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.

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/).

The sustainable use of wildlife is foundational to the success of the North American model of wildlife conservation. Harvest management often is shaped through both species biology and public desires. The long timespan it takes males of most ungulate species to reach peak weapon size has created a situation in harvest management in which harvest strategies cannot prioritize both generous hunter opportunity and opportunities to pursue large-weaponed males; therefore, current harvest paradigms prioritize one at the expense of the other. In contrast to other species, pronghorn (Antilocapra americana) attain the majority of their peak horn size early in life. The rapid development of horns relative to their age may allow for liberal harvest without sacrificing the opportunity for hunters to harvest males with large horns. We evaluated the influence of sex ratios and average age of harvested males on the average horn size of harvested male pronghorn from 2019 to 2022 in 9 hunt areas in Wyoming, USA. Although mean age of harvested males was negatively affected by rate of harvest, increases in mean age at harvest led to only slight increases in mean horn size (i.e., a 1-year increase in mean age increased mean horn size by 2.1 cm [similar to 1 inch]). The proportion of the harvest composed of large-horned males was not influenced by mean age of harvest or sex ratio of the population. Based on simulated populations, increasing harvest led to an increase in the number of large-weaponed pronghorn in the harvest-a relationship that existed for bighorn sheep (Ovis canadensis) and elk (Cervus canadensis) but only at low to moderate rates of harvest. The comparatively young age that pronghorn attain near-peak horn size alleviates what is otherwise a tradeoff between hunter opportunity and managing for large horn size that is evident in management of other ungulate species. Though rarely a reality in management for large ungulates, for pronghorn, liberal harvest may be possible while still providing opportunity to harvest males with large horns.

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.

In North America, most ungulate species exhibit life-history traits typical of long-lived, iteroparous species wherein young males tend to prioritize essential life functions including body growth and maintenance that constrains allocation of resources to horn, antler, and pronghorn growth. As a result, males of most ungulate species require several years of growth before reaching asymptotic body size and thereafter, peak weapon size is attained. Unique among ungulate species in North America, pronghorn possess a suite of life-history traits resulting in a precocious (i.e., unusually early development) pace of life relative to other North American ungulates. We tested the hypothesis that the fast pace of life of pronghorn extends to precocious development of large horns, and evaluated how horn size was affected by environmental conditions during the year they were grown and the potential for cohort effects associated with environmental signatures during the year of birth. We evaluated the influence of age and the environment on horn size of pronghorn using data collected from 1,789 male pronghorn harvested from 2019 to 2022 in Wyoming, USA. Pronghorn attained 95% of their peak horn size by 3.5 years old. Climatic conditions influenced horn growth through cohort effects and year of growth pathways. Snow depth during the year of birth positively influenced horn size, whereas the effects of environmental conditions during the year of horn growth were dependent on age. For young animals, snow depth and moderate drought positively influenced horn size during the year of horn growth, but the effect was negligible for prime aged and old animals. The precocious nature of pronghorn extended to their horn growth characteristics, resulting in early attainment of a large proportion of their peak horn size. The unique ecology of pronghorn and rapid attainment of size early in life can allow for greater flexibility to balance hunter opportunity and production of large-horned males for pronghorn as compared with other ungulates.

