Elucidating Predator-Prey Interactions Using Aquatic Microcosms: Complex Effects of a Crayfish Predator, Vegetation, and Atrazine on Tadpole Survival and Behavior

Habitat structure is known to influence community interactions, but its role in amphibian communities is unclear. Our objective was to examine the effect of vegetative habitat structure, in the presence or absence of a crayfish predator (Orconectes rusticus) and the herbicide atrazine, on Green Frog (Rana clamitans) tadpoles reared in 10-L microcosms in the laboratory Crayfish predators reduced Green Frog survival and affected activity levels and microhabitat use differently depending on the presence or absence of vegetation. In treatments with vegetation, activity levels were greater when the crayfish predator was absent, but in treatments without vegetation activity levels did not differ between predation treatments. Moreover, when a crayfish predator was present, tadpoles in treatments without vegetation spent more time at the water surface than tadpoles in treatments with vegetation. This preference for the water surface may have been a compensatory behavioral change to avoid predation because it was less likely that crayfish would be able to reach the upper portion of the tank in the absence of vegetation. Atrazine exposure did not significantly influence susceptibility of Green Frog tadpoles to crayfish predators or alter the impact of vegetation. We found that vegetative habitat structure can mediate predator prey interactions; however, contrary to previous studies we found that the presence of vegetation may benefit the crayfish predator and result in both lethal and sublethal effects on tadpole prey.