White-tailed deer neonate survival in the absence of predators

Several factors influence neonate survival rates in white-tailed deer (Odocoileus virginianus), and an emphasis on predation as the primary limiting factor to neonate recruitment may serve to detract researchers from understanding other influential variables. We estimated survival and cause-specific mortality of white-tailed deer neonates in the absence of predators with an emphasis on assessing how birth mass, dam maturity, and weather covariates affect neonate survival. Additionally, we examined the influence of capture method (opportunistic searches vs. vaginal implant transmitter; VIT) on survival estimates. We captured 109 neonates using opportunistic capture (n = 55) and VITs (n = 54) in Sussex County, Delaware, USA, during 2016 and 2017. There are no established predator populations (i.e., black bear, bobcat, and coyote) within the study area. We observed greater 90-d survival rates in opportunistically captured neonates (0.69, 95% CI = 0.55-0.87) compared to VIT-captured neonates (0.44, 95% CI = 0.34-0.61), a difference driven by inobservance of early-life mortality events among neonates captured opportunistically. Natural causes excluding predation (e.g., disease, emaciation, and birth defects) accounted for all observed mortality (n = 42). Mortality related to disease, emaciation, and birth defects typically occurred in the first 7 d of life and was underrepresented in the opportunistically captured sample. Birth mass, dam age class, and precipitation influenced neonate mortality risk within the first 7 d of life, but no variables were associated with survival from 8 to 28 d of life. Non-predation-related mortality causes in our study area resulted in survival rates comparable to regions with established predator communities. Non-predation-related mortality may be the ultimate driving factor controlling neonatal survival in other regions but can be obfuscated by more proximal mortality sources, such as predation.