Survival Of Deer Research Articles

A fine-scale examination of parturition timing in temperate ungulates.

Parturition timing has long been a topic of interest in ungulate research. However, few studies have examined parturition timing at fine scale (e.g., <1 day). Predator activity and environmental conditions can vary considerably with diel timing, which may result in selective pressure for parturition to occur during diel times that maximize the likelihood of neonate survival. We monitored parturition events and early-life survival of elk (Cervus canadensis) and mule deer (Odocoileus hemionus) in Utah, USA to better understand diel timing of parturition in temperate ungulates. Diel timing of parturition was moderately synchronous among conspecifics and influenced by environmental variables on the date of parturition. For elk, parturition events were most common during the morning crepuscular period and generally occurred later (i.e., closer to 12:00) when a relatively large proportion of the moon was illuminated. For mule deer, parturition events were most common during the diurnal period and generally occurred later (i.e., closer to 15:00) on cold, wet dates. Diel timing of parturition did not influence neonate survival, but larger datasets may be required to verify the apparent lack of influence. Although additional work could evaluate alternative variables that might affect parturition timing, our data provide an improved and finer scale understanding of reproductive ecology and phenology in ungulates.

White-tailed deer population dynamics in a multipredator landscape shaped by humans.

Large terrestrial mammals increasingly rely on human-modified landscapes as anthropogenic footprints expand. Land management activities such as timber harvest, agriculture, and roads can influence prey population dynamics by altering forage resources and predation risk via changes in habitat, but these effects are not well understood in regions with diverse and changing predator guilds. In northeastern Washington state, USA, white-tailed deer (Odocoileus virginianus) are vulnerable to multiple carnivores, including recently returned gray wolves (Canis lupus), within a highly human-modified landscape. To understand the factors governing predator-prey dynamics in a human context, we radio-collared 280 white-tailed deer, 33 bobcats (Lynx rufus), 50 cougars (Puma concolor), 28 coyotes (C. latrans), and 14 wolves between 2016 and 2021. We first estimated deer vital rates and used a stage-structured matrix model to estimate their population growth rate. During the study, we observed a stable to declining deer population (lambda = 0.97, 95% confidence interval: 0.88, 1.05), with 74% of Monte Carlo simulations indicating population decrease and 26% of simulations indicating population increase. We then fit Cox proportional hazard models to evaluate how predator exposure, use of human-modified landscapes, and winter severity influenced deer survival and used these relationships to evaluate impacts on overall population growth. We found that the population growth rate was dually influenced by a negative direct effect of apex predators and a positive effect of timber harvest and agricultural areas. Cougars had a stronger effect on deer population dynamics than wolves, and mesopredators had little influence on the deer population growth rate. Areas of recent timber harvest had 55% more forage biomass than older forests, but horizontal visibility did not differ, suggesting that timber harvest did not influence predation risk. Although proximity to roads did not affect the overall population growth rate, vehicle collisions caused a substantial proportion of deer mortalities, and reducing these collisions could be a win-win for deer and humans. The influence of apex predators and forage indicates a dual limitation by top-down and bottom-up factors in this highly human-modified system, suggesting that a reduction in apex predators would intensify density-dependent regulation of the deer population owing to limited forage availability.

Urbanization and primary productivity mediate the predator–prey relationship between deer and coyotes

