Predator exclusion as a management option for increasing white-tailed deer recruitment

Lethal control of coyotes (Canis latrans) is a mechanism for increasing white-tailed deer (Odocoileus virginianus) recruitment but can be difficult to implement and maybe ineffective on small parcels of land because of coyote immigration. In 2003, we constructed 4 40-ha mesopredator exclosures with the objective of quantifying the influence of mesopredators, including coyotes, on select wildlife populations and communities. Camera trapping indicated neonate/adult female white-tailed deer ratios were approximately 2 times greater inside predator exclosures than in control plots. Hunter success data provided further evidence of increased recruitment associated with exclosures relative to the remainder of the study site. Because exclosures were located on the boundary of our study area and off-site white-tailed deer harvest records were not available, we used estimates of deer density, sex ratios, reproductive rates, relative use of exclosures, and neonate survival inside and outside of exclosures to parameterize a Monte Carlo simulation model to estimate the impact of our 4 exclosures on neonate recruitment into the start of the firearms hunting season on a 1,600-ha area. After 1,000 iterations, we estimated that predator exclusion provided an additional 18 ± 0.13 (x̄ ± SE; median = 15, interquartile range [IQR] =9–24) recruits/year above that expected without exclusion. Simulated neonate/adult female ratio was 0.74 ± 0.03 (median = 0.72, IQR = 0.52–0.93) with exclosures and 0.41 ± 0.008 (median = 0.39, IQR = 0.21-0.58) without. Simulated exclosure impact on recruitment was most sensitive to white-tailed deer relative use of exclosures and was least sensitive to neonate survival inside exclosures. We suggest that predator exclusion may be an effective mechanism for reducing neonate mortality and increasing white-tailed deer recruitment in areas where neonate survival is affected by predation. Exclosures maybe particularly valuable on small parcels of land where predator removal would be offset by immigration. Finally, exclosures provide refuge from predators throughout the year, and we hypothesize exclosures may also contribute to adult survival and reduce impacts of predation risk that may also affect white-tailed deer population dynamics. Additional research incorporating variation in exclosure size and white-tailed deer density is needed to better evaluate predator exclosures for creating neonate refugia and mitigating sub-lethal impacts of predation.