Effects of predator diet and prey vulnerability on responses of larval amphibians to perceived predation risk

Prey from a wide range of taxa are known to display phenotypic plasticity when exposed to predators. Such predators can induce changes across a broad spectrum of behavioural, morphological and life history traits that ultimately can influence individual fitness. Responding to predators can be costly for the prey, thus prey should respond more strongly to predators posing increased threat. Predator diet likely is a good indicator of predation risk, as evidenced by studies showing that prey tend to respond more strongly to predators fed conspecifics than heterospecifics. However, the extent to which prey discriminatory abilities are finely-tuned is unclear, and additional research is needed to fully understand the ecological significance of diet in prey responses to perceived predation risk. I evaluated which of two closely-related frog species (bullfrog: Rana catesbeiana, mink frog: Rana septentrionalis ) suffered a higher predation from an odonate predator (dragonfly: Aeshna spp.). I also tested behavioural and morphological responses of tadpoles of either species to dietary cues from predators fed conspecific Rana, heterospecific Rana, heterospecific Libellulidae, or no predators (control). Such a design should enable me to see how baseline risk shapes the intensity of antipredator responses. Both species shared similar predation risk and reduced their activity when exposed to dragonflies fed conspecific or congeneric tadpoles; however increased sensitivity to conspecific predator diet was not observed. Bullfrogs exhibited morphological responses to perceived predation risk by growing larger than control tadpoles when exposed specifically to a mink frog diet. Mink frog tadpoles failed to exhibit comparable changes in morphology. Results from this experiment imply that selective pressures favouring antipredator responses may focus on groups of similar prey rather than exclusively on conspecifics when there is a lack of differential predation risk experienced by prey.