AbstractPredator–prey interactions are important for regulating populations and structuring communities but are affected by many dynamic, complex factors across large scales, making them difficult to study. Integrated population models (IPMs) offer a potential solution to understanding predator–prey relationships by providing a framework for leveraging many different datasets and testing hypotheses about interactive factors. Here, we evaluate the coyote–deer (Canis latrans–Odocoileus virginianus) predator–prey relationship across the state of North Carolina (NC). Because both species have similar habitat requirements and may respond to human disturbance, we considered net primary productivity (NPP) and urbanization as key mediating factors. We estimated deer survival and fecundity by integrating camera trap, harvest, and biological and hunter observation datasets into a two‐stage, two‐sex Lefkovich population projection matrix. We allowed survival and fecundity to vary as functions of urbanization, NPP, and coyote density, and projected abundance forward to test eight hypothetical scenarios. We estimated initial average deer and coyote densities to be 11.83 (95% CI: 5.64, 20.80) and 0.46 (95% CI: 0.02, 1.45) individuals/km2, respectively. We found a negative, though highly uncertain, relationship between the current levels of coyote density and deer fecundity in most areas that became more negative under hypothetical conditions of lower NPP or higher urbanization, leading to lower projected deer abundances. Though not conclusive, our results indicate the possibility that coyotes could have stronger effects on deer populations in NC if their densities rise, but primarily in less productive and/or more suburban habitats. Our case study provides an example of how IPMs can be used to better understand the complex relationships between predator and prey under changing environmental conditions.

Moose and white‐tailed deer mortality peaks in fall and late winter

AbstractThe Grand Portage Band of Lake Superior Chippewa manages for sustainable subsistence harvests of moose (mooz; Alces alces) and white‐tailed deer (waawaashkeshi; Odocoileus virginianus). Moose populations in northern Minnesota, USA, are declining, which may necessitate alterations to Indigenous subsistence practices. Moose and deer exhibit seasonal behaviors such as altered space use and movement strategies, to which gray wolves (ma'iingan; Canis lupus) and humans may adapt, resulting in seasonal mortality patterns. Identifying periods of increased moose and deer vulnerability is important for achieving tribal conservation objectives. We assessed seasonal cause‐specific mortality of adult moose (2010–2021) and deer (2016–2022) fitted with global positioning system collars on and near the Grand Portage Indian Reservation (Gichi Onigaming; GPIR) in Minnesota and hypothesized mortality risk would be influenced by species‐specific space use patterns and weather. We estimated survival rates and mortality risk using time‐to‐event models. We recorded 42 moose mortalities (17 health issues, 8 predations, 4 subsistence harvests, 13 unknown causes) and 49 deer mortalities (26 predations, 13 harvests, 4 other causes, 6 unknown causes). Mean annual moose survival was 83.2%, and mortality risk peaked during late winter (~25 April) and fall (~8 October). Mean annual deer survival was 48.0%, and mortality risk peaked during late winter (~25 March) and during their fall migration period (~11 November). Mortality timing coincided with transitions between space use states (i.e., periods of spatial stability), suggesting ungulates are at greater risk during these transitional periods, though movement strategy (i.e., resident vs. migratory) did not influence mortality risk. Further, increased winter severity corresponded with increased deer mortality. We observed similar temporal peaks in mortality risk when harvest mortalities were censored, suggesting our observed seasonal mortality peaks occur naturally despite harvest comprising most fall deer mortality. Our results can inform population models and harvest regulations by identifying periods of mortality risk on GPIR under Anishinaabe principles of seventh‐generation conservation planning.

A PRELIMINARY INVESTIGATION OF PATHOGEN EXPOSURE OF ADULT FEMALE WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) AND SURVIVAL OF ASSOCIATED FAWNS IN THE WESTERN DAKOTAS, USA.

Exposure of a dam to pathogens may potentially affect her fawns positively or negatively. Mammalian females transfer immunologic protection to their offspring via colostrum obtained while nursing. Conversely, chronic diseases in dams may potentially result in small and weak neonates, reduced milk production or quality, or infection. Little is known about how pathogen exposure in adult female white-tailed deer (Odocoileus virginianus) affects offspring survival. Our objective was to assess pathogen exposure for female white-tailed deer and subsequent survival rates of fawns in Dunn and Grant counties, North Dakota, and Perkins County, South Dakota, USA. We collected blood serum from 150 adult female deer during 2014. We compared survival of 49 fawns to maternal exposure to 10 pathogens from 37 of 150 adult females. There was no difference in fawn mass between dams based on antibody status and no difference in fawn survival for nine pathogens. The 12-wk survival for fawns born to mothers with antibodies against bovine herpesvirus 1 (BoHV-1, causing infectious bovine rhinotracheitis) was lower than for fawns born from mothers without antibodies against BoHV-1; however, the indirect or direct impacts of BoHV-1 exposure in mothers on fawn survival are unclear. Although our findings suggest that the cost of exposure to previous diseases may have minimal impact on short-term fawn survival for most pathogens, additional research with increased sample sizes is needed to confirm our findings.

