Can Prey Use Dietary Cues To Distinguish Predators? A Test Involving Three Terrestrial Amphibians

Prey animals may enhance their fitness by avoiding predators, but unnecessary responses to predators that pose little threat may be maladaptive. Dietary cues from predators may be used by prey individuals to identify dangerous predators (i.e., those that have been feeding on conspecific prey), and consequently to minimize needless reactions to cues from innocuous animals. We tested for the presence of diet-mediated antipredator responses in a terrestrial system involving wandering garter snake predators (Thamnophis elegans) and amphibian prey (spotted frogs, Rana luteiventris; long-toed salamanders, Ambystoma macrodactylum; and Pacific tree frogs, Pseudacris regilla). Wild-caught prey were exposed to cues from predators fed heterospecific (worm) versus conspecific diets in two-sided behavioral arenas, and patterns of selection for particular sides of the arena were assessed. We found that none of the amphibian prey species responded to differences in the diet of their predator, but two species avoided cues associated with injured conspecifics. These results suggest that some amphibians lack the capacity to distinguish between dangerous and safe predators, possibly due to historically low levels of predation, or because their predators possess the ability to break down or mask cues allowing for such discrimination. However, given that our experimental protocol tested for a single metric of predation risk reduction (i.e., behavioral avoidance), further analyses will be required to determine whether diet-dependent antipredator behavior is largely absent from this predator-prey system. © 2005 by The Herpetologists\u27 League, Inc