The risk of viral transmissions from domestic and wild animals to humans is of high concern for human health. Humans can also transmit viral infections back to domestic and wild animals, which can then act as reservoir for the maintenance of viruses, with the risk of epidemic diseases re-emergence. The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), causing the COVID-19, likely originated from wildlife and has already been evidenced to be transmitted from humans to captive, domestic and wild animals. In particular, white-tailed deer ( Odocoileus virginianus ) show high-prevalence of SARS-CoV-2 following human contamination, and recent data suggest that white-tailed deer could act as an emerging virus reservoir. Here, we investigated whether SARS-CoV-2 could also have emerged in several longitudinally-monitored populations of European roe deer ( Capreolus capreolus ) in direct contact with humans in France. We performed indirect tests (serological ELISAs and seroneutralization) on serum collected pre- and post-emergence of the virus in human populations. We also performed direct tests (nasal swabs followed by RT-PCR) to detect the presence of SARS-CoV-2 RNA in those populations in 2022. We also investigated the exposure and prevalence of the virus in three other cervid species in France. ELISA tests were positive for 2.20 % of the sera tested, both pre- and post-emergence of the virus, but all positive samples were negative with seroneutralization. Direct PCR testing showed no positive results in 2022. Thus, although seroprevalence increased after the COVID-19 emergence (2022) in one out of three roe deer population, our results suggest that SARS-CoV-2 has not emerged in those populations, and that ELISA cross-reaction with another circulating virus, possibly an unidentified bovine coronavirus, is possible. ### Competing Interest Statement The authors have declared no competing interest.

Although global change and landscape modifications have degraded natural habitats, some species are able to thrive in anthropized landscapes by exploiting agricultural subsidies. In heterogeneous agroecosystems, spatial variation in landscape composition is predicted to impact demographic performance of wildlife depending on predominant agricultural practices and the distribution of remnant fragments of semi-natural habitat. Body mass is a key driver of among-individual variation in performance which varies at a fine scale, depending on landscape structure. We tested the hypothesis that the availability of rich crops (i.e. sorghum, corn and sunflower) in heterogeneous agricultural landscapes promotes rapid first-year growth of roe deer fawns, potentially driving spatial variation in demographic performance. We used GPS data of 166 juveniles (8–10 months old) inhabiting a heterogeneous agricultural landscape to predict their home range and evaluate its composition in terms of crops that may provide complementary resources. We hypothesized that juveniles with a post-weaning home range that included these crop types would be the heaviest at the onset of winter. Winter body mass of juveniles decreased by 35 ± 5 g per percentage point increase of woodland in their home range, so that juveniles with almost no woodland in their home range were about 3.5 kg heavier than those living in pure forest. Further, individuals with at least some corn in their home range were, on average, 773 ± 237 g heavier than those with none. Agricultural food subsidies reshape the habitat-dependent body mass trajectory of large herbivores, likely driving improved reproductive performance in agricultural landscapes.

Recent zoonotic disease emergences emphasize the importance of studying wildlife parasite communities. As wild hosts frequently harbour diverse parasite species, understanding the drivers of multiple infection patterns in free-ranging hosts is critical for elucidating the ecological and epidemiological dynamics of parasite communities. In this study, we analysed co-infection patterns in European roe deer (Capreolus capreolus) inhabiting a fragmented rural landscape in southwestern France. Using data from 130 samples of GPS-tracked deer, we examined the influence of proximity to livestock, host activity levels, age, sex and between-parasite interactions on the presence of 11 parasitic taxa. Hierarchical modelling of species communities (HMSC) revealed that proximity to livestock significantly increased the likelihood of infection with orofecally transmitted parasites (Toxoplasma gondii, gastrointestinal parasites). Sex and age were other key predictors, with males and juveniles exhibiting a higher frequency of parasite presence, likely influenced by hormonal and immune system differences. Activity levels showed distinct age-related effects, with higher activity levels being positively associated with increased parasite prevalence in yearlings, but not in adults. In contrast, parasite association patterns within individual hosts were weak, suggesting minimal interactions between parasite species. Our findings highlight the interplay between exposure and susceptibility in shaping co-infection patterns and underscore the value of hierarchical modelling approaches in multi-parasite systems.