Effects of Anthropogenic and Climate-Induced Habitat Changes on Adult Female Mule Deer Survival

Increased wildfire size and frequency, invasion of non-native annual grasses, extensive fire suppression, climate change, and widespread juniper expansion have led to dramatic changes in sagebrush ecosystems, which provide habitat for a suite of wildlife species, including mule deer (Odocoileus hemionus). These landscape-level disturbances can cause habitat loss and degradation, which influence the quantity and quality of available forage and can negatively influence adult female mule deer survival. We used Program MARK to estimate survival rates using a known-fate model. Our dataset included 111 radio-collared female mule deer to estimate monthly survival rates and to investigate factors that may affect these rates, including movement behavior (migratory or resident) and habitat characteristics (wildfire and juniper canopy cover) in mule deer habitats supporting sagebrush potential vegetation types (PVTs). The dataset included 116 421 Global Positioning System (GPS) location points from 2015 to 2017 in the John Day Basin, Oregon, United States. Survival averaged 0.78 (95% confidence interval = 0.61–0.82) across the study period but was 0.69 (95% confidence interval = 0.59–0.77) in 2015. Our results indicated survival was positively influenced by the presence of small amounts of recent fire (< 15% of total winter range burned; 1−20 yr postfire) within an individual's winter range. Annual survival (0.78) was low compared with survival rates for adult female mule deer in other parts of their geographic range. These findings demonstrate how postfire vegetation response can have a positive effect on mule deer survival, regardless of their migration strategy. Our findings also indicate how climate change poses a growing threat to mule deer populations as prolonged periods of drought increase the spread of fatal diseases.

Outcomes associated with translocation of mule deer (Odocoileus hemionus): Influence of age, release timing, and year on survival

Translocation of large mammals has become common practice for wildlife managers charged with conservation of animals and their genetic integrity on increasingly modified landscapes. Translocations of ungulates have occurred around the world with varying outcomes. Although translocations have been used to manage mule deer (Odocoileus hemionus) in western North America, only recently have the outcomes associated with this management practice been documented. Our objective was to evaluate survival of translocated mule deer in comparison to resident mule deer over multiple years following release and provide information useful in judging the relative value of translocation as a conservation strategy for this species. In January and March 2013, the Utah Division of Wildlife Resources (UDWR) captured and translocated 102 mule deer from winter range near Parowan, Utah to winter range near Holden, Utah (approximately 145 kilometers north of capture location). We fitted each deer with a radio transmitter (n = 102 total: 21 GPS collars, 81 VHF collars) prior to release. We also captured and marked a total of 70 resident deer (9 GPS collars, 61 VHF collars) to serve as a reference group. Survival of translocated deer in the first year was similar among release dates in January (0.51; 95% CI = 0.40–0.63) and March (0.53; 95% CI = 0.40–0.66). Annual survival of translocated deer, however, was lower than survival of resident deer (0.83; 95% CI = 0.72–0.90) in the first year after release. During the second year following release, however, survival of translocated animals (0.85; 95% CI = 0.71–0.93) was not different from that of resident deer (0.80; 95% CI = 0.69–0.88). Additionally, age strongly influenced the survival of translocated deer; young deer (e.g., 1.5 year olds) were more than twice as likely as old deer (e.g., 7.5 year olds) to survive the initial year following translocation. These data highlight the need to monitor translocated animals for multiple years following release and suggest that wildlife managers should expect to see higher survival rates during the second year following translocation and higher survival rates in younger deer compared to older deer.

