Nutritional Plasticity In Gray Treefrogs: Interactions Between Competition And Predation Threat

Anurans utilize digestive tradeoffs to best survive in their environment, often in response to competition and predation pressure. In some larval anurans, intraspecific competition induces longer guts, providing a digestive advantage under limiting resources. However, predation threat can induce deeper tails and associated shorter guts in larvae. The purpose of this study was to describe nutritionally plastic responses of larval eastern gray treefrogs, Hyla versicolor, reared with simultaneous environmental stressors: predation and competition. Specifically, we asked if larval guts lengthen to increase digestive efficiency or will tail morphology change to better evade predators? H. versicolor larvae were reared in 410 L mescocosms with and without a caged dragonfly nymph (Anax sp.) predator. Anax sp. predators were fed five H. versicolor hatchings daily to generate kairomones (chemical cues) in the larval environment. Larvae were maintained at 10 individuals and 60 individuals per tank to provide varying levels of competition. Larvae reared at high-density developed longer guts than those reared at low density. Predation threat did not influence gut length. Predation did induce smaller livers and deeper tails in larvae, but did not hinder growth. These differences suggest that larvae have lower fat stores when they grow larger tails, or they could also forage less in the presence of a predator. These effects in the larval stage may have important consequences post-metamorphosis and should be a focus of future research