Tilde Katrina Slotte Hjermann

• 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.

• Rueness, Eli Knispel; Boer, Hugo de; Gehrke, Berit; Hjermann, Tilde; Thorstad, Eva Bonsak & Grainger, Matthew [Show all 10 contributors for this article] (2025). Scientific assessment of risk from trade to CITES-listed species of sturgeons and paddlefishes. VKM Report. 2025:06, p. 1–97. Full text in Research Archive Show summary

  The Norwegian Scientific Committee for Food and Environment (VKM) has assessed whether trade with sturgeons is a risk to wild populations. For two out of eleven species, international trade is considered non-detrimental to their survival. For the remaining nine species, all trade with wild-caught fish is considered detrimental, while VKM is unable to determine whether trade with fish from aquaculture will be detrimental to the species’ survival due to lack of information. VKM is the national Scientific Authority for the Convention on International Trade with Endangered Species of Wild Fauna and Flora (CITES). We have assessed the potential detriment of international trade to sturgeons on assignment from the Norwegian Environment Agency (NEA), who are the national Management Authority under CITES. The risk assessment will be used by NEA for processing import/export permits for sturgeons and products thereof, such as caviar, in compliance with the Norwegian CITES Regulation. The assessment comprises eleven species of sturgeons and paddlefishes, of which ten have been imported to or exported from Norway the past ten years. The last species is commonly traded internationally but has yet not been imported to or exported from Norway. For each species, the assessment is based on knowledge of the species’ biology, environment, use, and level of trade. For two of the eleven species that have been assessed, international trade does not pose a threat to their survival in the wild. For the remaining nine species, all trade with wild-caught fish will be detrimental to their survival. For fish and products of fish from aquaculture, VKM is unable to determine whether international trade is detrimental to the species’ survival in the wild, as the available information on the impact of aquaculture on wild populations is conflicting and insufficient. Trade is not detrimental for the following species: Acipenser transmontanus, Polyodon spathula Not concluded for the following species: Acipenser baerii, Acipenser gueldenstaedtii, Acipenser naccarii, Acipenser persicus, Acipenser ruthenus, Acipenser schrenckii, Acipenser stellatus, Huso dauricus, Huso huso “Sturgeons is the most threatened group of species on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Even though most of the trade is with fish from aquaculture, the level of uncertainty regarding consequences for the wild populations is high,” says Scientific Leader Eli K. Rueness. VKM proposes that the risk assessment for each species could be applied for a period of five years, unless the IUCN Red List publishes updated assessments where any of the species are given a higher risk category.

• Hjermann, Tilde Katrina Slotte; Herfindal, Ivar; Ratikainen, Irja Ida; Strand, Olav & Rauset, Geir Rune (2024). Individual and temporal variation in movement patterns of wild alpine reindeer and implications for disease management. Ecography. ISSN 0906-7590. 10(10), p. 1–12. doi: 10.1111/ecog.06957. Full text in Research Archive Show summary

  Animal behaviour is important for prevalence and outbreaks of infectious diseases, for instance by affecting individual interactions. Increasing the knowledge of individual movement patterns can provide better insight into disease prevalence and spread, helping to target efforts to minimise disease outbreaks. Chronic wasting disease (CWD) is a fatal prion disease affecting cervids. CWD is transmitted by animal-to-animal contact and through the environment, thus individual variation in space use and social associations may influence disease transmission patterns and infection risk. CWD was detected in Norwegian alpine reindeer Rangifer tarandus tarandus in 2016, and eradication of the infected population was implemented. A 3:1 infection rate between males and females suggests sex-specific behavioural drivers. We utilised an extensive individual-based dataset of 149 GPS-marked wild reindeer to investigate individual variation in movement patterns in terms of inter- and intra-annual home range size and site fidelity, and variation in home range overlap and distances between individuals. We aimed to identify patterns which could indicate higher potential disease risk. Females had larger annual and seasonal home ranges than males, except during calving and rut. Greater home range overlaps and shorter between-individual distances were found between same-sex individuals than different-sex individuals, except during the rut. Accordingly, the rut season stands out with greater male home ranges, greater home range overlap and shorter distances between males and between males and females, which could indicate that this season is critical for disease transmission. Measures to prevent disease spread should lower contact rates, e.g. by reducing the abundance of adult males before they mix with other groups during the rut. This can be achieved for instance by allowing earlier hunt on adult males when they are distributed in small male groups, to reduce the transmission risk and keep disturbance of other individuals low.

• 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.

