Deer Mortality Research Articles

Effect of Enhanced Nutrition on Mule Deer Population Rate of Change

Abstract Concerns over declining mule deer (Odocoileus hemionus) populations during the 1990s prompted research efforts to identify and understand key limiting factors of deer. Similar to past deer declines, a top priority of state wildlife agencies was to evaluate the relative importance of habitat and predation. We therefore evaluated the effect of enhanced nutrition of deer during winter and spring on fecundity and survival rates using a life table response experiment involving free-ranging mule deer on the Uncompahgre Plateau in southwest Colorado, USA. The treatment represented an instantaneous increase in nutritional carrying capacity of a pinyon (Pinus edulis)−Utah juniper (Juniperus osteosperma) winter range and was intended to simulate optimum habitat quality. Prior studies on the Uncompahgre Plateau indicated predation and disease were the most common proximate causes of deer mortality. By manipulating nutrition and leaving natural predation unaltered, we determined whether habitat quality was u...

Early Mortality of Sika Deer,Cervus nippon, on Kinkazan Island, Northern Japan

Early Mortality of Sika Deer,<i>Cervus nippon</i>, on Kinkazan Island, Northern Japan

Ocular Plague (Yersinia pestis) in Mule Deer (Odocoileus hemionus) from Wyoming and Oregon

Although plague is relatively rare in wild ungulates, this report describes ocular lesions associated with Yersinia pestis infection in three free-ranging mule deer (Odocoileus hemionus) from Wyoming and Oregon, USA. All deer were observed antemortem and seemed to be blind. Post-mortem examination revealed gross lesions of bilateral keratoconjunctivitis and/or panophthalmitis in the first two deer, but only partial retinal detachment in the third deer. Microscopically, all deer had moderate-to-severe necrotizing and fibrinopurulent endophthalmitis and varying degrees of keratoconjunctivitis with abundant intralesional coccobacilli. The lesions in the first (D1) and third deer (D3) suggested an acute course, whereas those in the second deer (D2) were subacute to chronic. Yersinia pestis was isolated from ocular tissue swabs or ocular fluids of D1 and D2, and it was demonstrated by immunohistochemistry within ocular lesions of D1 and D3. Although plague does not seem to be a major cause of morbidity or mortality in free-ranging mule deer, keratoconjunctivitis or pinkeye is relatively common in these animals and plague should be considered as a differential diagnosis in such cases, with appropriate precautions taken to protect the human and animal health.

Development of a Management Program for a Mixed Species Wildlife Park Following an Occurrence of Malignant Catarrhal Fever

During late 2001 and early 2002, a mixed species wildlife park in North Carolina experienced an acute outbreak of morbidity and mortality in Pere David's deer (Elaphurus davidianus), axis deer (Axis axis), blackbuck antelope (Antelope cervicapra), white-tailed deer (Odocoileus virginianus), and Rocky Mountain elk (Cervus elaphus). Clinical signs varied from fulminant disease, progressing from depression to bloody scours to death in fewer than 4 days in Pere David's deer, to a more protracted form of disease, ranging from 2 wk to 3 mo, in axis deer. In moribund axis deer, high levels of anti-malignant catarrhal fever (MCF) virus antibody by competitive-inhibition enzyme-linked immunosorbent assay were detected. Ovine herpesvirus 2 (OvHV-2) DNA was detected in peripheral blood leukocytes of the affected axis deer. No other MCF viruses were detected. Retrospective examination of frozen tissue samples from the affected Pere David's deer and blackbuck antelope also confirmed the presence of OvHV-2 DNA. Initial control efforts were directed at preventing further deaths of clinically susceptible animals by removing MCF virus reservoir species, particularly ovine species. The most prevalent ovine species in the wildlife park was mouflon sheep (Ovis musimon). All sheep were removed from the park by June 2002, and the last MCF death occurred in October 2002. Since mouflon sheep had been a prominent attraction in the wildlife park, the owner wanted a means to reintroduce this species to the park. Derivation of OvHV-2-uninfected mouflon lambs was undertaken using the previously described program for production of OvHV-2-free sheep (Ovis ovis). The rederived MCF virus-negative mouflon sheep were introduced into the park in approximately January 2004. As of December 2007, no further cases of MCF have occurred since the removal of OvHV-2-positive mouflon sheep and reintroduction of the virus-free lambs. This paper describes the successful management and control of MCF in a densely populated mixed species animal park.