Agricultural land use and climate change are major global threats to terrestrial biodiversity. However, their interactive effects on synanthropic species are only recently being addressed. Behavioural plasticity is the most likely candidate mechanism for coping with rapid environmental change, yet behavioural adjustments may be insufficient when multiple anthropogenic pressures, such as human land-use and rising temperatures, coincide with strong life-history constraints. We investigated how agricultural land use shaped the availability of thermal refuge and mediated responses to high temperatures during the mating season in roe deer (Capreolus capreolus), a large herbivore that is common in most European agricultural landscapes. We demonstrated that woodland provided more efficient thermal refuge than anthropogenic vegetation such as hedges or tall crops. The combination of high temperatures, agricultural land-use and reproductive constraints were dealt with differently by males and females. Females adjusted their habitat use and activity patterns to limit exposure to high temperatures, resulting in a greater loss in the availability of efficient cover habitat for females with little access to woodland. Males, however, did not modify their habitat use, but strongly decreased activity and distance travelled on hot days, probably due to strong reproductive constraints. We show that the extent to which behavioural plasticity mitigates the effects of high temperatures is context-dependent and may not always suffice in anthropized landscapes where thermal buffering habitats are rare. Restoring woodland patches and hedges, while considering how climate change modifies the use of substitute habitats shaped by human activities, will be key in promoting species' resilience within agricultural areas.

Understanding the behavioural adjustments of wildlife in anthropized landscapes is key for promoting sustainable human-wildlife coexistence. Little is known, however, about how synanthropic species navigate spatio-temporal variation in the availability of food and cover that are shaped by human practices such as agriculture. Animal habitat use is predominantly driven by spatial and temporal variations in food and cover, as individuals respond to fluctuations in the trade-off between food acquisition and risk avoidance. In agroecosystems, the availability of high-quality forage and cover are dependent on agricultural practices (e.g., harvesting) and crop phenology, providing an ideal opportunity to evaluate how wildlife adjust their behaviour in a heterogeneous human-dominated landscape. We investigated the influence of crop phenology on the behaviour of European roe deer (Capreoluscapreolus) to infer the functional roles of crop types in the food-cover landscape. We analysed the habitat use and activity patterns of 105 GPS-collared female roe deer using a unique dataset combining field-specific land cover data, region-specific estimates of crop phenology and weekly harvesting data for three common crops in a French agroecosystem. We found very distinct habitat use and activity patterns according to crop type, phenological stage and time of day. Wheat and artificial meadows were strongly selected at night-time during the early and post-harvest stages only, when roe deer were highly active, suggestive of feeding activity. On the contrary, roe deer strongly selected maize during the day when it was high enough to provide cover,when they were less active, indicating that it was primarily used for refuge. These patterns depended on the availability of more ‘natural’ cover, suggesting that mature maize may substitute for ‘natural’ cover when the latter is scarce. Our work highlights the importance of behavioural plasticity and habitat complementation in the persistence of this synanthropic species in agroecosystems. This behavioural adjustment may buffer the consequences of the reduction in natural habitats that accompanies intensification of agricultural production and has implications for understanding how agricultural practices shape the food-safety trade-off of wildlife living in these highly modified landscapes.

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

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

In variable environments, habitats that are rich in resources often carry a higher risk of predation. As a result, natural selection should favour individuals that balance allocation of time to foraging versus avoiding predation through an optimal decision-making process that maximizes fitness. The behavioural trade-off between resource acquisition and risk avoidance is expected to be particularly acute during gestation and lactation, when the energetic demands of reproduction peak. Here, we investigated how reproductive female roe deer adjust their foraging activity and habitat use during the birth period to manage this trade-off compared with non-reproductive juveniles, and how parturition date constrains individual tactics of risk-resource management. Activity of reproductive females more than doubled immediately following parturition, when energy demand is highest. Furthermore, compared with non-reproductive juveniles, they increased their exposure to risk by using open habitat more during daytime and ranging closer to roads. However, these post-partum modifications in behaviour were particularly pronounced in late-parturient females who adopted a more risk-prone tactic, presumably to compensate for the growth handicap of their late-born offspring. In income breeders, individuals that give birth late may be constrained to trade risk avoidance for foraging during peak allocation to reproduction, with probable consequences for individual fitness.