For species that inhabit environments where resource availability may be unpredictable, balance of resource allocation to life‐history traits can have heightened consequences for survival, reproduction, and ultimately, fitness. Acquisition and allocation of energy to maintenance, capital gain and reproduction should be in tune with the landscape an animal inhabits—environmental severity, food availability and population size all influence the resources animals have and dictate the ways they should be allocated. In seasonal environments, animals that experience periods of extreme resource limitation (e.g. harsh winters) may favour allocation of resources to body reserves to secure their survival at the cost of reproduction (i.e. risk averse). In contrast, the same accumulation of body reserves may not be necessary to survive in relatively benign landscapes where instead, allocation to reproduction is favoured (i.e. risk prone). According to the theory of risk‐sensitive allocation of resources, when animals are exposed to unprecedented or life‐threatening conditions, they may shift resource allocation to favour building capital over allocation in reproduction to preempt against encountering another life‐threatening event in the future. Using data from a long‐term project on a highly site‐faithful and long‐lived species, mule deer ( Odocoileus hemionus ), we evaluated how a life‐threatening winter and the associated changes in resource availability resulting from a population reduction influenced how animals acquired and allocated energy to survival (i.e. fat accumulation). Per capita precipitation, and the associated reduction in population abundance after the severe winter, had a positive influence of accrual of fat over summer. After the extreme physiological stress of a hard winter, deer starting spring with low body reserves accumulated 2.8 percentage points more fat over summer compared with before the experience of a bad winter and had an increased probability of recruiting fewer offspring. Fat stores can interact with environment, life history and behaviour to influence survival during periods of resource scarcity. For a long‐lived herbivore, we documented shifts in risk tolerance associated with fat accrual in preparation for winter, supporting the notion that risk‐sensitive allocation of resources may be plastic—an essential adaptation for animals to cope with rapidly changing landscapes. Read the free Plain Language Summary for this article on the Journal blog.

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.

The authors declare no conflict of interest. Data on nutritional condition (Ortega et al., 2022) are available in Dryad at https://doi.org/10.5061/dryad.j3tx95xjs.