From conception to recruitment: Nutritional condition of the dam dictates the likelihood of success in a temperate ungulate

Maternal effects are the influence of maternal phenotype and the maternally-provided environment on the phenotype (i.e., expression of traits) of offspring. Frequently, maternal effects are manifest both before and after parturition. Pre-parturition effects are primarily direct allocation of energy to the offspring that is in utero. Post-parturition effects can include direct (e.g., nursing and defending offspring) and indirect (e.g., selection of habitat that is relatively safe or has high nutritional value) influences. While both direct and indirect effects are often discussed, there is a paucity of information on the relative importance of each type on offspring due to the difficulty in monitoring mothers prior to parturition and mother-offspring relationships after parturition in free-ranging animals. Our objective was to determine the importance of direct maternal effects on birth weight, growth rates, and survival of mule deer (Odocoileus hemionus) fawns from birth through the first 18 months of life. We determined the effect of nutritional condition of the dam (mother) on birth weight (pre-parturition direct effect). We also examined the post-parturition direct effect of dam nutritional condition on growth rates and survival of fawns. Direct maternal effects were evident both before and after parturition; dams in better nutritional condition produced offspring with greater mass at birth, higher rates of growth, and increased survival. Our findings demonstrate that maternal nutritional condition influences fawn health from gestation through recruitment. These links highlight the importance of considering direct maternal effects when examining population dynamics and reproductive success in long-lived mammals. Management plans for ungulates should include assessment of nutritional condition of adult females to maximize likelihood of effective conservation.

Both temporal and spatial aspects of predator management influence survival of a temperate ungulate through early life

Recent meta-analyses indicate that predator removal experiments result in marginal increases in prey abundance at best. However, most predator removal studies take place for less than the target prey’s generation time and lack a targeted spatial approach. Our objective was to determine how temporal and spatial aspects of predator control influenced neonate survival of a temperate ungulate. We conducted multiyear coyote (Canis latrans) removals using a crossover experimental design. We found that consecutive years of predator removal increased survival of neonate mule deer (Odocoileus hemionus) more than a single year of removal. We also found that removing coyotes from areas near fawn birth sites increased fawn survival, whereas removing coyotes from areas farther from birth sites did not influence fawn survival. Our results underscore the need for coyote removal programs to (1) employ removal efforts over consecutive years to maximize effectiveness, (2) conduct spatially explicit removal efforts targeting fawning habitat, and (3) occur when the likelihood of additive mortality is high and prey populations have the resources available to grow.

Shifting agriculture and a depleting aquifer: implications of row-crop farming on mule deer population performance

Context Conversion of native vegetation to cropland is one of the most widespread anthropogenic landscape alterations, particularly in the Great Plains region of the United States. Mule deer occur throughout the Great Plains; however, it is the south-eastern edge of their geographical distribution, and few populations coincide with dense cropland. The rapidly depleting Ogallala Aquifer supplies irrigation to row-crops throughout the region, which will likely shift towards dryland agricultural practices in the near future. Aims We sought to understand how cropland use influences morphology, body condition indices, reproductive output, and survival of free-ranging mule deer. Methods We accumulated a multi-year, longitudinal dataset of movement and morphology for 146 mule deer in the Texas Panhandle. We linked seasonal cropland use with observed morphology, body condition metrics, and reproductive output via linear mixed-effect modelling and assessed the influence of cropland on annual survival by using Cox proportional hazard models. Key results Mule deer that did not use cropland at any time during the year exhibited morphological and nutritional indices similar to those that did; except body-fat percentage being greater for mature (≥4-year-old) males that used cropland. Further, cropland use did not predict survival probability. Analyses of cropland use during seasons defined by life-stage showed context-dependent nutritional benefits. Use of cropland during winter following reproduction demonstrated an increase in young (≤3-year-old) male antler size and body mass and summer crop use increased body condition for all males. Female mule deer that utilised cropland before pregnancy had increased probability of successful reproduction, demonstrating a potential capital investment strategy in reproduction. Conclusions Cropland does not limit morphology or survival of mule deer; however, additive use of row-crops can provide a nutritional buffer and enhanced reproductive output for individuals that choose to utilise it. Implications Our study demonstrates important population-level interactions with the environment for a species near the extent of their geographical distribution. Conversion of row-crop farming from aquifer depletion or climate shifts may not diminish mule deer populations, but these changes may alter specific habitat-nutritional health relationships that can influence population performance and future conservation efforts.