Florida Key deer Odocoileus virginianus clavium underpass use and movements along a highway corridor

Abstract In order to address endangered Florida Key deer Odocoileus virginianus clavium vehicle collisions along a 5.6-km segment of United States Highway 1 (US 1), the Florida Department of Transportation (FDOT) constructed a 2.6-km long system of fencing, deer guards and two underpasses to exclude deer from roadway. The US 1 project was completed in 2002 for the purpose of minimizing Key deer mortality and maintaining deer permeability through the Big Pine Key (BPK) corridor, Florida, USA. We evaluated the potential impact of these modifications to Key deer movements by comparing 1) annual ranges and movements of Key deer pre- (January 1998 - December 2000) and post-construction (February 2003 - January 2004), 2) deer-vehicle collisions on US 1 pre- and post-construction, and 3) underpass use post-construction. Mean female and male annual ranges and core areas did not change (P>0.05) between pre- and post-construction. Deer movements within the US 1 project area were comparable pre- (six of 23 radio-col...

Effects of US 1 Project on Florida Key Deer Mortality

ABSTRACT Approximately 26% of annual mortality for the endangered Florida Key deer (Odocoileus virginianus clavium) occurs as deer‐vehicle collisions (DVCs) on the 5.6‐km section of United States Highway 1 (US 1) on Big Pine Key (BPK), but extensive urban development adjacent to sections of US 1 complicates efforts to reduce DVCs. Our objective was to evaluate the effectiveness of the US 1 Project (continuous 2.6‐km system of 2.4‐m fencing, 2 underpasses, and 4 experimental deer guards constructed on US 1 on BPK) in reducing DVCs along US 1. Deer used the underpasses all 3 postproject years (2003–2005); however, we observed higher underpass use in 2004 and 2005 compared to 2003. Exclusion fencing reduced deer intrusions onto the fenced section of US 1 during the 3‐year period (2003, n = 7 deer; 2004, n = 4; 2005, n = 12). With a reduction of deer intrusions onto this section of US 1, DVCs decreased in the fenced area by 73–100%; however, US 1 DVCs within the unfenced sections of US 1 also increased (40%) as expected. In controlling for effects of increasing deer density and traffic volume, study results suggest that highway improvements have decreased the net risk of DVCs along US 1, which indicates that use of deer fencing, deer guards, and underpasses is applicable in other urban communities experiencing unacceptable levels of DVCs.

Observations on Capturing and Aging Deer Fawns

Abstract During a study of fawn mortality of sympatric white-tailed (Odocoileus virginianus) and mule deer (O. hemionus eremicus) in west-central Texas from 2004 to 2006, we made observations that should help deer researchers increase their efficiency of capture of fawns, obtain better estimates of ages of fawns, and obtain more reliable estimates of fawn survival. We experimented with vaginal-implant transmitter designs and found that larger holding wings and antennas protruding <1 cm past the vulva resulted in more successful drops at birth sites. White-tailed fawns moved farther from birth sites than mule deer fawns of similar ages (P = 0.027). Our model predicted that white-tailed and mule deer fawns moved an average of 100 m away from birth sites after 12.5 and 17.5 h postpartum, respectively; outliers may be expected. Compared to previously published models estimating ages of captive fawns from new hoof growth, our model predicted that free-ranging fawns were generally 1.5 weeks older. As others hav...

The role of the wolf in shaping a multi‐species ungulate community in the Italian western Alps

The impact of predation by wolves on prey populations was analysed in a portion of the western Alps characterized by a rich wild ungulate community. The number of wolves ranged from 7 to 15 (1.7–2.9 wolves/100 km2) during the study period (2000–2001). The diet of wolves mainly consisted of wild ungulates. Red deer and roe deer were the staple prey, while chamois was consumed less despite its high density. From 2000 to 2002, wolves annually removed 20–34 red deer, 21–58 roe deer, and 7–14 chamois per 100 km2. These amounts were equivalent to 19–51% of the annual mortality of red deer, 6–28% of roe deer and 6–9% of chamois. Additionally, hunting accounted for 58–94% of the annual mortality of red deer, 18–29% of roe deer and 22–43% of chamois. Other mortality factors (i.e. traffic accidents, disease, poaching) constituted a small percentage of the annual mortality of red deer (5–6%), roe deer (6–9%) and chamois (1%). During the study period, the density of prey animals was stable. Wolf predation did not seriously affect ungulate populations. The role of wolves on wild ungulate populations in the Susa Valley seemed to be compensatory.

