COS 119-4 - CANCELLED - Navigating a manipulated risk landscape: predation risk changes ungulate movement, space use, and resource selection

Background/Question/Methods

Predation risk is a fundamental factor influencing the spatial ecology of prey species as the consequences of movement and space use decisions can directly affect lifetime reproductive output, or individual fitness. Numerous field studies describe the effects of predation risk on the spatial ecology of ungulates; however, the mobility of these animals lends to logistical constraints on experimental methods evaluating the effects of spatially variable risk on their movement and space use. Consequently, experimental investigations of spatial risk responses in ungulates generally rely on simulations of predator presence to induce risk responses associated with perceived predation risk rather than actual risk of predation. Accordingly, we manipulated true risk of predation to test important ecological hypotheses related to spatial behaviors of prey. Using GPS-telemetry data collected on 18 female white-tailed deer (Odocoileus virginianus) during fawn-rearing (JUL-SEP), we evaluated the effects of predation risk on prey spatial behaviors including home range size, movement rates, and resource selection.

Results/Conclusions

By isolating risk as a treatment with prey-permeable predator exclusion fencing, we provide the first experimental test of the ‘risky places’ hypothesis in a free-ranging ungulate population. We observed significantly shorter step lengths, smaller home range areas, and altered selection of pine and hardwood forests in risk-free areas relative to risk-exposed areas. Our results provide the first experimental linkage between ungulate spatial ecology and spatial variation in true predation risk and demonstrate that predation risk induces substantial shifts in female deer behavior during fawn-rearing, a critical period determining female fitness. Furthermore, observed differences in space use and resource selection across spatially variable risk indicate that, while bottom-up factors propagate variability in structure and forage quality across habitat types, top-down forces alter habitat quality within habitat types.