Adult white‐tailed deer survival in hunted populations on public and private lands

AbstractEstimates of sex‐ and age‐specific survival are important for guiding population management decisions for white‐tailed deer (Odocoileus virginianus). However, differences in deer survival between public and private lands can exist and, if unaccounted for, may affect wildlife agencies' ability to effectively manage statewide and local deer populations. From 2014 to 2016, we radiocollared and monitored survival of 79 adult white‐tailed deer (141 deer‐years; 62 male, 79 female) on 2 public and 2 private properties in Alabama, USA. We assessed the effects of sex, age, and landownership type (i.e., public or private) on adult white‐tailed deer harvest and survival patterns using an information‐theoretic approach. Hunter harvest accounted for 77% of observed mortalities (n = 23/30), but harvest and survival rates varied by sex and age. Harvest and survival were similar between public and private property despite more restrictive hunting regulations for antlered deer on public areas. Similar harvest rates were likely due to self‐imposed, quality deer management (QDM) harvest strategies on private land that emulated the effects of a state‐mandated antler point restriction (APR) on public land. Our findings indicate survival rates of adult white‐tailed deer may be applicable across landownership types where state‐mandated harvest regulations with respect to males are more restrictive on public than private property, due to the popularity of QDM by private‐land deer hunters. However, where regulations are similar across landownership types (e.g., no state‐mandated APR), differences in harvest and survival rates may exist.

Effects of David Deer Grazing on Soil Bacterial and Fungal Communities in an Eastern Coastal Wetland of China

The grazing activity of animals has a significant role on the environmental modification of land. In the coastal wetlands of eastern China, long-term David deer (Elaphurus davidianus) grazing has caused the degradation of various ecological elements in the area. Still, few studies have been reported concerning the effects of David deer grazing on the soil microorganisms of their habitats. We analyzed the community structure of soil bacteria and fungi in an area of continuous annual grazing and another area without traces of David deer grazing so as to learn about the effects of deer grazing on the soil microbial community structure in a spatial instead of temporal way, in preparation for improving the environment for deer survival. David deer grazing drastically changed the physicochemical characteristics of the soil, accelerating the alkalinization process and inhibiting the buildup of nutrients. There were differences in the microbial community structure between the grazed and the control areas, with bacteria predominating. The control had a higher level of bacterial and fungal alpha-diversity than the grazed area. The makeup of the soil’s microbial community was also influenced, except for the dominant microbial at the phylum level. In addition to the establishment of numerous complex fungal functional types, David deer grazing increased the number of bacterial functional types linked to the carbon cycle. The impacts of soil pH and urease activity on bacterial and fungi populations were highlighted using the redundancy analysis. This study demonstrates that David deer grazing changes and complicates microbial functional kinds of composition, as well as modifies the composition of the soil’s microbial community, improving the soil nutrient cycling process, mainly the carbon element.

