Abstract Nutritional resources during summer are important for supporting fat accretion, growth, survival, and reproduction and generally set upper limits on population productivity. We aimed to quantify the nutritional resources in plant communities available to endangered Sierra Nevada bighorn sheep ( Ovis canadensis sierrae ; hereafter Sierra bighorn) during summer and evaluate whether forage quantity (biomass) and forage quality (digestible energy [DE], crude protein [CP]) were adequate to meet nutritional requirements of Sierra bighorn in California, USA. From June through August 2017–2018, we sampled forage biomass in 5 plant communities (barren, dry shrub, herbaceous dry, herbaceous wet, and wet shrub) available to Sierra bighorn using double‐sampling techniques, and assayed 2018 forage samples for DE and CP content. We related DE and CP content within plant communities to nutritional requirements of lactating Sierra bighorn. All 5 plant communities sampled provided adequate CP to meet nutritional requirements for lactation, whereas only 4 of 5 plant communities provided adequate forage biomass and only 2 of 5 plant communities provided adequate DE. Wet shrub plant communities provided the greatest forage biomass and high levels of CP and DE for Sierra bighorn during summer, and barren communities provided the least forage biomass. Combined forage biomass and forage quality data suggested nutritional value was greatest in wet shrub communities, followed by herbaceous wet, dry shrub, herbaceous dry, and barren. Our findings indicate that DE and, to a lesser extent, forage biomass during summer set an upper limit for population productivity of Sierra bighorn, but CP did not. Understanding the nutritional value of plant communities available to Sierra bighorn during summer can help inform recovery efforts, including translocations, and provide a biological basis for recovery goals relative to nutrition.

Neonate survival is among the primary demographics underpinning ungulate populations. Though few studies have quantified handling-induced effects on neonates, there is concern from stakeholders that handling neonates affects survival. In response, handling protocols often contain conservative procedures to reduce potential negative effects of handling on survival. Handling protocols may lack data-based support and are based largely on anecdotal evidence and untested assumptions. We used 7 datasets from mule deer (Odocoileus hemionus), Rocky Mountain bighorn sheep (Ovis canadensis canadensis), and desert bighorn sheep (Ovis canadensis nelsoni) to evaluate the relationship between neonatal capture and handling with survival. We evaluated capture and handling effects at 2 demographic scales. First, we tested whether variation in aspects of the handling process was associated with variation in probability of mortality. Second, we compared survival to weaning of captured versus uncaptured neonates. We detected a negative effect of neonate age at capture (probability of mortality increased 28% from 24 to 48 hours old) and the number of collectors present (probability of mortality decreased 16% from 1 to 3 collectors) on survival within the first 72 hours following capture in bighorn sheep. We detected an effect of handling time in neonates perceived to be abandoned, but the direction of the effect in mortality differed between bighorn sheep (probability of mortality increased 20% from 5 to 25 minutes) and mule deer (probability of mortality decreased 3% from 5 to 25 minutes). In bighorn sheep, the negative effect of handling time was driven by a single, unusually long handling time. Following removal of the outlier, handling time no longer had a significant effect on the probability of survival. We detected no difference in the probability of survival to weaning between individuals we captured versus those we did not capture in either species. Broad censoring of post-capture mortalities perceived to be associated with handling may not be the result of capture-induced mortality, and this censoring may result in a loss of biological information or yield misleading results in survival analyses. Our research supports that handling processes associated with the neonate captures remain a viable approach to studying this vital demographic.

