When, where, and how prey pair antipredator behaviors to natural and
anthropogenic mortality risks
Abstract
Behavioral responses of prey to predation risk have ecological impacts
that can be as great as the direct mortality. Theory often suggests that
prey pair responses to risks based on the hunting mode of the predator
(hunting mode hypothesis), but prey may ignore hunting mode to
prioritize responding to the most lethal predators (lethality
hypothesis). To test these hypotheses, we evaluated the behavioral
responses of white-tailed deer (Odocoileus virginianus) to risks from
two natural mesopredators and human sources of mortality. Specifically,
we determined, for each source of risk, whether deer responded with
behavioral state changes or spatial avoidance and whether this behavior
changed with time (diurnally and annually). We collared and tracked 40
female and 29 male deer. To determine the response of deer to risk, we
collected data on the distribution of coyotes (Canis latrans), bobcats
(Lynx rufus), human modification, hunters, and roads. We used hidden
Markov models (HMM) to determine whether each covariate impacted the
probability of transitioning between behavioral states and selection
functions (SSF) to determine whether deer spatially avoided each
covariate.Generally, deer changed behavioral state in response to both
mesopredators but avoided human modification. In response to
mesopredators, deer consistently shifted to slower movement behavioral
states. Spatial responses to human modification varied depending on the
time of day. During daylight hours, deer selected for human
modification, but during the crepuscular and nighttime period, deer
avoided human modification. Space use was most strongly related to more
lethal humans, providing support for the lethality hypothesis. Despite
prioritizing humans, mesopredators impacted behavioral state, suggesting
that mesopredators still have important impacts on prey behavior.
Finally, temporal patterns of avoidance align with other studies that
indicate avoidance of predators is time-dependent, but further highlight
the complex push-pull relationship of human modified areas on wildlife.