Understanding survival of and factors that may predispose newborn deer (Odocoileus spp.) to mortality contribute to improved understanding of population dynamics. We captured free‐ranging white‐tailed deer neonates (n = 66) of radiocollared females that survived severe (Winter Severity Index [WSI] = 153) and mild (WSI = 45) winters 2000–2001 and 2001–2002. Mean dates of birth (26 May ± 1.7 [SE] days and 26 May ± 1.3 days) and estimated birth‐masses of 2.8 ± 0.1 kg and 3.0 ± 0.1 kg were similar between springs 2001 (n = 31) and 2002 (n = 35), respectively. Neonate survival was similar between years; pooled mortality rates of neonates were 0.14, 0.11, and 0.20 at 0–1 weeks, 2–4 weeks, and 5–12 weeks of age, respectively, and overall survival rate for neonates to 12 weeks of age was 0.47. Predation accounted for 86% of mortality; the remaining 14% of deaths were attributed to unknown causes. Black bears (Ursus americanus) were responsible for 57% and 38% of predation of neonates in springs 2001 and 2002, respectively, whereas bobcats (Felis rufus) accounted for 50% in 2002. Wolves (Canis lupus) accounted for only 5% of predator‐related deaths. Low birth‐mass, smaller body size, and elevated concentrations of serum urea nitrogen (26.1 ± 2.6 mg/dL vs 19.3 ± 0.8 mg/dL) and tumor necrosis factor‐α (82.6 ± 78.6 pg/mL vs. 2.3 ± 0.5 pg/mL) were associated with neonates that died within 1 week of birth. Even though we did not detect a direct relation between winter severity and birth or blood characteristics of neonates, evidence suggests that birth‐mass and key serum indices of neonate nutrition were associated with their early mortality. Thus, managers can make more informed predictions regarding survival and cause‐specific mortality of fawns and adjust management strategies to better control deer population goals.

Improved understanding of the margins of safe capture, chemical immobilization, and handling of free‐ranging animals for research and management relies on the documentation and examination of efforts involving various species, study designs, and environmental conditions. During 1991–2002 we had 984 captures and recaptures of white‐tailed deer (Odocoileus virginianus), primarily by Clover trap, under a wide range of winter weather conditions and in an area saturated with wolves (Canis lupus). We captured and recaptured 337 radiocollared females (0.5–15.5 years old) 652 times. Total capture‐related mortality was 5.4% (35 of 652). The incidence of capture accidents (e.g., trauma‐induced paralysis, death) was 2.9%, and mortality that occurred within 14 days of release was 2.5%. Mean time to mortality for this latter group was 6 days (SE = 1.1 days, n = 16); wolf predation within 11 days was the proximate cause of 50% of these mortalities. A priori, we selected immobilization time for analysis by logistic regression to test for a potential effect of capture and handling on mortality while controlling for known risk factors (age, winter severity) but found no significant effects. Additionally, subsequent comparisons of means and standard errors (SEs) showed no differences among numerous aspects of the capture, immobilization, handling, or associated weather conditions. Success in capture and handling of free‐ranging deer results in smaller sample sizes of capture‐related deaths (i.e., events), which makes it difficult to infer causal relations between environmental variables, handling procedures, and capture‐related mortality. The strength of such studies is that they may serve to demonstrate a range of conditions (environmental variables and handling procedures) over which capture‐related mortality can be controlled at acceptably low levels.

No abstract

BackgoundLong-term studies allow capture of a wide breadth of environmental variability and a broader context within which to maximize our understanding of relationships to specific aspects of wildlife behavior. The goal of our study was to improve our understanding of the biological value of dense conifer cover to deer on winter range relative to snow depth and ambient temperature.Methodology/Principal FindingsWe examined variation among deer in their use of dense conifer cover during a 12-year study period as potentially influenced by winter severity and cover availability. Female deer were fitted with a mixture of very high frequency (VHF, n = 267) and Global Positioning System (GPS, n = 24) collars for monitoring use of specific cover types at the population and individual levels, respectively. We developed habitat composites for four study sites. We fit multinomial response models to VHF (daytime) data to describe population-level use patterns as a function of snow depth, ambient temperature, and cover availability. To develop alternative hypotheses regarding expected spatio-temporal patterns in the use of dense conifer cover, we considered two sets of competing sub-hypotheses. The first set addressed whether or not dense conifer cover was limiting on the four study sites. The second set considered four alternative sub-hypotheses regarding the potential influence of snow depth and ambient temperature on space use patterns. Deer use of dense conifer cover increased the most with increasing snow depth and most abruptly on the two sites where it was most available, suggestive of an energy conservation strategy. Deer use of dense cover decreased the most with decreasing temperatures on the sites where it was most available. At all four sites deer made greater daytime use (55 to >80% probability of use) of open vegetation types at the lowest daily minimum temperatures indicating the importance of thermal benefits afforded from increased exposure to solar radiation. Date-time plots of GPS data (24 hr) allowed us to explore individual diurnal and seasonal patterns of habitat use relative to changes in snow depth. There was significant among-animal variability in their propensity to be found in three density classes of conifer cover and other open types, but little difference between diurnal and nocturnal patterns of habitat use.Conclusions/SignificanceConsistent with our findings reported elsewhere that snow depth has a greater impact on deer survival than ambient temperature, herein our population-level results highlight the importance of dense conifer cover as snow shelter rather than thermal cover. Collectively, our findings suggest that maximizing availability of dense conifer cover in an energetically beneficial arrangement with quality feeding sites should be a prominent component of habitat management for deer.