Responses of a large herbivore to predation risk are modulated by intrinsic and extrinsic factors

Abstract

Prey species can perceive and respond to spatiotemporal variation in predation risk to increase survival. In addition to adjusting spatial and temporal activity patterns to avoid predation, prey employ other antipredator behaviors, such as vigilance and fleeing, and these behaviors can be further modulated by intrinsic, environmental, and anthropogenic factors. However, few studies simultaneously examine multiple potential antipredator behavioral responses of prey or examine prey responses to multiple scales of risk. In the southeastern United States, coyotes (Canis latrans) have become established as the top predator of white-tailed deer (Odocoileus virginianus) populations mainly through fawn predation, and deer adjust behaviors in response to coyotes. Using passive camera trap data from summer 2019 to 2021, we simultaneously tested for evidence that deer adjust spatial activity patterns, diel activity patterns, and vigilance behavior in response to various abiotic and biotic factors including long-term and short-term coyote encounter risk. Overall, our results suggest that deer are unable to eliminate the risk of encountering coyotes by modifying their spatial activity and thus employ other demographic-specific behavioral adaptations to reduce coyote encounter risk. Deer nursery groups were significantly more diurnal than adult males or adult female deer traveling alone, likely in an attempt to reduce predation risk for fawns. Deer nursery groups increased spatial activity but decreased vigilance at sites the day following increased wild pig (Sus scrofa) activity, suggesting invasive competitors have impacts on maternal behaviors in deer. Adult female deer collectively increased vigilance at sites with greater long-term coyote encounter risk, and in support of the “many-eyes” hypothesis, were less vigilant when in larger groups. Spatial activity of adult female deer traveling alone was positively related to short-term coyote encounter risk, potentially indicating coyotes seek areas with increased doe activity to help locate fawn prey. The results of our study show that behavioral responses to predators and competitors are modulated by individual state (demography), grouping behavior, and habitat features. Our study highlights the need to analyze multiple potential antipredator behaviors and multiple scales of risk to gain a more complete understanding of prey responses to risk.