The nutrition of wild animals affects their ability to survive, reproduce, and ultimately persist in unpredictable environments. Nutrition interacts with the life history of animals across different scales (Smiley, LaSharr, et al., 2022), from long-term and cross-generational effects that dictate phenotype and reproductive success (Michel et al., 2016), to influences of their current environment on survival (Parker et al., 2009). For large mammals, nutrition underpins much of what they do. Particularly in temperate environments with harsh conditions and severe limitation of resources for extended periods, animals rely heavily on energy stored as fat during winter when resources are scarce (Mautz, 1978; Parker et al., 2009). In seasonal environments, the pattern of fat accumulation and depletion is closely synchronized to their environment and availability of resources (Smiley, Wagler, et al., 2022). Nevertheless, to survive when severe environmental conditions result in an unanticipated but necessary depletion in fat reserves, animals that persist are faced with severe consequences for reproduction that can span years or even generations. The environmental, physiological, and nutritional state of a mother has a lifetime effect on her offspring (Bernardo, 1996), and for ungulates, the nutrition of the mother during gestation can have an important and often underappreciated effect on the lifetime phenotype, behavior, and success of her offspring (Michel et al., 2016). The link between maternal nutrition and offspring performance may have important consequences for how populations or species respond to changing environments. Research in captive settings has shown, even with animals that are closely related (i.e., have similar genetic makeups), maternal condition can have serious lifetime implications for an animal's offspring; mothers in poor condition give birth to sons that exhibit stunted growth compared with sons born to mothers in good condition (Monteith et al., 2009). Yet, identifying the role of maternal effects in wild animals can be difficult. It requires information on the nutritional legacy of a mother in combination with information on current environmental conditions (Benton et al., 2001). Garnering data necessary to disentangle the effects of current nutritional state, environment, and maternal effects requires repeated sampling of mothers and their offspring through time. Long-term, individual-based research is expensive, and logistically challenging, but can provide intricate data to test complex questions and theories. Through a long-term research project, we observed how the nutritional legacy of a harsh winter before an animal's birth potentially influenced the growth and development of a male mule deer (Odocoileus hemionus) born in the wild. As part of a research project that was focused on disentangling the mechanisms of population performance of mule deer, in December 2013 in Wyoming, USA, we captured 70 adult females and fitted them with GPS collars (ATS, Iridium and Vectronic Aerospace, Vertex Plus). Each spring and autumn following that initial capture until December 2021, we recaptured each individual. From 2015 to 2021, we captured newborns of collared females and fit them with expandable VHF or GPS collars (ATS and Vectronic Aerospace). We recaptured all surviving juveniles (both males and females) as adults each spring and autumn following their survival to adulthood. At each capture event for adults, we measured nutritional condition (i.e., percent body fat) and each spring we measured pregnancy and fetal rates of female deer via ultrasonography (see Aikens et al., 2021 for detailed methodology). At each autumn capture, we measured antler size of male deer using standard approaches including measurements of beam lengths, tine lengths, and antler circumferences (Monteith et al., 2014). This long-term, individual-based study has allowed us to begin to elucidate the cross-generational roles of nutrition in a wild population. Mule deer in this population inhabit the Salt and Wyoming Ranges of Wyoming, and each year migrate from low-elevation (~1800 m) winter ranges dominated by sagebrush steppe to high-elevation (~2300–27,500 m) summer ranges, comprised of tall forb, mixed-mountain shrub, aspen, and conifer communities. Peak parturition occurred in mid-June, after migration to summer ranges (Aikens et al., 2021). Overwinter survival was heavily dependent on stored fat accumulated over summer, and winter conditions could be harsh. To assess how winter weather influenced the nutrition of a female mule deer and the subsequent fitness of her offspring, we evaluated the condition of a collared deer (deer 096) and her collared, male offspring (deer MFFO) born after a severe winter and the next 4.5 years of his life. During the winter of 2016–2017, animals in this population encountered harsher conditions than they had experienced in nearly 30 years (snowfall that winter was 236.2 cm, the third greatest annual snowfall recorded for the state; Smiley, LaSharr, et al., 2022), with prolonged periods of subzero temperatures and more extreme snow conditions than average. Indeed, average body fat of animals when captured between 8 March and 10 March 2017 was 2.3% (average during normal winters 4.6%), and although deer 096 (7 years old) was in better shape than many of her counterparts with 4.1% body fat (Figure 1), this population faced an additional 2 months of extremely harsh winter conditions. Animals were pushed to their physiological