#AgriDeer: Damage and beyond: role of farmland for red deer populations (completed)

• 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.

• Omholt, Stig William; Gamelon, Marlene & Meisingset, Erling L. (2025). Robust abundance estimation of harvested populations from low quality time series data: A red deer case study. Ecological Indicators. ISSN 1470-160X. 173. doi: 10.1016/j.ecolind.2025.113398. Full text in Research Archive Show summary

  Reliable estimates of the size and composition of harvested populations over time are key to designing adequate population management plans, regardless of management objectives. In Norway, a national system for collecting and analysing hunter-reported data on red deer (Cervus elaphus) has been operational for about 20 years. The system was expected to provide population metrics that would substantially improve deer population management routines at the municipal level. This has proven to be challenging when using existing state-of-the-art estimation methodology. The main reasons are that the variation in the observation data is generally much larger than population abundance variability, and that one does not have a clear understanding of the stochastic process generating the observation data. Here, using hunter-reported observation data and harvest data from six Norwegian municipalities collected in the period 2007–2023, we show that a straightforward estimation methodology based on population modelling can produce robust abundance estimates despite frequent low quality of the observation data. Its major assets are that it does not involve strong assumptions about the stochastic processes underlying the observation process and that it does not involve assumptions about initial population size and structure in terms of prior statistical distributions. We anticipate that the method can be applied in several other population management contexts, and we think that the results offer fresh perspectives on to what extent noisy citizen-collected time series data can be used to inform management decisions.

• 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.

• Vindenes, Yngvild; Langvatn, Rolf & Mysterud, Atle (2023). Shifting seasonality of annual growth through ontogeny for red deer at northern latitudes. Ecosphere. 14(8), p. 1–11. doi: 10.1002/ecs2.4639. Full text in Research Archive Show summary

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

• 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.

• 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.

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• Unsgård, Even (2025). Red deer damage and disease risk in sympatric cervids. Full text in Research Archive
• Unsgård, Even (2025). Red deer damages on economically important forest trees and agricultural meadows. Full text in Research Archive
• Unsgård, Even (2025). Skademareitt? Beiteskade på innmark og barkgnag på gran. Full text in Research Archive
• Unsgård, Even (2025). Skademareritt: Hjorten sin påvirkning på innmark og utmark. Full text in Research Archive
• Unsgård, Even; Meisingset, Erling L. & Mysterud, Atle (2025). Store variasjoner i avlingstapet til hjort. NIBIO POP. ISSN 2464-1170. 11(55). Full text in Research Archive Show summary

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

• Unsgård, Even (2025). #AgriDeer: Hjortens bruk av innmark og utmark. Full text in Research Archive
• Mysterud, Atle (2024). #AgriDeer: Damage and beyond: role of farmland for red deer populations. Full text in Research Archive
• Hjermann, Tilde (2023). Sex-specific use and selection of agricultural farmland by a partially migratory ungulate. Full text in Research Archive
• Hjermann, Tilde (2023). Use and selection of agricultural farmland by a partially migratory ungulate. Full text in Research Archive
• Hjermann, Tilde (2023). Red deer and agricultural farmland: Use, selection and migration timing. Full text in Research Archive
• Mysterud, Atle & Holthe, Vidar (2021). Hva betyr innmarka for hjorten - og hjorten for innmarka? p. 19–19. Full text in Research Archive
• 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.

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