Influence of interspecific competition on mule deer birthing and rearing site selection

AbstractUngulates often alter behavior and space use in response to interspecific competition. Despite observable changes in behavior caused by competitive interactions, research describing the effects of competition on survival or growth is lacking. We used spatial modeling to determine if habitat use by female mule deer (Odocoileus hemionus) was affected by other ungulate species prior to, during, and after parturition. We conducted our study in the Book Cliffs region of eastern Utah, USA, during 2019 and 2020. We used resource selection function (RSF) analysis to model space use of 4 ungulate species that potentially competed with mule deer: bison (Bos bison), cattle, elk (Cervus canadensis), and feral horses. We incorporated RSF models for competing species into a random forest analysis to determine if space use by mule deer was influenced by these other ungulate species. We used survival and growth data from neonate mule deer to directly assess potential negative effects of other ungulates. Habitat use by elk was an important variable in predicting use locations of mule deer during birthing and rearing. The relationship was positive, suggesting interference competition was not occurring. Survival of neonate mule deer increased as the probability of use by elk increased (hazard ratio = 0.185 ± 0.497 [SE]). Further, probability of use by elk in rearing habitat had no influence on growth of neonate mule deer from birth to 6 months of age, suggesting that exploitative competition was not occurring.

Assessing migration strategies and cause specific mortality of adult female White-tailed Deer (&lt;i&gt;Odocoileus virginianus&lt;/i&gt;) in North Dakota, USA

Life-history characteristics of White-tailed Deer (Odocoileus virginianus) have been documented in areas of the Northern Great Plains, but limited information is available in grassland dominated regions. We documented migration strategy, home range use, and survival of adult female White-tailed Deer in central North Dakota. We monitored 62 radio-collared adult (&gt;1.5 year-old) female White-tailed Deer from February 2010 to December 2012. We documented 86 summer home ranges and classified deer as resident, migratory, or exhibiting a late season movement. Mean migration distance between non-overlapping summer and winter home ranges was 11.76 km (SE 0.86, n = 21). Mean late season movements were 20.69 km (SE 2.94, n = 7) and were likely the result of deer exhausting food resources throughout winter. We also developed five competing models that represented variation in survival among time periods (e.g., pre-hunt, hunt, and post-hunt in 2010 and 2011). Our top model indicated that survival (S) was similar between hunt 2010 and post-hunt 2011 periods but was lower (S = 0.82; SE 0.04, 95% CI 0.73–0.89) than the remaining time periods (S = 0.97; SE 0.01, 95% CI 0.93–0.99). Our results suggest that deer migration strategies and survival are likely influenced by a combination of winter severity and food availability. Mortalities attributed to hunter harvest were low during our study, which may indicate that increased recreational opportunities could be made available, even after severe winters.

Understanding environmental patterns of canid predation on white-tailed deer (Odocoileus virginianus)

The outcome of encounters between predators and prey affects predation rates and ultimately population dynamics. Determining how environmental features influence predation rates helps guide conservation and management efforts. We studied where gray wolves (Canis lupus Linnaeus, 1758) and coyotes (Canis latrans Say, 1823) killed white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) in northern Wisconsin, USA. We monitored 499 white-tailed deer for cause-specific mortality between 2011 and 2014 using VHF radio collars. We investigated the locations of 125 deer mortalities and determined that 63 were canid (wolf or coyote) kill sites. We analyzed spatial patterns of kill sites using resource selection functions in a model selection framework, incorporating environmental variables including vegetative cover, human development, snow depth, and water. We found no evidence that vegetative cover or human development affected predation risk; however, we did find that increasing snow depth resulted in increased relative predation risk. This finding is consistent with existing research on the influence of snow cover on white-tailed deer survival. Our results suggest that understanding the spatial and temporal patterns of white-tailed deer predation requires a better understanding of snow depth variation in space and time. As climate change scenarios predict changes in snowfall throughout the northern hemisphere, understanding the effect on predator–prey spatial dynamics will be important for management and conservation efforts.

