Funded Research Projects: WS

Does Anti-predator Behavior Modify Indirect Effects of Top Predators?

Research Sponsored By: National Science Foundation (NSF)
Principal Investigator: Aaron Wirsing
Project Description
Project goal is to test whether recolonizing gray wolves (Canis lupus) in the Methow Valley of north-central Washington state exert contrasting indirect effects on plants by inducing divergent winter habitat shifts by two sympatric herbivores -- mule deer (Odocoileus hemionus) and white-tailed deer (Odocoileus virginianus)-- with different escape tactics. A recent review reveals that spatial responses to predators can vary with prey escape mode. By implication, predators could exert multiple and spatially opposing indirect effects on species serving as food for prey that are mediated by divergent spatial shifts of sympatric prey species with different means of escape. No study to date has explored this intriguing possibility. Mule deer escape predators by stotting, a tactic that ostensibly provides an advantage against coursing predators over rugged terrain. In contrast, white-tailed deer escape predators with sprints that are most effective on gentle terrain with few obstacles. Thus, we predict that mule deer exposed to wolves will shift to, and forage more heavily in, shrub-steppe habitats where the terrain is broken, whereas white-tailed deer should shift to riparian habitats where the terrain is gentle. As a result, we expect that wolves will indirectly shelter plants growing in shrub-steppe habitats from white-tailed deer herbivory while exposing them to increased pressure from mule deer, and that these top predators will exert the opposite indirect effect in riparian habitats.