Early life experience with predators impacts development, behavior, and post-translocation outcomes in an endangered amphibian

Abstract

Pre-release training is becoming a standard practice in conservation breeding and translocation programs for mammals and birds, but is still relatively neglected for herpetofauna, likely stemming from widespread beliefs that amphibians are “hard-wired” and are thus predicted to benefit little from experiential learning. However, experience during development can drive both morphological and behavioral modifications that could benefit post-translocation survival. Here, we developed an anti-predator training program for the endangered mountain yellow-legged frog Rana muscosa and evaluated its impact on morphometrics, developmental rates, behavior, and post-release outcomes. Using a controlled, balanced factorial experimental design, we exposed individuals at two developmental stages (tadpoles and post-metamorphic) to visual and olfactory cues from one of its principal predators, the two-striped garter snake Thamnophis hammondii. We found that exposure to predators during the tadpole stage impacted tadpole development, morphology, and behavior. However, we found no evidence that post-metamorphic behavior or post-release outcomes were influenced by tadpole predator exposure, either on its own or in interaction with post-metamorphic training treatments. Training of post-metamorphic frogs, however, yielded evidence of learning, with downstream effects on behavior and apparent survival after release into the wild. Our findings produce novel insights on the value of anti-predator training in amphibian conservation translocation programs, bolster recent evidence re-evaluating the importance of learning and developmental experience for amphibian species, and provide guidance for selecting optimal developmental windows for training.