A Microhistological Investigation of Winter Diets of White-Tailed Deer in Relict Eastern Hemlock Stands, Upper Peninsula of Michigan

To better understand winter foraging patterns of Odocoileus virginianus (White-tailed Deer) in the context of global change, we assessed foraging trends using microhistological analysis of fecal pellets from 2006–2018 across a network of monitoring plots in 39 relict Tsuga canadensis (Eastern Hemlock) stands in the western Upper Peninsula of Michigan. We found that deciduous browse comprised the majority of the diet, but conifer species were also eaten. During severe winters, Eastern Hemlock and Abies balsamea (Balsam Fir) were more prevalent in the diet, whereas in mild winters, Thuja occidentalis (Northern White Cedar) was more prevalent. Because Northern White Cedar comprises only a small amount of the forest community in these stands, deer were likely traveling beyond these winter yarding areas to forage. The relationship between conifer consumption and winter severity highlights the importance of energy conservation for winter survival of White-tailed Deer. More extreme winter weather is predicted with climate change, potentially prolonging confinement and limited forage availability, which is liable to alter energy budgets of deer, thus potentially altering population dynamics.

White‐Tailed Deer, Weather and Predation: a New Understanding of Winter Severity for Predicting Deer Mortality

ABSTRACTVariation in white‐tailed deer (Odocoileus virginianus) mortality during winter affects population growth in cold climates. Across the northern extent of their range, mortality increases with colder temperatures and snow. Few studies have examined the relationships between winter conditions and deer mortality, and no studies have concurrently studied this relationship for different ages of deer across multiple years and landscapes. We used recently developed cause‐specific mortality models to evaluate temporal and age‐class variation in deer mortality in farmland areas and compared to published results from forest areas in Wisconsin, USA, from 2011–2014. We then used temporally varying snow and temperature covariates to predict mortality trends using telemetry information from 860 deer. Cause‐specific mortality in the farmland varied by age and year, similar to results from previous research in the forest. Human‐related mortality was the leading cause of mortality in the farmland during most years and ranged from 4.3% to 10.3% for juveniles and 3.6% to 9.1% for adults from 2011–2014. Very little predation occurred in the farmland, and this differed from previous research in the forest where predation was the leading cause of mortality. During more severe winters (2013 and 2014), other mortality, usually associated with starvation, was the leading cause of mortality for juveniles in the farmland but not adults. In the forest, we found support for saturating effects of accumulated snow depth days &gt;30.5 cm and accumulated temperature days &gt;0°C on mortality. We also found support for the relationship of mortality with accumulated temperature days &gt;0°C in the farmland but no relationship with snow depth. Deer tolerate sustained cold temperatures, but the timing of winter to spring transition is more important for deer survival in both forested and agricultural areas. In the absence of empirical survival information, managers can use our model to predict annual winter effects on deer survival, which can provide improved inference compared to traditional winter severity indices. Our results suggest changes in predator abundance may have minor influence on overwinter survival compared to winter weather. Based on mortality estimates from previous research, the highest predation rates on juvenile deer in the forest occurred when wolf (Canis lupus) counts were lowest and when wolf abundance was highest, juvenile deer predation rates were lowest. © 2021 The Wildlife Society.

First record of chronic Fascioloides magna infection in roe deer (Capreolus capreolus).

Fascioloidosis is an allochthonous parasitic disease in Europe caused by the digenean trematode Fascioloides magna. The final hosts of F. magna in Europe are defined as definitive, aberrant and dead-end. Roe deer are aberrant hosts in which juvenile flukes permanently migrate through the liver parenchyma. Failure in pseudocysts formation leads to the death of both the host and the parasite. In this paper we present gross and histological findings of F. magna infection in 34 roe deer. The special emphasis is on the pseudocyst formation accompanied with new fluke's migratory channels observed in 7 animals, suggesting reinfection and prolonged survival of roe deer. No F. magna eggs were recovered from the faeces of the infected animals. These findings indicate that pseudocyst formation is essential for roe deer survival, but also point out the potential beginning of adaptation processes in roe deer, altering otherwise acute and fatal disease into a chronic one.