Modern hunting behavior in the early Middle Paleolithic: Faunal remains from Misliya Cave, Mount Carmel, Israel

Understanding the behavioral adaptations and subsistence strategies of Middle Paleolithic humans is critical in the debate over the evolution and manifestations of modern human behavior. The study of faunal remains plays a central role in this context. Until now, the majority of Levantine archaeofaunal evidence was derived from late Middle Paleolithic sites. The discovery of faunal remains from Misliya Cave, Mount Carmel, Israel (>200 ka), allowed for detailed taphonomic and zooarchaeological analyses of these early Middle Paleolithic remains. The Misliya Cave faunal assemblage is overwhelmingly dominated by ungulate taxa. The most common prey species is the Mesopotamian fallow deer ( Dama mesopotamica), followed closely by the mountain gazelle ( Gazella gazella). Some aurochs ( Bos primigenius) remains are also present. Small-game species are rare. The fallow deer mortality pattern is dominated by prime-aged individuals. A multivariate taphonomic analysis demonstrates (1) that the assemblage was created solely by humans occupying the cave and was primarily modified by their food-processing activities; and (2) that gazelle carcasses were transported complete to the site, while fallow deer carcasses underwent some field butchery. The new zooarchaeological data from Misliya Cave, particularly the abundance of meat-bearing limb bones displaying filleting cut marks and the acquisition of prime-age prey, demonstrate that early Middle Paleolithic people possessed developed hunting capabilities. Thus, modern large-game hunting, carcass transport, and meat-processing behaviors were already established in the Levant in the early Middle Paleolithic, more than 200 ka ago.

Effects of Winter‐Feeding on Mule Deer in Northern Utah

Abstract: During severe winters, mule deer (Odocoileus hemionus) concentrated on ranges in poor condition can experience high mortality. Winter‐feeding programs have been implemented to mitigate this mortality. We studied effects on body condition, mortality, fawn production, and migration of mule deer following winter‐feeding in the Cache‐Wasatch Mountains of northern Utah, USA. Fed deer exhibited 12% higher live body‐condition indices both years (main effect feed: F1,7.32 = 5.39, P = 0.052), lower mortality (33% vs. 55%: χ21= 4.58, P &lt; 0.05), and produced more fawns (19 fawns:18 fed F vs. 11 fawns:12 nonfed F; t27.2 = 2.20, P &lt; 0.036) than nonfed deer. Fed deer migrated later in spring 2004 (x̄ = 13 Apr) than nonfed deer (x̄ = 24 Mar; t34= 3.25, P = 0.003). Fed deer spent more time on winter range in 2003‐2004 (x̄ = 157 d) than nonfed deer (x̄ = 121 d; t20 = 3.63, P = 0.002), and more time on winter range for both winters combined (fed deer x̄ = 321 d, nonfed deer x̄ = 257 d; t27 = 3.29, P = 0.003). Concomitantly, wildlife managers need to recognize that any possible benefits accrued to mule deer populations in terms of increased nutritional status as a result of winter‐feeding programs may be mitigated by altered timing of migration and increased duration of use of seasonal ranges by fed deer.

Condition, Survival, and Cause‐Specific Mortality of Adult Female Mule Deer in North‐Central New Mexico

Abstract: From December 2001 to December 2004 we monitored 30–44 adult female mule deer (Odocoileus hemionus) annually to assess the factors affecting survival and cause‐specific mortality. We found adult female survival of 0.63 (SE = 0.08), 0.90 (SE = 0.05), and 0.91 (SE = 0.04), 2002–2004, respectively. Starvation was the most common cause of mortality, accounting for 11/23 mortalities. Mean ingesta‐free body fat (IFBF) levels of adult females in December were low (6–9%), despite few (0–13%) lactating adult females, indicative of extremely nutritionally deficient summer—autumn ranges throughout the study site. A priori levels of IFBF and rump body condition scores (rBCS) were higher in deer that survived the following year regardless of cause of mortality. Logistical analysis indicated that models containing individual body fat, rBCS, mean population body fat, winter precipitation, precipitation during mid‐ to late gestation, and total annual precipitation were related (x2 ≥ 9.1; P ≤ 0.003) to deer survival, with individual IFBF (β =‐0.47 [SE = 0.21]; odds ratio = 0.63 [0.42‐0.94]) and population mean IFBF (β = ‐1.94 [SE = 0.68]; odds ratio = 0.14 [0.04‐0.54]) the best predictors; with either variable, probability of dying decreased as fat levels increased. Fawn production was low (2–29 fawns/100 ad F) and, combined with adult survival, resulted in estimated population rates of increase of ‐35%, ‐5%, and +6% for 2002–2004, respectively. Deer survival and population performance were limited in north‐central New Mexico, USA, due to poor condition of deer, likely a result of limited food resulting from both drought and long‐term changes in plant communities. Precipitation during mid‐ to late gestation was also important for adult female survival in north‐central New Mexico.