Understanding the consequences of global change for animal movement is a major issue for conservation and management. In particular, habitat fragmentation generates increased densities of linear landscape features that can impede movements. While the influence of these features on animal movements has been intensively investigated, they may also play a key role at broader spatial scales (e.g. the home range scale) as resources, cover from predators/humans, corridors/barriers or landmarks. How space use respond to varying densities of linear features has been mostly overlooked in large herbivores, in contrast to studies done on predators. Focusing on large herbivores should provide additional insights to understand how animals solve the trade-off between energy acquisition and mortality risk. Here, we investigated the role of anthropogenic (roads and tracks) and natural (ridges, valley bottoms and forest edges) linear features on home range features in five large herbivores. We analysed an extensive GPS monitoring database of 710 individuals across nine populations, ranging from mountain areas mostly divided by natural features to lowlands that were highly fragmented by anthropogenic features. Nearly all of the linear features studied were found at the home range periphery, suggesting that large herbivores primarily use them as landmarks to delimit their home range. In contrast, for mountain species, ridges often occurred in the core range, probably related to their functional role in terms of resources and refuge. When the density of linear features was high, they no longer occurred predominantly at the home range periphery, but instead were found across much of the home range. We suggest that, in highly fragmented landscapes, large herbivores are constrained by the costs of memorising the spatial location of key features, and by the requirement for a minimum area to satisfy their vital needs. These patterns were mostly consistent in both males and females and across species, suggesting that linear features have a preponderant influence on how large herbivores perceive and use the landscape.

Toll-like receptors (TLR) play a central role in recognition and host frontline defence against a wide range of pathogens. A number of recent studies have shown that TLR genes (Tlrs) often exhibit large polymorphism in natural populations. Yet, there is little knowledge on how this polymorphism is maintained and how it influences disease susceptibility in the wild. In previous work, we showed that some Tlrs exhibit similarly high levels of genetic diversity as genes of the Major Histocompatibility Complex (MHC), and signatures of contemporary balancing selection in roe deer (Capreolus capreolus), the most abundant cervid species in Europe. Here, we investigated the evolutionary mechanisms by which pathogen-mediated selection could shape this innate immunity genetic diversity by examining the relationships between Tlr (Tlr2, Tlr4 and Tlr5) genotypes (heterozygosity status and presence of specific alleles) and infections with Toxoplasma and Chlamydia, two widespread intracellular pathogens known to cause reproductive failure in ungulates. We showed that Toxoplasma and Chlamydia exposures vary significantly across years and landscape features with few co-infection events detected and that the two pathogens exert antagonistic selection on Tlr2 polymorphism. By contrast, we found limited support for Tlr heterozygote advantage. Our study confirmed the importance of looking beyond Mhc genes in wildlife immunogenetic studies. It also emphasized the necessity to consider multiple pathogen challenges and their spatiotemporal variation to improve our understanding of vertebrate defence evolution against pathogens.

Abstract The timing of birth has a predominant influence on both the reproductive success of the mother and the life‐history trajectory of her offspring. Because early growth and survival are key drivers of population dynamics, there is an urgent need to understand how global change is affecting reproductive phenology and performance. However, identifying when and where birth occurs is often difficult in the wild due to the cryptic behaviour of females around parturition, although this information may also help managers to protect reproductive females and newborn against human disturbance. While several approaches to identify parturition based on movement metrics derived from GPS monitoring have previously been proposed, their performance has not been evaluated over a range of species with contrasted movement characteristics. Here, we present a novel approach to detect parturition by combining data on animal movements, activity rate and habitat use. Using machine learning approaches, we evaluated the relative and combined performance of each category of metrics in predicting parturition for three large herbivores with contrasted life histories: a hider‐type species, the roe deer Capreolus capreolus and two follower‐type species, the Mediterranean mouflon Ovis gmelini musimon × Ovis sp. and the Alpine ibex Capra ibex. We first showed that detection of parturition was much improved when birth‐related modifications in the habitat use and activity rate of the mother were considered, rather than relying on movement metrics only. We then demonstrated that our approach was highly successful (76%–100% of events correctly identified) in detecting parturition in both follower and hider species. Furthermore, our approach generated estimates for peak birth date and the proportion of parturient females that were comparable with those based on direct observations at the population scale. Finally, our approach outperformed the most commonly employed methods in the literature which generally failed to identify non‐reproductive females for the three studied species, and provided birth timing estimates that only poorly match the true parturition date. We suggest that by combining sources of information, we have developed a standardised methodological approach for inferring parturition in the wild, not only for large herbivores but also for any species where parturition induces marked behavioural changes in the mother.