limits and many succumbed to overwinter mortality; survival of collared females was 70% and survival of collared juveniles (<1 year old) was 0%. After this particularly harsh winter, survival of offspring born in the spring of 2017 was low: 29% of juvenile mule deer born that summer were stillborn or succumbed to malnutrition early (stillbirth/malnutrition ranged from 3% to 18% in other years), further exemplifying the nutritional stress experienced by female deer. On 1 June 2017, deer 096 gave birth to two offspring, one male (MFFO) and one female. Despite the harsh winter that depleted the majority of fat reserves of animals in this population, deer 096 carried two fetuses to term and was successful in her reproductive efforts, likely a product of her higher than average fat levels for the population in spring of 2017. Recruitment of two offspring was something that was not achieved by most mule deer during that summer. Indeed, MFFO was the only male from his cohort that we had collared as an adult; despite capture efforts of random, adult males on the landscape we have not captured a male born during the summer of 2017 on MFFO's winter range. Yet, despite deer 096's success in recruiting two offspring into the population, the legacy of the harsh winter that preceded his birth probably followed MFFO for the remainder of his life. Over the 4.5 years that followed his birth, we recaptured him at 2.5 and 3.5 years of age and measured his antlers and nutritional condition; additionally when he was harvested as a 4.5 year old, we measured his antlers following harvest. MFFO never achieved antler growth that was comparable with average males in his age class in the population (Figure 2). Indeed, each year his antlers appeared more similar to the age class below him than to his actual age class. Compared with other males in this population, MFFO's antlers were 30% smaller than the average 2.5 year old, 33% smaller than the average 3.5 year old, and 20% smaller than the average 4.5 year old in each respective year of his life (Figure 3). Moreover, the amount of fat he had in the autumn was often similar or higher (7% and 9.7% at 2.5 and 3.5 years of age, respectively), compared with other mature males (i.e., 6.4%). Even though his nutritional condition demonstrated that he had access to high-quality food, he was probably unable to achieve his full phenotypic potential. Although there is the potential that expression of genetic potential for antler size was below average for MFFO, we suspect his stunted trajectory of antler growth was in large part a response to his mother's condition when he was in utero and a consequence of a life-lasting maternal effect on growth. The effect of maternal condition on offspring phenotype has been investigated using an individual-based approach in captive settings (Michel et al., 2016; Monteith et al., 2009), and has been evaluated at the population level in wild systems (Monteith et al., 2017). Yet, an investigation of maternal condition on offspring using an individual-based approach has yet to be achieved in wild populations. Long-term, individual-based research provides the opportunity to better understand wild populations and the mechanisms that drive their trajectories. Although MFFO is only a single individual, his striking growth pattern and size may well be driven by the lasting, deleterious effects of the 2016–2017 winter. Moreover, the trajectory of MFFO's growth and the connection to extreme environmental conditions and maternal nutrition has provided a unique opportunity to communicate complex concepts of nutrition and maternal effects to nonscientific audiences. There is an inherent value in the connection to individual animals that accompanies individual-based, long-term research; it can provide tangible examples that allow scientists to demonstrate intricate ecological theory to the public in an understandable manner (Jakopak et al., 2019). Storytelling is an effective and engaging way to allow nonscientific audiences to process, understand, and retain scientific information (Joubert et al., 2019). The story of MFFO's life and growth provides an example of the potential lifetime consequences that a mother's nutrition might have for her offspring in a wild population, regardless of the short-term environments and resources they experience. As populations of large herbivores are exposed to increasingly extreme conditions, changes to nutrition might have unanticipated consequences for animal phenotypes. We thank B. Wagler, R. Smiley, E. Moberg, E. Monfort, and T. Faber for assistance with data collection on the Wyoming Range Mule Deer project during the summer of 2017. The Wyoming Range Mule Deer study was supported by the Wyoming Game and Fish Department, Wyoming Game and Fish Commission, Bureau of Land Management, Muley Fanatic Foundation (including Southwest, Kemmerer, Upper Green, and Blue Ridge Chapters), Boone and Crockett Club, Wyoming Wildlife and Natural Resources Trust, Knobloch Family Foundation, Wyoming Animal Damage Management Board, Wyoming Governor's Big Game License Coalition, Bowhunters of Wyoming, Wyoming Outfitters and Guides Association, Pope and Young Club, the United States Forest Service, and United States Fish and Wildlife Service. We thank the multiple landowners that kindly offered access to their property for this research. The authors declare no conflict of interest. Nutritional condition data (LaSharr, 2022) are available in Dryad at https://doi.org/10.5061/dryad.0rxwdbs3b.

