Predator Recognition and Avoidance in the San Marcos Salamander
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Selection by predators is among the most important forces acting on prey populations. To persist with predators, prey must be able to recognize and respond to predatory threats. Despite the benefits of avoidance, there are time allocation tradeoffs with foraging and mating that make excessive responses to predators costly. Thus, antipredator behaviors of prey are often the result of complex interactions of effectiveness and efficiency. The San Marcos salamander (Eurycea nana) is a fully aquatic salamander endemic to the headwaters of the San Marcos River. Eurycea nana is subject to predation by a diverse community of native and nonnative fish predators. Despite the importance of predation pressures on prey populations and the protected status of E. nana and other regional congeners, no studies had examined predator-prey interactions in these species. This research was aimed at elucidating the mechanisms by which E. nana recognizes and responds to predators. Specifically, I examined recognition of native and nonnative predators, predation risk assessment via predator diet cues and cues of damaged conspecifics, and how experience with predators affects avoidance behaviors. I found that E. nana use chemical stimuli to detect predators and respond to predators by decreasing activity levels. These salamanders innately recognize some predators, including nonnative species that are closely related to native predators, but experience with predators can alter the intensity of avoidance responses. These studies provided insight into the mechanisms by which E. nana recognizes predators. Additionally, I conclude that repeated exposures to predators can enhance avoidance behaviors exhibited by prey. In sum, these studies highlight the need for research exploring the plasticity of avoidance behaviors in prey that innately recognize and respond to predators.