Life histories are strongly age dependent, notably linked to the onset of reproductive maturity and subsequent senescence. Consequently, ageing is predicted to impact behaviour, through the expression of either mating tactics in males or neonatal antipredator tactics in females. However, the influence of ageing, and the associated reproductive activity, on spatial behaviour remains poorly investigated. In this regard, we quantified ageand sex-specific intra-annual variation in movement rates and space use of two large herbivores with contrasting life histories: the roe deer, Capreolus capreolus, an asocial species with a territorial male mating strategy and a hider neonatal tactic, and the Mediterranean mouflon, Ovis gmelini musimon x Ovis sp., a gregarious species with a roaming male mating strategy and a follower neonatal tactic. We expected age-related differences to be mostly related to (1) age-specific mating tactics during the rut for males and the presence/absence of offspring for females, and (2) experience and/or locomotory senescence otherwise. During the rutting period, older roe deer males travelled greater daily distances than younger males due to patrolling behaviours for territory defence, whereas older mouflon males travelled less than younger males, which often adopted coursing tactics to mate with females. During the birth period, reproductive females had smaller home ranges than nonreproductive females in roe deer, whereas no marked differences were observed in mouflon females. The most marked age-related variation in space use of mouflon occurred outside the reproductive periods; specifically, the oldest individuals travelled less far and had a smaller home range (females only) than younger individuals. Our findings illustrate how space use tactics vary within and between populations of large herbivores, providing strong evidence that age and reproductive activity are major determinants of their spatial behaviour. (c) 2020 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Because of their continuing expansion, wildlife ruminant species that prosper in rural landscapes may be increasingly affected by and/or contribute to the circulation of certain generalist pathogens also infecting domestic ruminants, when they share common spaces or resources. In this study, we aimed to test the hypothesis that parasitism with gastrointestinal nematodes (GINs) of wild roe deer inhabiting different rural landscapes is correlated with livestock density. We used faecal egg counts of GINs and spatial data of 74 GPS-collared roe deer, inhabiting various landscapes from closed forests to open fields, together with weekly records of livestock abundances on pasture. We tested whether the excretion of GIN eggs in roe deer was influenced by the density of livestock in their home range over the grazing season. Our results showed that all of the roe deer home ranges, except four, contained pastures occupied by livestock. Excretion of GIN eggs occurred in 77% of the roe deer. The excretion of GIN eggs in roe deer tended to increase with livestock density in their home range. This result suggests, but does not prove, a higher risk of ingesting GIN larvae originating from livestock dung. In the context of increasing overlap between roe deer and livestock ranges, the exchange of pathogens between both hosts is plausible, although species identity of the parasites present was not determined. Assessing which GIN species are shared between wild and domestic ruminants, and how this may affect the health of both hosts, is a central question for future research in the context of interspecific pathogen circulation.

Wildlife populations are increasingly exposed to human-induced modifications of their habitats. To cope with anthropogenic stressors, animals can adjust their behaviour-for example, by shifting their activity to more sheltered habitats, or becoming more nocturnal. However, whether use of spatial and temporal adjustments in behaviour may regulate the endocrine response is poorly documented. Here, we analyzed faecal cortisol metabolites (FCMs) of wild roe deer (Capreolus capreolus) living in a human-dominated agro-ecosystem. Using Global Positioning System monitoring of 116 individuals, we assessed their spatial behaviour and tested whether proximity to anthropogenic structures (linear distance to built-up areas) and the use of refuge habitats (woodland and hedges) influenced FCM levels. In accordance with our predictions, individuals ranging closer to anthropogenic structures during daytime had higher FCM levels, but this relationship was buffered as use of refuge habitat increased. In addition, this link between proximity to anthropogenic structures and FCM levels disappeared when we analyzed spatial behaviour at night. Finally, FCM levels were higher when the ambient temperature was lower, and during years of low resource availability. Our results demonstrate that the stress levels of large mammals may be strongly influenced by their proximity to anthropogenic activities, but that these effects may be buffered by behavioural adjustments in terms of space use and circadian rhythm. Whereas most studies have focused on the influence of environmental heterogeneity, our analysis highlights the need to also consider the fine-scale spatial response of individuals when studying the hormonal response of wild animals to human disturbance. We emphasize the potential to mitigate this hormonal stress response, and its potential negative consequences on population dynamics, through the preservation or restoration of patches of refuge habitat in close proximity to human infrastructure.