Every aspect of the life of a black-tailed and mule deer is ultimately fueled and made possible by the nutrition they gain from their foods, which is correspondent with everything from the size and shape of their muzzle to the microflora that reside in their digestive system. Black-tailed and mule deer persist on a diverse diet of plants, most of which are shrubs and forbs that yield digestible energy and protein at levels sufficiently high to support maintenance, growth, and reproduction. Allocation of acquired resources is sensitive to the nutritional state of the animal, which is best represented by percent body fat. Through state-dependent regulation of body reserves, black-tailed and mule deer are highly fecund, most frequently pregnant with twins, and subsequently support rearing of offspring through food intake and catabolism of somatic reserves if available. Integration of measures of animal nutrition into studies of population dynamics has led to major advances in understanding population ecology of black-tailed and mule deer. We anticipate continued advances into the future along with opportunities to better communicate to a diverse public and stakeholders the nuances of the ecology and nutritional underpinnings of this highly revered species.

For many species, behavioral modification is an effective strategy to mitigate negative effects of harsh and unpredictable environmental conditions. When behavioral modifications are not sufficient to mitigate extreme environmental conditions, intrinsic factors may be the primary determinant of survival. We investigated how movement behavior, and internal (i.e., nutrition and age) and external (i.e., food availability and snow depth) states affect survival over winter of a long-lived and highly faithful species (mule deer; Odocoileus hemionus). We first tested whether animals changed their behavior during winter based on internal and external states; we subsequently investigated how behavior and state interacted to influence survival in the face of extraordinary winter conditions. Movement behavior changed minimally as a function of age and nutrition; yet, movement behavior affected survival-animals that exhibited more restricted movements were more likely to succumb to mortality overwinter than animals with less restricted movements. Additionally, nutrition and cumulative snow depth had a strong effect on survival: animals that were exposed to deep snow and began winter with low fat were much less likely to survive. Behavior was an effective tool in securing survival during mild or moderate winters, but nutrition ultimately underpinned survival during harsh winters.

Capture and handling techniques for individual-based, long-term research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture-related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net-gunning to compare daily survival probabilities within a 10-week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from capture efforts was 1.59%. Mean daily survival was 0.9993 +/- 0.0001 (SE) during the 5-week pre-capture window, was depressed the day of capture at 0.9841 +/- 0.0004, and rebounded to 0.9990 +/- 0.0008 during the 5-week post-capture window. Neither capture nor handling had a detectable effect on post-capture survival, including handling time (x over bar $\bar{x}$ = 13.30 +/- 1.87 min), capture time of year (i.e., Dec or Mar), tooth extraction, and the number of times an animal had been recaptured (2-17 times). Although mortality rate was slightly elevated during capture (resulting from physical trauma associated with capture), age and nutritional condition did not influence the probability of mortality during a capture event. Following a capture event, nutritional condition influenced survival; however, that relationship was consistent with expected effects of nutritional condition on winter survival and independent of capture and handling. Overall survival rates 5 weeks before capture and 5 weeks after capture were not different. A specified window of time with depressed survival following capture and handling was not evident, which contradicts the implementation of a predetermined window often used by researchers and managers for censoring mortalities that occur after capture. Previous notions that censorship of all mortality data in the 2 weeks following capture is unwarranted and risks removal of meaningful data. With previous evidence guiding our protocols for capture (e.g., reduced chase time) and handling (e.g., temperature mitigation), low direct mortality and almost undetectable indirect mortality post capture reinforces the efficacy of helicopter net-gunning for capture and recapture of mule deer in long-term, individual-based studies.

The temporal windows during which animals complete essential life processes (i.e. temporal niche) allow animals to match their actions to a given environmental context. When completing seasonal migrations, some migrants switch their activity patterns (e.g. from diurnal to nocturnal in multiple species of migratory birds) to take advantage of better conditions. We tested the temporal niche -switch hypothesis by comparing activity patterns before and during migration for four populations of migratory mule deer, Odocoileus hemionus, in western Wyoming, U.S.A. (2007-2019). We predicted that the physically taxing and risky event of terrestrial migration would prompt shifts in diel activity patterns. In contrast to the niche-switch hypothesis, mule deer did not drastically change their activity patterns during migration. Both before and during migration, mule deer were crepuscular (i.e. most active during twilight hours). When migrating in the spring, however, mule deer tended to concentrate activity near dawn, although they did not concentrate activity near dawn in the autumn, when less snow was present. By moving in the morning during spring migration, mule deer moved when snow was hardest, potentially allowing them to avoid the energetic costs of sinking into deep snow. Mule deer overall maintained a consistent pattern of crepuscular activity, but fine-tuned their activity patterns during migration, which may allow them to better match their behaviours with environ-mental conditions while completing an important life event. Rather than abandoning activity patterns, animals instead may make subtle alterations in their activity patterns to take advantage of present conditions.(c) 2022 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Secondary sexual traits (e.g., horns and antlers) have ecological and evolutionary importance and are of management interest for game species. Yet, how these traits respond to emerging threats like infectious disease remains underexplored. Infectious pneumonia threatens bighorn sheep (Ovis canadensis) populations across North America and we hypothesized it may also reduce horn growth in male sheep. We assess the effect of pneumonia on horn size in male bighorn sheep using 12 herd datasets from across the western United States that had horn growth and disease data. Disease resulted in 12-35% reduction in increment (yearly) length and 3-13% reduction in total horn length in exposed individuals. The disease effect was prolonged when pathogens continued to circulate in sheep populations. Further, disease likely delays the age at which horns reach 3/4-curl and prevents achievement of full-curl. This is further evidenced with 6 of the 12 herds experiencing an increase in average age at harvest following die-off events.

