Responses of Foothill Yellow-legged Frog (Rana boylii) Larvae to an Introduced Predator

Abstract

The consequences of species introductions into non-native habitats are a major cause for concern in the U.S. Of particular interest are the effects of predation by introduced fishes on native amphibian communities. We sought to determine whether Foothill Yellow-legged Frog (Rana boylii) larvae could recognize non-native Smallmouth Bass (Micropterus dolomieu) as a predatory threat. Through a series of laboratory experiments, we examined the initial and overall behavioral responses of larvae to native predators (Rough-skinned newts, Taricha granulosa), introduced predators (M. dolomieu), and native non-predatory fish (Speckled Dace, Rhinichthys osculus). Each experiment examined a different potential mode of detection including chemical cues; visual cues; or a combination of chemical, visual, and mechanical cues. Initially, larvae of R. boylii responded with an increase in activity levels when exposed to visual cues of M. dolomieu. Analyses of overall responses suggested that individual larvae of R. boylii require multiple cues to facilitate predator detection. When exposed to multiple cues of their native predator, larvae responded with a significant reduction in activity levels. Those larvae exposed to cues of the non-native predator displayed similar behaviors relative to control cues. Consequently, larvae of R. boylii appear to be especially vulnerable to predation by non-native M. dolomieu.