Assessing the evolutionary potential of animal populations in the wild is crucial to understanding how they may respond to selection mediated by rapid environmental change (e.g. habitat loss and fragmentation). A growing number of studies have investigated the adaptive role of behaviour, but assessments of its genetic basis in a natural setting remain scarce. We combined intensive biologging technology with genome-wide data and a pedigree-free quantitative genetic approach to quantify repeatability, heritability and evolvability for a suite of behaviours related to the risk avoidance-resource acquisition trade-off in a wild roe deer (Capreolus capreolus) population inhabiting a heterogeneous, human-dominated landscape. These traits, linked to the stress response, movement and space-use behaviour, were all moderately to highly repeatable. Furthermore, the repeatable among-individual component of variation in these traits was partly due to additive genetic variance, with heritability estimates ranging from 0.21 ± 0.08 to 0.70 ± 0.11 and evolvability ranging from 1.1% to 4.3%. Changes in the trait mean can therefore occur under hypothetical directional selection over just a few generations. To the best of our knowledge, this is the first empirical demonstration of additive genetic variation in space-use behaviour in a free-ranging population based on genomic relatedness data. We conclude that wild animal populations may have the potential to adjust their spatial behaviour to human-driven environmental modifications through microevolutionary change.

Dispersal is a key mechanism enabling species to adjust their geographic range to rapid global change. However, dispersal is costly and environmental modifications are likely to modify the cost-benefit balance of individual dispersal decisions, for example, by decreasing functional connectivity. Dispersal costs occur during departure, transience and settlement, and are levied in terms of energy, risk, time and lost opportunity, potentially influencing individual fitness. However, to the best of our knowledge, no study has yet quantified the energetic costs of dispersal across the dispersal period by comparing dispersing and philopatric individuals in the wild. Here, we employed animal-borne biologgers on a relatively large sample (N = 105) of juvenile roe deer to estimate energy expenditure indexed using the vector of dynamic body acceleration and mobility (distance travelled) in an intensively monitored population in the south-west of France. We predicted that energy expenditure would be higher in dispersers compared to philopatric individuals. We expected costs to be (a) particularly high during transience, (b) especially high in the more fragmented areas of the landscape and (c) concentrated during the night to avoid disturbance caused by human activity. There were no differences in energy expenditure between dispersers and philopatric individuals during the pre-dispersal phase. However, dispersers expended around 22% more energy and travelled around 63% further per day than philopatric individuals during transience. Differences in energy expenditure were much less pronounced during the settlement phase. The costs of transience were almost uniquely confined to the dawn period, when dispersers spent 23% more energy and travelled 112% further than philopatric individuals. Finally, the energetic costs of transience per unit time and the total distance travelled to locate a suitable settlement range were higher in areas of high road density. Our results provide strong support for the hypothesis that natal dispersal is energetically costly and indicate that transience is the most costly part of the process, particularly in fragmented landscapes. Further work is required to link dispersal costs with fitness components so as to understand the likely outcome of further environmental modifications on the evolution of dispersal behaviour.

Although inter‐individual heterogeneity in many aspects of dispersal behaviour is widely reported, this key life‐history trait is predominantly modelled as a dichotomous state of philopatry versus dispersal. The increasing body of evidence for dispersal syndromes (i.e. a suite of correlated morphological, behavioural and life‐history traits associated with dispersal) implies substantial but, to date, undocumented individual heterogeneity in behavioural tactics during dispersal. Using a large sample (n = 154) of GPS monitored juvenile roe deer Capreolus capreolus , we evaluated among‐individual behavioural heterogeneity in dispersal tactics, and the individual and environmental drivers of these alternative tactics. We developed a sequential three‐stage decision tree based on space use stability, exploration events and the directionality of movement. We identified six discrete alternative behavioural tactics during the dispersal period which were characterised by different timing, amplitude and duration in movement: slightly less than half of the deer were sedentary, either ‘strictly philopatric’ or ‘explorers’, which subsequently settled on their natal range; around 40% dispersed (‘classic dispersal’), of which, one in six subsequently aborted, moving back to their natal range (‘aborted dispersal’); finally, around 15% expressed either a ‘progressive dispersal’ tactic, gradually moving away from their natal area to settle elsewhere, or a ‘multi‐range’ tactic. The propensity to express an alternative dispersal tactic was strongly influenced by an individual's local environment. In particular, when landscape heterogeneity, resource quality and human‐related disturbance in the natal range were low, individuals were 1) more likely to adopt the alternative tactics of either progressive dispersal or multi‐ranging, but 2) also more likely to abort their dispersal attempt. Our work indicates that natal dispersal is likely not a single uniform behaviour, but that individuals may adopt a variety of alternative movement tactics which are likely governed by different selection pressures, with potentially important impacts for population dynamics and functioning.