Food quality and availability, when combined with energetic demands in seasonal environments, shape resource acquisition and allocation by animals and hold consequences for life-history strategies. In long-lived species with extensive maternal care, regulation of somatic reserves of energy and protein can occur in a risk-sensitive manner, wherein resources are preferentially allocated to support survival at the cost of investment in reproduction. We investigated how Rocky Mountain bighorn sheep (Ovis canadensis), an alpine mammal in a highly seasonal environment, allocates somatic reserves across seasons. In accordance with the hypothesis of risk-sensitive resource allocation, we expected accretion and catabolism of somatic reserves to be regulated relative to preseason nutritional state, reproductive state, and variation among populations in accordance with local environmental conditions. To test that hypothesis, we monitored seasonal changes in percent ingesta-free body fat (IFBFat) and ingesta-free, fat-free body mass (IFFFBMass) in three populations of bighorn sheep in northwest Wyoming between 2015 and 2019 through repeated captures of female sheep in December and March of each year in a longitudinal study design. Regulation of somatic reserves was risk-sensitive and varied relative to the amount of somatic reserves an animal had at the beginning of the season. Regulation of fat reserves was sensitive to reproductive state and differed by population, particularly over the summer. In one population with low rates of recruitment of young, sheep that recruited offspring lost fat over the summer in contrast to the other two populations where sheep that recruited gained fat. And yet, all populations exhibited similar changes in fat catabolism and risk sensitivity over winter. The magnitude of body fat and mass change across seasons may be indicative of sufficiency of seasonal ranges to meet energetic demands of survival and reproduction. Risk-sensitive allocation of resources was pervasive, suggesting nutritional underpinnings are foundational to behavior, vital rates, and, ultimately, population dynamics. For species living in alpine environments, risk-sensitive resource allocation may be essential to balance investment in reproduction with ensuring survival.

Nutrition underpins survival and reproduction in animal populations; reliable nutritional biomarkers are therefore requisites to understanding environmental drivers of population dynamics. Biomarkers vary in scope of inference and sensitivity, making it important to know what and when to measure to properly quantify biological responses. We evaluated the repeatability of three nutritional biomarkers in a large, iteroparous mammal to evaluate the level of intrinsic and extrinsic contributions to those traits. During a long-term, individual-based study in a highly variable environment, we measured body fat, body mass, and lean mass of mule deer (Odocoileus hemionus) each autumn and spring. Lean mass was the most repeatable biomarker (0.72 autumn; 0.61 spring), followed by body mass (0.64 autumn; 0.53 spring), and then body fat (0.22 autumn; 0.01 spring). High repeatability in body and lean mass likely reflects primary structural composition, which is conserved across seasons. Low repeatability of body fat supports that it is the primary labile source of energy that is largely a product of environmental contributions of the previous season. Based on the disparate levels in repeatability among nutritional biomarkers, we contend that body and lean mass are better indicators of nutritional legacies (e.g., maternal effects), whereas body fat is a direct and sensitive reflection of recent nutritional gains and losses.

Adenovirus hemorrhagic disease affects primarily mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), Rocky Mountain elk (Cervus canadensis nelsoni), and moose (Alces alces) in their first year of life. The method by which the causative virus, Deer atadenovirus A, is maintained in the environment and transmitted to neonates is unknown. In this study, we investigated the potential transmission of the virus from dam to offspring in Rocky Mountain mule deer (Odocoileus hemionus hemionus) and elk in western Wyoming, US. We sampled dams before parturition during placement of vaginal implant transmitters and at parturition and sampled neonates during capture in their first days of life. We also tested for the virus in mortalities submitted for pathologic examination and laboratory analysis. We detected viral DNA in samples from all time points tested but did not find a connection between positive dams and offspring mortalities associated with adenovirus hemorrhagic disease. Although we did not find direct evidence of transmission events between dams and offspring, asymptomatic animals shedding of Deer atadenovirus A, are a likely source of infection in neonates.