Understanding the relationships between nutrition and life-history characteristics can provide insight into the factors limiting populations. Moose (Alces alces) at their southern range periphery are subject to nutritional constraints because of marginal climatic and habitat conditions, but how these limitations influence vital rates remains a point of uncertainty. We examined the nutritional and reproductive dynamics of moose at the fringes of their range in southeast Wyoming, USA. We used an individual-based approach to evaluate the nutritional condition (i.e., body fat) of female moose by recapturing the same individuals each autumn and spring to measure body fat, pregnancy, recruitment of offspring, and survival. Like other temperate ungulates, we anticipated that moose would accumulate body fat over summer and use those reserves to support survival and reproduction over winter. Throughout the annual cycle, we expected that body fat, an integrated measure of energetic gains and losses, would influence pregnancy, recruitment, and adult survival. Contrary to expectations, body fat varied by less than 1.5 percentage points between autumn and spring. Despite relatively low seasonal fluctuations, body fat was positively associated with probability of pregnancy and adult survival but did not influence recruitment of young. Moreover, age influenced probability of pregnancy and overwinter survival. We demonstrate clear signs of nutritional limitation and unexpectedly absent relationships between body fat and recruitment that may be unique to moose living at the fringes of their range, highlighting environmental constraints on reproduction at distributional limits. By investigating the connections between nutrition and reproduction in southern moose, we provide insight into how vital rates can be used to monitor demographic performance for at-risk populations.

Animals face declining fitness contributions near the end of life, termed reproductive senescence. Though reproductive senescence frequently stems from physiological inefficiencies, animals making their final attempts at reproduction have the greatest incentive to succeed, raising the question of whether this deterioration is inevitable or if they can compensate to enhance fitness. Here, we examined whether foraging effort serves as behavioural compensation for reproductive senescence in female mule deer (Odocoileus hemionus). We expected that, as animals approach the end of their lifespans, they would increase foraging effort as a means of compensating for declining reproductive output. To assess compensatory foraging, we disentangled two components of lifetime fitness: energy acquisition and allocation. We used animal-borne activity sensors to quantify foraging effort (time devoted to energy acquisition) and followed animals across the annual cycle to measure reproductive output and seasonal fluctuations in stored energy (body fat). Then, we evaluated whether foraging effort mediated the effect of age on allocation to current reproduction and future fitness contributions. For senescing animals, foraging effort positively influenced newborn size, providing evidence of compensation for declining fitness contributions. Moreover, we detected a possible diversion of resources away from future survival and to current reproduction. Senescing animals with high foraging effort accumulated little fat over summer, likely diverting incoming energy to finance current reproduction (lactation) over future fitness. Our work demonstrates that, facing their final opportunities to reproduce, animals may use behaviour to compensate for the physiological declines associated with aging to improve their chances of reproductive success. By evaluating the role of behaviour in fitness components, we reveal processes underlying senescence, and its alleviation, in wild populations.

The decisions and conditions of animals often carry over to influence fitness in subsequent seasons or years. The condition, choices, and behaviors of parents may have a huge influence on offspring survival, not only when they are nutritionally dependent (i.e., pre-weaning or pre-fledgling), but also after they have reached independence but before adulthood (i.e., post-weaning or post-fledgling). Using a long-lived, iteroparous mammal, we evaluated the hypothesis that carryover effects of a mother's condition (i.e., age and nutritional condition) and her behavior and decisions during the first few months of her offspring's life will influence survival of juvenile deer after they reach nutritional independence-during their first migration and their first winter. Age of a mother and mass of her neonates at birth influenced if her offspring survived their first winter; mothers who were young or had high body fat produced offspring that were more likely to survive winter. Moreover, mothers could improve overwinter survival of their offspring by delaying the initiation of their autumn migration. Internal characteristics (i.e., body fat and age) and decisions of parents during their offspring's first year of life carried over to influence survival of those juveniles after they become nutritionally independent. Juvenile animals still carry the costs and face the consequences of their mother's decisions well into the period of their independence. The influence of parental characteristics on offspring survival once independent demonstrates the importance of considering how environmental and behavioral characteristics influence survival across generations.

