Survival, Birth Characteristics, and Cause-Specific Mortality of White-Tailed Deer Neonates

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-alpha (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. (JOURNAL OF WILDLIFE MANAGEMENT 73(2): 175-183; 2009)