Failure to Detect Bovine Viral Diarrhea Virus in Necropsied Farm-Raised White-Tailed Deer (Odocoileus Virginianus) in Pennsylvania

Between January 1 and December 31, 2005 gross and histologic examinations were performed on carcasses of 61 farm-raised white-tailed deer originating from Pennsylvania. Single-tube real-time reverse transcription polymerase chain reaction (real-time RT-PCR) for the detection of bovine viral diarrhea virus type 1 (BVDV-1) and type 2 (BVDV-2) was performed on each animal. Virus isolation was performed on tissue samples from 25 of 61 animals. Immunohistochemical (IHC) staining of ear-notch skin to identify BVDV antigen was performed on each animal. All tissues samples tested negative for both BVDV-1 and BVDV-2 by real-time RT-PCR, virus isolation, and IHC. Gross or histopathologic lesions suggestive of BVDV infection were not detected. Results of this study suggest that BVD is not a common cause of mortality in farm-raised white-tailed deer in Pennsylvania.

Survival and Cause‐Specific Mortality of Male Mule Deer Under Different Hunting Regulations in the Bridger Mountains, Montana

Abstract: We selected 2 adjacent populations of mule deer (Odocoileus hemionus hemionus) in the Bridger Mountains, Montana, USA, to measure effects on survival rates and causes of mortality of 2 hunting regulations designed to enhance representation of mature males. We compared male survival between the West Slope and South 16 Mile populations considering both hunting and nonhunting sources of mortality with respect to age (fawn, yearling, and mature), month (Jun‐May), and year (1990‐1995). Harvest rates of mature males were greater than for yearlings, demonstrating hunter preferences. We found no differences in yearling monthly survival rates between October and November or between areas or years. In contrast, we found survival of mature males differed between October and November and across years and study areas. During these months, survival rates of mature males averaged 0.602 on the West Slope under the 2‐point regulation and 0.762 on South 16 Mile under the outfitted hunt. Monthly survival during summer also differed by age class, but not area, with estimates of 0.963 for yearling males, and corresponding mature male survival estimates of 0.991, demonstrating greater yearling summer mortality. Winter survival rates of yearlings and matures were similar for both areas with a monthly estimate of 0.986. We found differences in spring monthly survival estimates for the 2 areas, mainly for matures. Yearling male monthly survival estimates were 0.959 and 0.958 for the 2 areas, whereas corresponding mature male estimates during spring were 0.991 and 0.936 on the West Slope and South 16 Mile, respectively. Fawn survival rates varied from 0.101 to 0.770 among years and between areas overwinter. Cumulative effects of nonhunting mortality among all age classes reduced the effectiveness of 2 hunting regulations designed to enhance survival of males to age classes ≥4 years associated with maximum antler development despite accomplishing reductions in harvest rates. Low and variable fawn survival and relatively high nonhunting‐related losses of yearling and mature males might be typical of many populations in the Northern Rocky Mountains. Deer managers should avoid populations coexisting with a diversity of large predators in environments with strong year effects when considering opportunities for implementing harvest regulations to improve representation of mature males.

Survival and Cause‐Specific Mortality of Mature Male White‐Tailed Deer

ABSTRACT Understanding sources of male deer mortality is a prerequisite to a successful management program, especially in Texas, USA, where white‐tailed deer (Odocoileus virginianus) are the most economically important game species. South Texas, USA, is one of the few areas where males reach older age classes (&gt; 4.5 yr), in part because of intense population management. Therefore, we obtained survival rates and causes of mortality of 48 mature male deer in south Texas, USA, over 2 years. We calculated Kaplan—Meier survival estimates during 2 study years modified for a staggered‐entry design and annual survival rates for one cohort of deer from 1998 to 2004 using recapture and radiotelemetry data. We documented 21 mortalities (16 harvest and 5 nonhunting mortalities). Average annual survival of the known‐aged 1998 cohort was 82% with 52% of surviving to 6.5 years of age. Survival in study year 2 (0.497 ± 0.069) was less than in study year 1 (0.781 ± 0.073; P = 0.0047), largely because males had finally reached harvestable age (&gt; 6.5 yr old). All but one non‐harvest mortality occurred during the rut or postrut periods. It appears that a large percentage of males can reach mature age classes under intense population management, making them available for harvest when at peak antler size. This allows for increased economic returns on intensively managed white‐tailed deer populations.