Nutrition is the foundation of life and yet, resources are finite. For wild animals, variation in resources and risk across time and space has resulted in a wide array of adaptations that allow individuals to meet daily metabolic and nutritional needs, including seasonal changes in metabolism, capital stores, and diverse reproductive strategies. For long-lived, iteroparous mammals, resources should be obtained, allocated, and stored in a way that balances current needs and yet, is sensitive to future requirements for survival. We propose that risk-sensitive allocation of energy is the mark of a nutritional legacy associated with an anticipatory adaptation of seasonal and variable environments. Here, we synthesize how nutritional legacies are interwoven into the very existence and life history of large ungulates, and how the accumulation of nutritional legacies across lifetimes and generations emerges into a nutritional ecotype. We describe nutritional ecotypes as the integrated profile of how large ungulates anticipate, acquire, store, and allocate energy across temporal scales, from daily decisions to evolutionary history. The annual fat cycle of ungulates, although affected by environmental conditions, is an anticipatory outcome of risk-sensitive allocation of resources anchored in metabolic programming within the context of a specific environment and the life history of a species or sex. Refinement in risk-sensitive allocation across days, seasons, lifetimes, and generations yields an important life-history adaptation that enables animals to align resource acquisition and allocation with the specific environments they occupy. Energetic strategies of wild animals are both a product of past experiences and the anticipation of the risks and resources that will occur in the future; the shaping of a nutritional ecotype in wild ungulates is itself an adaptation to local environments. We contend that further appreciation for nutritional ecotypes holds potential to advance our understanding of how large ungulates will persist or fail to, in our ever-changing world.

Mule deer (Odocoileus hemionus) are declining in abundance across their broad distribution in western North America. Identifying drivers of mule deer demography could inform habitat restoration. However, linking habitat quality to vital rates is challenging and often done indirectly using proxy metrics. We combine habitat selection with climate-related effects to identify synergistic influences affecting mule deer age ratios (fawn:doe). We used location data from 1473 female deer over 22 years in Wyoming to fit seasonal resource selection models, predict habitat suitability, and model age ratios as a function of drought conditions, winter severity, and seasonal habitat. Here we show temperature had the largest effect on mule deer recruitment with age ratios declining following hotter summers and colder winters. Age ratios increased with higher proportions of habitat with high-quality summer habitat of particular importance. Given the likely increases in summer temperatures and extreme winter weather events, populations may struggle to increase recruitment over the next half-century. Targeted management supporting forage quantity and quality, especially on summer range, could buffer the effects of decades-long drought conditions. Our findings also indicate mule deer avoid areas with high densities of oil and gas development. By delineating important mule deer habitat, we offer spatial tools for development siting and mitigation in Wyoming and a framework for broader application across the western United States.

Sustainable human–wildlife coexistence requires a mechanistic understanding of the many ways that humans affect animals. However, progress is hampered by the lack of accessible data measuring the dynamic presence of people. Here, we leverage mobile-device data to disentangle how human presence and landscape modification differentially influence the use of geographic and environmental space for 37 mammal and bird species across the United States. Human presence affected more than 65% of species, with substantial variation across species. For ~60% of species that responded to human activities, the effects were interdependent—animals tended to react more strongly to human presence in less modified habitats. Our results demonstrate that human presence and landscape modification have complex combined effects on wildlife, which need to be considered for effective management.

ABSTRACT Although translocations can be effective for augmenting and restoring wild populations, they can disrupt native patterns of genetic structure, diversity, and local adaptation, thereby hampering conservation efforts. Managers must weigh potential costs and benefits of choosing well‐differentiated donor individuals that could confer a boost to genetic diversity while avoiding outbreeding depression or ecological mismatch. This decision is more daunting when taxonomy is unclear or debated. For example, bighorn sheep (Ovis canadensis) populations in the United States that have been managed as the “California” lineage (part of the formerly recognized subspecies O. c. californiana) originate from serial translocations sourced from populations in British Columbia, resulting in reduced genetic diversity and elevated risk of inbreeding. After research on skull shape and RFLP analysis of mtDNA failed to find support for that subspecies, some jurisdictions treated the California lineage as part of the Rocky Mountain subspecies (O. c. canadensis) and mixed individuals in subsequent translocations, in part to increase genetic diversity of bottlenecked populations. Yet, detailed genetic data addressing validity of those putative lineages were lacking. We reconstructed the genetic history of bighorn sheep by sampling the major putative subspecies or lineages, focusing on native (remnant) genetic variation, and generating high‐throughput DNA sequencing data (~15,000–25,000 SNPs). Complementary phylogenetic and population genetic analyses supported the distinctiveness of four bighorn lineages at levels corresponding to subspecies. Our results confirm the genetic identity of the no longer putative California bighorn lineage, answering a question that puzzled geneticists and managers for decades. Moving forward, we recommend that managers (1) maintain the natural variation held in native populations by protecting them from intentional translocations or unintentional mixing with nearby populations; (2) prioritize within‐lineage translocations for population augmentation or repatriation to previously occupied regions; and (3) cautiously consider any translocations that would lead to mixing of distinct evolutionary lineages.

