Neonatal survival and spatial ecology of adult female white-tailed deer in the functional absence of predators

Abstract

White-tailed deer neonatal survival and adult female spatial behaviors are influenced by a wide array of variables. The emphasis on predator management as the driving factor in neonatal survival has distracted researchers from investigating other influential variables effecting survival, while female spatial behavior remains under-studied in many systems. My overall objectives for this research were to (1) determine neonatal survival, (2) adult female spatial behavior, and (3) birth site selection in the absence of predators. I captured 52 adult females, followed by 109 neonates using opportunistic capture (n = 55) and vaginal implant transmitters (VIT; n = 54) in Sussex County, Delaware, USA during 2016 and 2017. Predators (i.e., black bear, bobcat, and coyotes) were functionally absent from the study area. The overall 90-day survival estimate was 0.54 (95% CI = 0.45 – 0.66). Opportunistically captured neonates had greater survival by 0.24, compared to VIT captured neonates (z = 14.7; P < 0.01). Natural causes (n = 42) accounted for all of my observed mortality. The top supported models included covariates for birth weight, doe maturity, and precipitation in the 7and 30-day windows. Natural mortality is likely the ultimate mechanism controlling neonatal survival but is masked by the emphasis on predation and the inflated survival estimates caused by opportunistic capture. ☐ Females decreased home range size following parturition with the smallest home ranges observed at 2 weeks post-parturition. Females who lost their fawns immediately increased their home range size back to pre-parturition sizes. Doe-to-fawn proximity decreased steadily, reaching its smallest distance at 4 weeks post-parturition. Mature females occupied smaller home ranges and remained closer to their neonates for the first 5-6 weeks following parturition. The observed spatial behaviors fit well with trends in isolation behavior among females and timing of weaning for neonates. ☐ In the absence of predators, females continued to select birth sites with superior predator avoidance cover. Females selected birth sites with 8% more horizontal cover than at paired-random sites. Canopy closure and basal area did not differ between observed and random sites, but this was likely due to the similarity in overstory composition and structure across large portions of the study area.