COS 74-9 - Life in the fast lane: Predator foraging mode influences the effect of antipredator behavior

Wednesday, August 9, 2017: 10:50 AM
E147-148, Oregon Convention Center
Jason S. Sadowski, Department of Environmental Science and Policy, University of California, Davis, Davis, CA; Bodega Marine Lab, Bodega Bay, CA and Edwin D. Grosholz, Department of Environmental Science and Policy, University of California, Davis, CA

Empirical studies have determined that the presence of predators can have strong effects on prey behavior and species interactions. Theoretical models of predator induced changes in prey phenotype have supported the importance of antipredator behavior on community stability. However theoretical studies tend to focus on the general influence of predator presence/absence without considering the mechanism behind induced changes in prey phenotype. To examine how mechanistic changes in prey behavior could influence community structure, we developed a numerical model that incorporated encounter rates dependent on movement through the environment and created an intuitive tradeoff such that prey can hide from predators at the cost of foraging on resources. Like most Lotka-Volterra models, this model assumes infinite space and random movement of predators and prey through the environment. Our model also assumes that predator movement rates are constant and that predators have a radius of detection such that any prey within that radius are consumed. Antipredator behavior is incorporated by allowing prey velocity to decrease as predator density increases.


Overall we find that the velocity of the predator has a major influence on the importance of antipredator behavior. Predators with large movement velocities (mobile predators) override the importance of antipredator behavior and are able to effectively forage on prey regardless of prey antipredator response. On the other hand, predators with small movement velocities (sit and wait predators) are greatly influenced by the magnitude of antipredator behavior. When antipredator behavioral sensitivity was set to reduce prey velocity by 90% at equilibrium, prey densities reached their maximum values when both predator and prey velocities were small and their minimum values at high predator velocities. These theoretical results agree well with the empirically demonstrated importance of cues from sit-and-wait predators. Furthermore we found that antipredator behavior is more likely to create stable communities with sit-and-wait predators than with mobile predators. We posit that sit-and-wait predator cues are not only more reliable, but that responding to these cues is more advantageous to prey density and community stability. We will also discuss potential implications of the importance of antipredator behavior on invasive species dynamics.