Estimating Abundance of Desert Mule Deer Using Fecal DNA–Based Capture-Recapture

Wildlife conservationists and managers often need to estimate abundance and demographic parameters to monitor the status of populations, and to ensure that these populations are meeting management goals. DNA capture-recapture surveys have become increasingly common in situations where physical surveys are consistently difficult or counts are small or variable. Desert mule deer (Odocoileus hemionus eremicus) inhabit rugged terrain, occur at low population densities, and demonstrate cryptic behaviors, making monitoring and assessing population status difficult. We assessed the effectiveness of a fecal DNA–based capture-recapture method for estimating abundance and survival of desert mule deer. We designed and implemented a fecal DNA sampling design focused at water sources during the dry season (June–July) of 2015–2017 in the Little Chuckwalla Mountains (study area ∼968 km2) located in the Sonoran Desert of southeastern California. We conducted 6, 5, and 4 surveys in 2015, 2016, and 2017, respectively. We used the capture-recapture data in the POPAN open-population model to estimate abundance and the Cormack–Jolly–Seber model to estimate annual survival. We detected 234, 193, and 211 unique individuals in 2015, 2016, and 2017, respectively. Over the 3-year study, population abundance estimates ranged from 386 in 2015 (95% CI, 264–509) to 301 in 2017 (95% CI, 260–342). Precision (i.e., coefficient of variation [CV]) of male and female abundance estimates ranged from 7% to 16%, and CV for males and females combined ranged from 5% to 15%. Annual apparent survival for females and males was 0.91 (95% CI, 0.59–0.98) and 0.71 (95% CI, 0.51–0.85), respectively. We concluded that fecal DNA–based capture-recapture is an effective method for estimating abundance and survival of desert mule deer. This approach could be expanded to encompass additional areas adjacent to our study site, with the potential to monitor the larger metapopulation of desert mule deer in the Sonoran Desert of California. More generally, DNA mark-recapture may be widely applicable to other species that congregate around water sources (or any required resource) during part of the year. Results from this study will be useful for developing population monitoring plans and for studies evaluating the effects of human development or environmental factors on desert mule deer and other desert ungulates.

Demographic performance of a large herbivore: effects of winter nutrition and weather

AbstractVariation among demographic rates for a population reflects the allocation of available energy by individuals to competing life‐history strategies. Species exhibiting slow‐paced life histories often prioritize energy allocation to adult survival over any single reproductive event, therefore maximizing future reproductive potential. Survival of adult female ungulates is generally high with little variability, whereas survival of young is lower and often highly variable. When adult survival is high with low variability, juvenile survival may have a proportionally greater effect on population growth or decline. Weather also may affect population dynamics directly by influencing survival of young or adults, or indirectly through changes in nutritional condition of adult females that influence population growth rates. We experimentally manipulated forage availability during winter, by supplementing native forage with high‐energy pelleted feed ad libitum, to a subset of a population of mule deer (Odocoileus hemionus) to understand the effects of winter nutrition on survival of adult females and their young born the subsequent summer. We evaluated the effects of winter nutrition, individual‐based parameters, and environmental covariates on survival of adult female mule deer from 2013 to 2018, and neonatal mule deer from 2014 to 2016. We documented a 26% decrease in annual survival of adult female mule deer in 2017 in response to increased snowpack during the preceding winter. Neonates born to females that receive enhanced nutrition during winter preceding parturition had higher survival to weaning (0.49, SE = 0.12), compared to neonates born to females that did not receive enhanced nutrition (0.29, SE = 0.07). We observed no effect of enhanced winter nutrition on survival of adult females. Our results suggested winter nutrition of maternal females may influence juvenile survival and demonstrates the importance of forage quality available to adult females during mid‐pregnancy. Although we were unable to detect an effect of winter forage on survival of adults, direct effects of deep winter snow resulted in lower survival of adult females. Low survival of adult females in our study population is indicative of a declining population.