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• 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
• Grainger, Matthew; Eldegard, Katrine; Hjermann, Tilde; Kopatz, Alexander; Rueness, Eli Knispel & Boer, Hugo de (2025). Non-detriment finding for Bali myna (Leucopsar rothschildi). VKM Bulletin. p. 1–5. Full text in Research Archive Show summary

  Innførsel av en levende balistær (Leucopsar rothschildi) avlet i fangenskap fra en dyrehage i Danmark til en dyrehage i Norge vil ikke være til skade for artens bevaringsstatus. Vurderingen ble gjort på oppdrag fra Miljødirektoratet, som er forvaltningsmyndighet for Konvensjonen om internasjonal handel med truede arter av vill flora og fauna, CITES, i Norge. VKM er vitenskapelig myndighet for CITES i Norge, og utarbeider vitenskapelige vurderinger (såkalte ‘non-detriment findings’) i tråd med metodikk publisert av Verdens naturvernunion (IUCN) og CITES.

• Hjermann, Tilde K. S. (2025). Har du en krokodille i skapet? Forskning.no. ISSN 1891-635X. Full text in Research Archive
• Boer, Hugo de; Grainger, Matthew; Hjermann, Tilde; Kopatz, Alexander & Rueness, Eli Knispel (2025). Non-detriment finding for sperm whale (Physeter macrocephalus). VKM Bulletin. VKM Bulletin(VKM Bulletin 2025: 06), p. 1–5. Full text in Research Archive Show summary

  Export of 10 pre-Convention sperm whale teeth (Physeter macrocephalus) from Norway to Fiji and 10 to USA will not be detrimental to the survival of the species. Export of 10 pre-Convention sperm whale teeth (Physeter macrocephalus) from Norway to Fiji and 10 to USA will not be detrimental to the survival of the species. Thus concludes the Norwegian Scientific Committee for Food and Environment (VKM). The assessment was commissioned by the Norwegian Environment Agency, which is the management authority for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Norway. VKM is the scientific authority for CITES in Norway and prepares non-detriment finding (NDF) reports in accordance with the methodology published by the International Union for Conservation of Nature (IUCN) and CITES.

• Kopatz, Alexander; Hjermann, Tilde; Rueness, Eli Knispel & Boer, Hugo de (2025). Non-detriment finding for scimitarhorned oryx (Oryx dammah). VKM Bulletin. VKM Bulletin(VKM Bulletin 2025: 08), p. 1–6. Full text in Research Archive Show summary

  Import of one hunting trophy of scimitar-horned oryx (Oryx dammah) from South Africa to Norway will not be detrimental to the survival of the species. Thus concludes the Norwegian Scientific Committee for Food and Environment (VKM). The assessment was commissioned by the Norwegian Environment Agency, which is the management authority for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Norway. VKM is the scientific authority for CITES in Norway and prepares non-detriment finding (NDF) reports in accordance with the methodology published by the International Union for Conservation of Nature (IUCN) and CITES.

• Kopatz, Alexander; Hjermann, Tilde; Rueness, Eli Knispel & Boer, Hugo de (2025). Non-detriment finding for Lau banded iguana (Brachylophus fasciatus). VKM Bulletin. VKM Bulletin(VKM Bulletin 2025: 07), p. 1–5. Full text in Research Archive Show summary

  Import of one live Lau banded iguana (Brachylophus fasciatus) from a zoo in Denmark to a zoo in Norway will not be detrimental to the survival of the species. Thus concludes the Norwegian Scientific Committee for Food and Environment (VKM). The assessment was commissioned by the Norwegian Environment Agency, which is the management authority for the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) in Norway. VKM is the scientific authority for CITES in Norway and prepares non-detriment finding (NDF) reports in accordance with the methodology published by the International Union for Conservation of Nature (IUCN) and CITES.

• Rueness, Eli Knispel; Eldegard, Katrine; Gehrke, Berit; Hjermann, Tilde; Kopatz, Alexander & Boer, Hugo de (2024). Non-detriment finding for Sumatran orangutan. VKM Bulletin. VKM Bulletin 2024: 28(VKM Bulletin 2024: 28), p. 1–4. Full text in Research Archive
• Hjermann, Tilde; Grainger, Matthew; Hermansen, Jo Skeie; Rueness, Eli Knispel & Boer, Hugo de (2024). Non-detriment finding for Guianan squirrel monkey. VKM Bulletin. VKM Bulletin 2024: 25(VKM Bulletin 2024: 25), p. 1–6. Full text in Research Archive Show summary

  (Re-)utførsel av to levende ekornaper (Saimiri sciureus) avlet i fangenskap fra dyrehage i Norge til dyrehage i Israel vil ikke være til skade for artens bevaringsstatus. Det konkluderer Vitenskapskomiteen for mat og miljø (VKM). Vurderingen ble gjort på oppdrag fra Miljødirektoratet, som er forvaltningsmyndighet for Konvensjonen om internasjonal handel med truede arter av vill flora og fauna, CITES, i Norge. VKM er vitenskapelig myndighet for CITES i Norge, og utarbeider vitenskapelige vurderinger (såkalte ‘non-detriment findings’) i tråd med metodikk publisert av Verdens naturvernunion (IUCN) og CITES.