Risk Factors and Mortality of Black-Tailed Deer in a Managed Forest Landscape

We investigated the influence of habitat use on the risk of death of Sitka black-tailed deer (Odocoileus hemionus sitkensis) on Heceta Island in Southeast Alaska, USA. A mosaic of even and uneven-aged forests covered much of the island and provided a model setting in which to assess relationships between habitat use and mortality of deer. We radiocollared and monitored 51 adult females, 11 adult males, and 19 young of the year. We compared risk of death with habitat composition, habitat distribution, topography, distances to features such as roads, and functional habitat characteristics such as seasonal forage biomass within 50-, 500-, and 1,000-m circular buffers around relocations of deer. Those buffers encompassed habitats used at scales of radio-locations, home ranges, and landscapes. We addressed hypotheses that related habitat composition and distribution to risk of death from malnutrition, predation, and hunting. Predation by wolves (Canis lupus) and malnutrition were the principal causes of death of adult females and young, whereas hunters killed most adult males. Habitat factors at scales of 500 and 1,000 m had the greatest effect on mortality of adult females and young, whereas habitat characteristics in the immediate vicinity of radio relocations had the greatest effect on mortality of adult males. Malnutrition was positively associated with use of forage-poor habitats such as pole-stage, second-growth forest. Use of precommercially thinned second growth increased risk of death for young deer. Use of level terrain was the most influential factor with respect to predation and increased risk of death at all scales. Use of open habitats, such as muskegs and young clearcuts, also increased risk of death. Use of shrub-sapling-stage clearcuts in landscapes accessible by roads increased risk of death from hunting. We showed that use of specific habitats and the landscape context of those habitats were important factors influencing mortality of deer. We also demonstrated the importance of comparing habitat use with measures of fitness rather than simply with availability when evaluating habitat suitability for deer. Our results should be useful to wildlife researchers investigating contributions of habitat to fitness and population dynamics of ungulates, and to wildlife managers attempting to manipulate habitats to benefit deer populations.

Impact of puma predation on the decline and recovery of a mule deer population in southeastern Idaho

We modeled the impact of puma ( Puma concolor (L., 1771)) predation on the decline and recovery of mule deer ( Odocoileus hemionus (Rafinesque, 1817)) in southern Idaho based on estimates of puma numbers, predation rates of pumas, and reproductive variables of deer. Deer populations peaked in 1992–1993, then declined more than 55% and remained low for the next 11 years. Puma numbers peaked 4–6 years after deer populations peaked but then declined to original levels. Estimated puma predation on the deer population before and after the decline was 2.2%–3.3% and 3.1%–5.8%, respectively. At high puma densities (&gt;3 pumas/100 km2), predation by pumas delayed deer recovery by 2–3 years. Percent winter mortality of fawns (r2 = 0.62, P &lt; 0.001) and adult female deer (r2 = 0.68, P &lt; 0.001) correlated positively with December–January snowfall. Incorporation of winter snowfall amounts in the model produced a pattern of deer population change matching estimated changes based on field survey data. We conclude that pumas probably were a minor factor in the decline of the deer population in our area and did not suppress deer recovery. We propose that winter snowfall was the primary ultimate and proximate factor in the deer decline and suppression of their recovery.

SURGICAL TECHNIQUE FOR TUBAL LIGATION IN WHITE‐TAILED DEER (ODOCOILEUS VIRGINIANUS)