Conifer forests have experienced widespread disturbance following the infestation of bark beetles (Dendroctonus spp.). Tree mortality and resulting canopy loss have altered forest composition in ways that could affect moose (Alces alces), including potential benefits from increased understory forage and drawbacks through the loss of refuge from heat and deep snow. We examined the behavioral response of moose to beetle-killed forest, comparing resource selection before (2005-2006) and after (2015-2017) disturbance in southeast Wyoming, USA. To evaluate selection, we created a land cover classification layer at 0.5-m resolution using machine learning to delineate dead conifers, as well as aspen and willows that were underrepresented in existing land cover products. By measuring resource selection in a fractional cover framework, we found that moose showed strikingly similar resource selection before and after beetle disturbance. Moose during both periods selected willows and aspen while avoiding conifer forest and shrubs throughout the year. Moose in the post-beetle periods avoided conifer forest more strongly the more conifer forest made up their home range. The same pattern emerged for beetle-killed conifer: the more beetle-kill in a home range, the stronger the avoidance of beetle-kill. Our findings indicate that forest disturbance caused by bark beetles does not appreciably alter habitat quality for moose, and moose continue to employ similar patterns of resource selection regardless of forest changes in the early stages of the post-beetle infestation. Our work supports the importance of riparian and deciduous land cover in sustaining moose populations in the face of widespread forest disturbances.

Although migration is widespread among many animal taxa, including ungulates,1 the fitness benefits associated with different migratory tactics have rarely been documented.2,3 Here, we evaluated a 9-year dataset on a migratory population of mule deer in western North America to understand whether long-distance migration provides access to seasonal forage, which translates into demographic benefits. Mule deer that migrated over 50 km to high-elevation summer ranges accessed higher forage quality and thus gained around twice the amount of fat over the growing season compared with mule deer that remained year-round as residents within a desert ecosystem. Elevated levels of fat translated to ∼20% higher probability of adult annual survival than residents. Mule deer that remained year-round in the desert portion of the study area were so resource-limited that they raised fawns at the expense of their own survival. Due to their higher levels of fat, annual survival, and fetal rates, migrants showed more robust population growth (λ = 1.03) compared to residents, which exhibited projected declines in population size over time (λ = 0.95). These results support the notion that migration translates into demographic benefits and highlight the urgent conservation work necessary to sustain diverse ungulate migrations amid habitat alteration due to climate change and an expanding web of linear barriers to movement.3,4,5

Wildlife and their habitats face profound challenges from climate and landscape-scale changes that extend beyond the influence and time horizon of most biologists and land managers. In this changing environment, long-term datasets can enhance assessments of how demographic trends respond to interactions among local (e.g., habitat restoration decisions) and broad extent drivers, including energy development, to shape wildlife populations. Although many studies evaluate habitat selection or demographics for a single population, our multipopulation, multiscale study quantifies the influence of local management actions given broader environmental forces using both immediate and lagged effects. This approach may be particularly important for species with high site fidelity that may have less adaptive capacity, including mule deer (Odocoileus hemionus), which are experiencing widespread population declines. We analyzed a 40-year (1980-2019) dataset for 37 mule deer populations across Wyoming, USA, to test hypotheses about and quantify the relative influence of conditions within winter use areas on annual rates of juvenile recruitment. Recruitment has been strongly affected by multiple factors largely beyond the control of managers. Land cover (agriculture and shrubland) had the largest positive effects on recruitment, with estimates more than twice the magnitude of other variables, but also had limited presence in some winter use areas. The next strongest effect sizes were shared by energy developments (including oil/gas and wind energy) and climatic conditions, which, except for wind turbines, had broad distributions across winter use areas. Recruitment increased with higher mean winter temperatures and summer precipitation, but declined with wind, oil and gas developments, cumulative drought, and wildfire. Expected increases in drought and decreases in summer precipitation may constrain options to sustain mule deer populations. Although mule deer recruitment may sometimes be enhanced through habitat restoration, effects varied with treatment type, habitat type, and time since treatment. Given large constraining effects of temperature and drought, supporting drought resiliency for important habitat may be useful. Our results can be used to weigh the relative strength of threats and the value of restoration actions, interpret historic demographic change, prioritize populations for conservation, and optimize options for wildlife habitat management.

