Threat sensitivity in the San Marcos salamander: effects of predator diet and prey experience

Prey must constantly balance foraging and predator avoidance demands. Avoidance response efficiency may be improved when prey match the intensity of their avoidance behaviours to a perceived level of predatory threat (threat sensitivity). Additionally, experience with predators may influence the intensity of avoidance responses. I examined the possibility that experience with predators in the natural habitat would influence threat sensitive avoidance behaviours of an aquatic salamander, Eurycea nana, by comparing the intensity of avoidance responses to predators that had been fed a neutral diet (low-risk) or a diet of conspecifics (high-risk) between laboratory-reared and recently-collected adult salamanders. I found that laboratory-reared salamanders exhibited graded responses to low- and high-risk predators consistent with threat-sensitive predator avoidance. Predator-experienced salamanders (recently-collected), however, responded less intensely to all predators and their responses showed little evidence of threat sensitivity. These less intense responses observed in experienced salamanders may result from mechanisms of adaptive forgetting, which allow prey to respond to environmental variation. I discuss implications of these results for E. nana and other prey as well as highlighting the need for researchers to consider the longer-term experiences of prey used in studies of predation risk.