Dragonfly larvae and tadpole frog space use games in varied light conditions

Abstract

Predators and prey often engage in a game where predators attempt to be in areas with higher prey densities and prey attempt to be in areas with lower predator densities. A few models have predicted the resulting distributions of predators and prey, but little empirical data exist to test these predictions and to examine how abiotic and biotic factors shape the distributions. Thus, we observed how Anax dragonfly nymphs and Pacific tree frog tadpoles (Pseudacris regilla) either together or separately distributed themselves in an arena with a high- and a low-prey resource patch. Trials were conducted in high- and low-light conditions to manipulate predation risk and to view the effects of this abiotic factor. Counter to the model predictions, we found that predators were not more abundant in high-resource (HR) patches, and they thus did not force prey toward being uniformly distributed. Using a model selection approach to assess what factors affected predator and prey patch-switching movement, we found that prey more often left patches that had more predators present, but predators surprisingly more often left patches with more prey present. Light levels did not affect predation risk; however, in the dark with the associated reduction in visual information predators preferred HR patches. This caused a lower coincidence of prey and predators in patches. Predators also switched patches less often when they occupied the same patch as the other predator. This suggests that predator distributions, and indirectly prey distributions, are affected by the risk of intraguild predation. Key words: movement rules, predator and prey spatial distributions, spatial games. [Behav Ecol]