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

For nearly half a century, ecologists have sought to explain animal space use through characteristics of the environment (i.e., habitat). Recent evidence suggests animals also use memory of previous experiences to decide when and where to move. Yet, the relative influence of the two in explaining animal space use has not been resolved. Using six large ungulate species in the Rocky Mountains (USA), we evaluated the performance of a habitat selection model with 16 environmental variables and another with two variables representing previous use (i.e., memory). While memory outperformed the environment for two species and the environment outperformed memory for four species, the influence of memory and the environment was overall comparable. The environment best explained the space use of specialists, while memory best explained species with strong site fidelity. Our work challenges traditional habitat selection theory, showcasing that animals build their spatial preferences through experience just as much as merely responding to their environment.

Deterioration in nutritional condition with aging could reduce reproductive success but coincides with declines in residual reproductive potential, thus invoking opposing expectations for late-life reproduction. Yet, the mechanisms regulating energy accrual and allocation to reproduction and survival throughout the lifetime of long-lived, iteroparous animals have remained elusive owing to variation in energetic costs across their extended reproductive cycle (from conception to juvenile independence). Using 10 years of repeated measures of both nutrition (i.e., body fat and food availability) and reproductive allocation across the reproductive cycle of 232 free-ranging, adult, female mule deer, we revealed that nutrition is a critical piece in understanding patterns of reproductive senescence and terminal investment. From conception to weaning, age-related patterns of reproduction were influenced by both body fat and environmental conditions. Reproductive senescence was clear across the entire reproductive cycle, although allocation to offspring was partly mediated by nutrition. Terminal investment, however, was most evident towards the end of the annual reproductive cycle and unveiled only when considering nutritional condition and food availability; during years with poor resource availability, older mothers raised larger juveniles (i.e., 6-months old). Our work evokes nutrition as a lurking variable in end-of-life reproductive tactics for long-lived animals, while demonstrating the necessity of accounting for energy when considering patterns of reproductive senescence and terminal investment in wild animals.

Moose ( Alces alces ) are a cold-adapted species that may be vulnerable to overheating at relatively low temperatures in winter. Moose have two main strategies for thermal regulation: shifting activity patterns and selecting habitat that provides thermal refuge. In this study, we compared how moose use these two strategies in response to winter temperature across their latitudinal range. First, we used hidden Markov models to delineate encamped and traveling movement states for five populations of global positioning system-collared moose in relation to time of day, temperature, and snow depth. Next, we used step-selection functions to determine influential covariates of encamped locations. As air temperatures and snow depths increased, moose from all populations were more likely to remain in an encamped, relatively stationary state. All moose became less diurnal and more nocturnal at high temperatures, although the magnitude of changes in activity varied by population. Encamped northern moose selected shrubby habitat that presents foraging opportunities, whereas encamped southern moose selected for coniferous forest that provides poor forage but offers shade in southern regions. The only moose population to select for lower temperatures also experienced the warmest winter on record during our study period, which may explain this population’s low overall activity rates. Our results indicate that moose along their southern range extent are responding to elevated mid-winter temperatures by initially altering activity patterns and subsequently selecting for potential thermal refugia at the expense of foraging habitat, while northern moose were unlikely to shift habitat selection based on temperature unless faced with an anomalously warm winter. As climate change is implicated in range contraction and population declines, our findings suggest that high winter temperatures may be causing moose to not only reduce overall activity but also to forgo preferred foraging habitat in favor of prioritizing thermal refuge, thus forcing a trade-off between nutrition and thermoregulation.