• Rueness, Eli Knispel; Eldegard, Katrine; Hjermann, Tilde; Kopatz, Alexander & Boer, Hugo de (2024). Non-detriment finding for ringtailed lemur. VKM Bulletin. VKM Bulletin 2024: 29(VKM Bulletin 2024: 29), p. 1–4. Full text in Research Archive Show summary

  Utførsel av fire levende ringhalelemurer (Lemur catta) avlet i fangenskap fra en dyrehage i Norge til en dyrehage i Danmark vil ikke være til skade for artens bevaringsstatus. Det konkluderer Vitenskapskomiteen for mat og miljø (VKM). Vurderingen ble gjort på oppdrag fra Miljødirektoratet, som er forvaltningsmyndighet for Konvensjonen om internasjonal handel med truede arter av vill flora og fauna, CITES, i Norge. VKM er vitenskapelig myndighet for CITES i Norge, og utarbeider vitenskapelige vurderinger (såkalte ‘non-detriment findings’) i tråd med metodikk publisert av Verdens naturvernunion (IUCN) og CITES. Del denne side

• 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; 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.

• 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.

• Hjermann, Tilde; Ratikainen, Irja Ida; Herfindal, Ivar & Rauset, Geir Rune (2021). Sex-specific space use patterns in wild alpine reindeer: potential consequences for disease transmission. Norges teknisk-naturvitenskapelige universitet. Full text in Research Archive Show summary

  Dyrs bevegelsesmønstre påvirker mange økologiske prosesser, som til syvende og sist påvirker individets fitness. I tillegg til den romlige skalaen av individets bevegelser, for eksempel målt i størrelsen på sesongmessige eller årlige hjemmeområder, vil et individs romlige bruksmønster og overlapp med andre individer ha store fitnesskonsekvenser, og blant annet påvirke dets mottagelighet for sykdommer. Mens årsaker og konsekvenser av individuelle mønstre i områdebruk er godt studert i en rekke artsgrupper, vet vi mindre om hvor konsistente individuelle bevegelsesmønstre er over tid, det vil si dets grad av stedstrohet, samt individers romlige interaksjonsmønstre. Romlige bevegelsesmønstre kan dermed være viktige for forståelsen av smittespredningsdynamikk, som kan være essensielt for kontroll og forvaltning av sykdommer i en populasjon. Villrein (Rangifer tarandus tarandus) er et migrerende hjortedyr som lever i sosiale flokker. Flokkstørrelse og -sammensetning varierer gjennom året, og bukker og simler er stort sett i separate grupper unntatt under brunsten. Bukkene, som er større enn simlene, er grunnet høyere metabolske behov forventet å ha større hjemmeområdestørrelse enn simlene. Men simlene danner imidlertid større flokker, som motvirker effekten av bukkenes større kroppsstørrelse på hjemmeområdestørrelse. Nylig ble den fatale sykdommen skrantesjuke (Chronic wasting disease, CWD) påvist i en villreinpopulasjon i Norge. Studier av denne og andre smittede hjortedyrpopulasjoner i Nord-Amerika viser til en høyere CWD-prevalens hos bukker sammenliknet med simler. Forskjeller i områdebruk har blitt foreslått som potensiell årsaksfaktor, da CWD smitter både gjennom direkte kontakt og indirekte gjennom miljøet. Skalaen av individuell områdebruk og hvordan de overlapper med andre individer i tid og rom er dermed viktig for hastigheten av CWD-smitte i en populasjon. Følgelig brukte jeg GPS-data til å studere mønstre i villreinens områdebruk i tre populasjoner i Norge. I alle populasjoner var både årlig og sesongmessig hjemmeområdestørrelse større hos simlene enn bukkene, unntatt i brunsten. Mellom-års stedstrohet var lik for begge kjønn. Innen-års stedstrohet var imidlertid større for simler i to av tre populasjoner. Overlapp i sesonghjemmeområde var større mellom individer av samme kjønn sammenliknet med individer av motsatt kjønn, unntatt under brunsten hvor overlappen mellom både bukk – simle og bukk – bukk økte. Disse mønstrene indikerer at brunstsesongen er viktig for smittespredning i en populasjon. Resultatene fra dette studiet viser konsistente mønstre av seksuell differensiering i områdebruk hos villrein, vist gjennom kjønnsspesifikke hjemmeområdestørrelser og -overlapp, og til en viss grad stedstrohet. Disse forskjellene i områdebruk kan dermed være viktig for smittespredningsmønstre i en populasjon.

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