes at hjorten har sitt kjerneområde i vest, der kystklimaet gjør at mer nedbør faller som regn. Samtlige arter opplevde høyest risiko for påkjørsel på riksveger, tett etterfulgt av europaveger. Fylkesveger ga lavere risiko, mens kommunale veger lå nederst i risikospekteret. Dette reflekterer sannsynligvis en gradient i trafikkbelastning og fart, og til en viss grad også tiltak mot påkjørsler, som gjerne er størst på større veger som europaveger. Kartene over relativ risiko for påkjørsel for hele det offentlige vegnettet viser at modellene våre i stor grad predikerer høyere risiko i områder der det forekommer mange påkjørsler. Dette tyder på at modellene fungerer godt for å si noe om hvor tiltak for å begrense antallet viltpåkjørsler bør settes inn, og at kartene kan brukes som grunnlag for tiltak.

• Solberg, Erling Johan; Rivrud, Inger Maren; Nilsen, Erlend Birkeland; Veiberg, Vebjørn; Rolandsen, Christer Moe & Meisingset, Erling L. [Show all 7 contributors for this article] (2019). Bestandsreduksjon av elg og hjort i Nordfjella-regionen i perioden 2019-2020. Forslag til avskytingsstrategier. Norsk institutt for naturforskning (NINA). ISSN 9788242634139. Full text in Research Archive Show summary

• Vike, Brit Karen; Mysterud, Atle; Rivrud, Inger Maren & Meisingset, Erling L. (2016). Red deer migration and dietary quality: testing the role of landscape characteristics for the forage maturation hypothesis. Universitetet i Oslo. Full text in Research Archive Show summary

  The regular movement of animals between summer and winter ranges, termed seasonal migration, is a common phenomenon among ungulates at northern latitudes. The most prominent hypothesis to explain seasonal migration is the forage maturation hypothesis; it predicts that large herbivores will preferentially follow phenological (or green-up) gradients in order to access the highest possible forage quality with sufficient quantity. Surprisingly few studies provide empirical testing of the forage maturation hypothesis, and a question not often addressed is which landscape variables underlie the phenological gradient that makes migration a beneficial strategy. I tested the forage maturation hypothesis using the normalized difference vegetation index (NDVI), an index of plant phenology, and feces analyses as measures of forage quality and linked it with space use data from partially migratory red deer (Cervus elaphus) in Norway. Specifically, I investigated whether migratory individuals had access to higher quality forage than stationary, and the role of landscape variables for access to high quality forage. Generalized linear mixed models were used to analyze different measures of forage quality as responses to a set of covariates, including landscape variables. I found evidence that migratory red deer gain access to more high quality forage than stationary red deer, consistent with the forage maturation hypothesis. I found a positive effect of elevation on access to high quality forage for migratory individuals, and a diverse effect of other landscape characteristics, such as aspect and home range size. There was a positive effect of distance to fjord on accessed forage quality. This study sheds light on the relationship between the landscape an ungulate inhabit and the possibilities and limitations to access high quality forage within this landscape. Considering future climate change, and consequent changes in phenological gradients, it is important to understand the mechanisms causing the phenological gradients that migratory ungulates benefit from. Given the high diversity of impact by different variables found in this study, the effect of climate change may differ for populations across ecosystems.

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