The reduction in biodiversity from land use change due to urbanization and agricultural intensification appears to be linked to major epidemiological changes in many human diseases. Increasing disease risks and the emergence of novel pathogens result from increased contact among wildlife, domesticated animals, and humans. We investigated the relationship between human alteration of the environment and the occurrence of generalist and synanthropic rodent species in relation to the diversity and prevalence of rodent-borne pathogens in Southeast Asia, a hotspot of threatened and endangered species, and a foci of emerging infectious diseases. We used data from an extensive pathogen survey of rodents from seven sites in mainland Southeast Asia in conjunction with past and present land cover analyses. At low spatial resolutions, we found that rodent-borne pathogen richness is negatively associated with increasing urbanization, characterized by increased habitat fragmentation, agriculture cover and deforestation. However, at a finer spatial resolution, we found that some major pathogens are favored by environmental characteristics associated with human alteration including irrigation, habitat fragmentation, and increased agricultural land cover. In addition, synanthropic rodents, many of which are important pathogen reservoirs, were associated with fragmented and human-dominated landscapes, which may ultimately enhance the opportunities for zoonotic transmission and human infection by some pathogens.

Understanding how wild animals adapt to perturbations and their consequences for life history traits and population dynamics is a current focus of attention in ecology and conservation biology. Here, we analysed variation in the neutrophil to lymphocyte ratio (N:L ratio), a proxy of stress level, in wild roe deer Capreolus capreolus from three populations experiencing markedly different environmental conditions. We first assessed whether among-individual differences in the N:L ratio were consistent over time and across environmental contexts. We then investigated how both individual characteristics (behaviour at capture, age, sex, body mass), and environmental context (habitat and year quality) were linked to this indicator of stress level. We found moderate, but consistent, repeatability of the N:L ratio in all three populations, indicating stable among-individual differences in the way individuals cope physiologically with varying environmental conditions. In addition, we found a weak, but consistent, association between the N:L ratio and behaviour at capture in two of the three populations. Finally, the N:L ratio also varied in relation to temporal changes in environmental conditions. In particular, individuals had, on average, higher levels of stress in poor-quality years in two of the three populations. We discuss our results in relation to the coping styles framework. Due to global change, natural populations are increasingly faced with unpredictable fluctuations of their environment. The stress response, via the release of glucocorticoids, is a key mechanism that enables individuals to cope with these variations. However, all individuals do not necessarily cope with life threatening and/or stressful situations in the same way, but as yet, the major drivers underlying variation in stress level remain unclear. We showed that the N:L ratio, reflecting baseline stress level, was repeatable and influenced by both individual and environmental factors. In particular, variation in the N:L ratio was linked to the quality of the year in terms of resource availability and, to a lesser extent, to the individual’s behaviour at capture. Our study demonstrates that both environmental context and individual characteristics drive variation in the N:L ratio in a wild vertebrate population.

The Rattini tribe comprises some of the most specious genera in the mammalian kingdom. Many of these species are also highly morphologically conserved. As a result, identifying Rattini tribe animals, particularly those of the Rattus genus, to species level is extremely difficult. Problems with identification of conservative morphologies, particularly of the skeleton, have led to difficulties in understanding the fossil remains and as a result the systematics of this group. Here, we apply geometric morphometrics to the first lower molar of 14 species of the Rattini tribe. We find that the morphological data present a strong phylogenetic signal. However, within Rattus, this signal is rather complex and possibly hints at rapid evolutionary shape and size changes. In modern species, it is possible to identify specimens to species level with a good degree of confidence. We find that using both size and shape together affords further confidence with identification. However, we caution against the over-reliance on size in environments with unknown species composition and climate, particularly in archaeological contexts. This approach should prove to be a useful tool for identifying fossil and sub-fossil remains, particularly where biomolecular markers are absent in circumstances of poor preservation.