PARENT SESSION
Thursday, August 10, 8:00-11:30 am
COS 85 - Predator-prey interactions
L-11, Lobby Level, Cook Convention Center
Presiders: J Laundre

Tadpole prey and odonate predator spatial distributions and the effects of light and intraguild predation.

Luttbeg, Barney^*,1, Hammond, John¹, Sih, Andrew¹, ¹ University of California, Davis, Davis, CA

ABSTRACT- Very little is known about how predators and prey interactively shape each other's spatial distributions. A general prediction is that the distribution of the prey's resources will have less of an effect on the prey and predator spatial distributions as the threat of predation risk increases, either from higher predator densities or higher per capita predation rates. We tested this prediction by observing the spatial distributions of Pacific tree frog tadpoles (Pseudacris regilla) and Anax nymphs predators in two patch experimental arenas with different densities of the prey's resources and with full and dimmed light. Prey distributions were unaffected by the presence of predators or the light treatment and in all cases tended towards matching the distribution of their resources. Predator distributions were affected by the presence of prey and the light treatment. In the absence of prey, predators tended to match the prey's resources in dimmed light, but not in full light. In the presence of prey, predators tended to be uniformly distributed. These results differ from previous results with different predators, in which prey spatial distributions were significantly altered by the presence of predators. Analyses of patch movements suggest that in this experiment predators were primarily moving to avoid other predators and prey were moving to the patch with more resources. Unlike previous experiments, intraguild predation was observed, and we present a model to suggest that this could cause the observed changes in how predators and prey were distributed.

Key words: predator-prey interactions, behavioral ecology, amphibian