AbstractBirth timing is a key life‐history characteristic that influences fitness and population performance. For migratory animals, however, appropriately timing birth on one seasonal range may be constrained by events occurring during other parts of the migratory cycle. We investigated how the use of capital and income resources may facilitate flexibility in reproductive phenology of migratory mule deer in western Wyoming, USA, over a 5‐yr period (2015–2019). Specifically, we examined how seasonal interactions affected three interrelated life‐history characteristics: fetal development, birth mass, and birth timing. Females in good nutritional condition at the onset of winter and those that migrated short distances had more developed fetuses (measured as fetal eye diameter in March). Variation in parturition date was explained largely by fetal development; however, there were up to 16 d of plasticity in expected birth date. Plasticity in expected birth date was shaped by income resources in the form of exposure to spring green‐up. Although individuals that experienced greater exposure to spring green‐up were able to advance expected birth date, being born early or late with respect to fetal development had no effect on birth mass of offspring. Furthermore, we investigated the trade‐offs migrating mule deer face by evaluating support for existing theory that predicts that births should be matched to local peaks in resource availability at the birth site. In contrast to this prediction, only long‐distance migrants that paced migration with the flush of spring green‐up, giving birth shortly after ending migration, were able to match birth with spring green‐up. Shorter‐distance migrants completed migration sooner and gave birth earlier, seemingly trading off more time for offspring to grow and develop over greater access to resources. Thus, movement tactic had profound downstream effects on birth timing. These findings highlight a need to reconsider classical theory on optimal birth timing, which has focused solely on conditions at the birth site.

ABSTRACTInformation garnered from the capture and handling of free‐ranging animals helps advance understanding of wildlife ecology and can aid in decisions on wildlife management. Unfortunately, animals may experience increased levels of stress, injuries, and death resulting from captures (e.g., exertional myopathy, trauma). Partial sedation is a technique proposed to alleviate stress in animals during capture, yet efficacy of partial sedation for reducing stress and promoting survival post‐capture remains unclear. We evaluated the effects of partial sedation on physiological, biochemical, and behavioral indicators of acute stress and probability of survival post‐capture for mule deer (Odocoileus hemionus) that were captured via helicopter net‐gunning in the eastern Greater Yellowstone Ecosystem, Wyoming, USA. We administered 10–30 mg of midazolam and 15 mg of azaperone intramuscularly (IM) to 32 mule deer in 2016 and 53 mule deer in 2017, and maintained a control group (captured but not sedated) of 38 mule deer in 2016 and 54 mule deer in 2017. To evaluate indicators of acute stress, we measured heart rate, blood‐oxygen saturation, body temperature, respiration rate, and levels of serum cortisol. We recorded number of kicks and vocalizations of deer during handling and evaluated behavior during release. We also measured levels of fecal glucocorticoids as an indicator of baseline stress. Midazolam and azaperone did not reduce physiological, biochemical, or behavioral indicators of acute stress or influence probability of survival post‐capture. Mule deer that were administered midazolam and azaperone, however, were more likely to hesitate, stumble or fall, and walk during release compared with individuals in the control group, which were more likely to trot, stot, or run without stumbling or falling. Our findings suggest that midazolam (10–30 mg IM) and azaperone (15 mg IM) may not yield physiological or demographic benefits for captured mule deer as previously assumed and may pose adverse effects that can complicate safety for captured animals, including drug‐induced lethargy. Although we failed to find efficacy of midazolam and azaperone as a method for reducing stress in captured mule deer, the efficacy of midazolam and azaperone or other combinations of partial sedatives in reducing stress may depend on the dose of tranquilizer, study animal, capture setting, and how stress is defined. © 2020 The Wildlife Society.