Behavioural response of Dryophytes plicatus tadpoles to the cues of non-native rainbow trout and a native snake

Non-native species have numerous and significant, often negative, effects on amphibians, but that threat may be ameliorated if the native species is able to respond behaviourally to the non-native predators. We experimentally compared the behavioural response of tadpoles of the Ridged Tree Frog, Dryophytes plicatus, to cues from non-native Rainbow Trout, Oncorhynchus mykiss, to those to a native predator, the Short-tail Alpine Garter Snake, Thamnophis scaliger. Dryophytes plicatus tadpoles did not alter activity in response to cues from O. mykiss but increased activity in the presence of cues from T. scaliger, although it is possible this increase is related, at least in part, to the order of the presentation of the cues. The activity of D. plicatus tadpoles was higher in the absence of the vegetation than in its presence when exposed to predator cues, both T. scaliger and O. mykiss, but not in the control. In conclusion, our results show D. plicatus tadpoles alter their overall activity when exposed to cues from a native predator, T. scaliger, but not the non-native O. mykiss. These results may explain, in part, why D. plicatus can co-occur with T. scaliger but not O. mykiss.