Surgical tubal ligation was used to sterilize urban free-ranging white-tailed deer (Odocoileus virginianus) as a methodology of a larger study investigating the influences of intact, sterile females on population dynamics and behavior. Deer were either trapped in clover traps (n = 55) and induced with an i.m. injection of xylazine and tiletamine/zolazepam or induced by a similar protocol by dart (n = 12), then intubated and maintained on isoflurane in oxygen. Over 3 yr, individual female deer (n = 103) were captured in Highland Park, Illinois, with a subset of females sterilized using tubal ligation by ventral laparotomy (n = 63). Other sterilization procedures included tubal transection by ventral (n = 1) or right lateral (n = 2) laparoscopy and ovariohysterectomy by ventral laparotomy (n = 1). One mortality (1/ 67, 1.5%) of a doe with an advanced pregnancy was attributed to a lengthy right lateral laparoscopic surgery that was converted to a right lateral laparotomy. The initial surgical modality of laparoscopy was altered in favor of a ventral laparotomy for simplification of the project and improved surgical access in late-term gravid does. Laparotomy techniques included oviductal ligation and transection (n = 14), application of an oviductal mechanical clip (n = 9), ligation and partial salpingectomy (n = 40), and ovariohysterectomy (n = 1). As of 2 yr poststerilization, no surgical does were observed with fawns, indicating that these procedures provide sterilization with low mortality in urban white-tailed deer.

Regulating Hunter Baiting for White-Tailed Deer in Michigan: Biological and Social Considerations

Eradication of bovine tuberculosis (TB) from free-ranging white-tailed deer (Odocoileus virginianus) requires mortality rates of infected deer exceed the rate of new infection. Efforts to reduce TB transmission in Michigan, USA, are based on 2 assumptions: 1) deer mortality may be increased through recreational hunting, and 2) encounter rates between infected and noninfected deer may be reduced by prohibiting baiting and supplemental feeding. Spatial correlation of TB-infected deer and supplemental feeding sites detected using aerial surveys validated a ban on artificial feeding in Michigan. Similar analysis could not be used to evaluate the effects of a baiting ban because bait distribution was unknown. Furthermore, a ban on deer baiting could confound attempts to increase deer mortality through reduced hunter participation or efficacy. We reviewed the process used to evaluate a strategy for regulating bait use by hunters. This review included an assessment of 5 factors: statewide spatial analysis of apparent TB prevalence, deer intraspecific interactions at bait sites, effects of bait on hunter harvest rates, impacts of disease presence and practice of eradication efforts on hunting participation in the infected area, and input from law enforcement personnel. Our analysis suggested that restricting baiting to a limited, consistent region incurred less biological risk than allowing bait to be used statewide and less political risk than a statewide ban.

Effects of Environmental Salinity on Vertebrate Florivory and Wetland Communities

Iris hexagona is a perennial freshwater species indigenous to Louisiana wetlands. Coastal iris populations that are exposed to saline conditions often suffer heavy floral browsing. This paper is the first to photographically document florivory by white-tailed deer (Odocoileus virginianus Zimmerman), which consume iris flowers and immature seed capsules. Severe florivory can prevent sexual reproduction in plants and eliminate habitat for floral arthropods. In this three-year study, we monitored environmental salinity, assessed natural levels of florivory, and established deer exclosures to test the effects of florivory on arthropod abundance and diversity. In two out of three years, florivory rates were positively correlated with the level of salinity at individual I. hexagona populations. In all three years, florivory in the brackish marsh was an order of magnitude greater than florivory in intermediate and freshwater sites. In 2003, the number and diversity of arthropods was significantly greater on unbrowsed (caged) than browsed (open) irises. In October 2002, Hurricane Lili struck our main study site, causing extensive damage to the landscape and heavy deer mortality. Despite this, floral browsing was high (88%) in spring 2003, and arthropod numbers and diversity declined significantly. Our results suggest that salinity may facilitate floral browsing, which can have direct effects on plant fitness and indirect consequences for arthropod communities in wetland plant populations.

MULE DEER SURVIVAL AMONG ADJACENT POPULATIONS IN SOUTHWEST IDAHO

Abstract We investigated survival and cause-specific mortality of mule deer (Odocoileus hemionus) on 3 distinct winter ranges in southwest Idaho from 1992 to 1997 to identify demographic variation and potential limiting factors based on a sample of 447 radiocollared deer. During winters 1995–1996 and 1996–1997, we modeled overwinter fawn mortality based on early winter mass, sex, activity, and habitat use variables. Annual survival rates of adult mule deer varied among the 3 adjacent study areas (χ22 = 10.93, P = 0.004). Overwinter deer survival also varied among study areas (χ22 = 8.00, P = 0.018), and the study area × year, study area × sex, and study area × age interactions were all significant (P ≤ 0.018). Overwinter survival differences among the study areas were not consistent over time or among sexes and ages of deer. Winter malnutrition was the main cause of mortality for both adults and fawns during the severe winter of 1992–1993, when overall survival was low. Excluding harvest, predation was th...