For many migratory ungulates, cultural inheritance maintains migration through the social transmission of information between individuals, whereas learning and memory inform movement within individuals.1,2,3 It is often assumed, but rarely tested, that offspring inherit migratory routes by learning from their mothers.4,5 Here, we evaluate whether daughters inherit migratory routes from their mothers by following 16 mother-daughter pairs of mule deer (Odocoileus hemionus) from each daughter's first migration, through their yearling migration, and into adulthood. Adult routes for two-thirds of daughters overlapped with their mother's route, suggesting that they inherited migratory routes from their mothers. The adult routes for the remaining daughters, however, bore little or no similarity to their mother's routes, suggesting that these routes were instead shaped by individual experiences or non-maternal social interactions. Regardless of whether routes were inherited or not, the strategy that daughters used was influenced by their yearling migratory route, which underscores the importance of this period for establishing lifelong behaviors. For mule deer and other species where migration is informed by cultural inheritance, learning, and memory, the specific mechanisms that establish memory can have lifelong and cross-generational ramifications. Our work emphasizes the role of social information and early-life experiences in establishing and maintaining migratory behavior, raises new lines of inquiry about what underpins variation in migratory behavior, and points to potential strategies for the resilience of an often-imperiled behavior in a changing world. VIDEO ABSTRACT.

Natural selection favors species with strong fidelity to seasonal ranges where resources are predictable across space and time. Extreme disturbance events may negate the fitness benefits of faithfulness—with consequences for population distributions. We hypothesized that extreme events fragment population distributions through two mechanisms: (1) reductions in fidelity or (2) elevated mortality. We tested the relative contributions of these mechanisms to population dynamics of mule deer (Odocoileus hemionus)—a long-lived mammal—with long-term, individual-based information before and after disturbance occurred. We evaluated our hypotheses in response to disturbance during winter using a unique dataset of the movement and fate of adult females from a migratory population of mule deer over 8 years in western Wyoming, USA. First, we calculated fidelity of individuals between progressive winters and identified vacant space between population-level ranges to represent gaps in the population distribution. We then assessed: (1) how internal state and disturbance conditions affected fidelity, (2) how internal state, disturbance conditions, and fidelity affected survival, and (3) how survival and fidelity affected creation of gaps in population distribution. Disturbance weakened fidelity, but fidelity did not affect survival. Nutritional condition and age affected survival. Weakened fidelity did not change population distribution; rather, nutritional condition underpinned population dynamics, meaning that behavior alone may not prevent the creation of gaps in distribution following extreme disturbances. Extreme events may render behavioral plasticity incapable of mitigating mortality risk, and the environmental conditions that animals experience during the months, seasons, or even years before an event may regulate population-level organization in its aftermath.

Behavioural consistency and plasticity can both benefit fitness. Repeatability in behaviour within a specific context, termed temperament or trait-like behavioural responses, fosters adaptive responses to stimuli. Behavioural plasticity, on the other hand, enables state-like responses, aligning behaviour with internal and external conditions. The nutritional state of an organism significantly impacts behaviours and may interact with temperament. However, the specific contributions of trait- and state-like responses to stimuli remain poorly understood. Using a long-term data set on mule deer, Odocoileus hemionus, elk, Cervus canadensis, and bighorn sheep, Ovis canadensis, we assessed the interplay of temperament and nutritional state in behavioural responses during handling. We measured the repeatability of kick rates across multiple capture events over time, investigating its association with temperament, nutritional condition, age and capture frequency. Bighorn sheep and mule deer exhibited high repeatability in kicks during capture, while elk did not. State-dependent factors, such as body fat, minimally influenced kick rates during capture. In bighorn sheep and mule deer, trait-like responses were likely related to temperament, whereas elk demonstrated neither state- nor trait-like behavioural responses. Trait-like responses in these species may reflect adaptations to specific ecological niches and site-specific evolutionary pressures. Our findings advance our understanding of these mechanisms, shedding light on the complex interplay between temperament, nutritional state and behaviour. Nevertheless, our results highlight the need for caution when predicting or extrapolating behavioural responses to stressors across closely related species. (c) 2024 The Authors. Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).