Predation risk assessment and the anti-predator behavioral dynamics of larval anurans.

Abstract

While the anti-predator behavior of prey and its effects have been well-studied, how prey actually use the information available to them to assess the level of predation risk and how their perceived risk interacts with other factors to determine their behavior have not. Using a system of predatory larval dragonflies (<italic>Anax</italic> spp.) and larval anurans (green frog, <italic>Rana clamitans</italic>, and wood frog, <italic>Rana sylvatica</italic>, tadpoles), I studied how prey use the information available to them to assess the current level of predation risk, how their perceptual ability influences the accuracy of their risk assessment, and how several factors beside their perceived risk influence their behavior. First, I used behavioral observations (activity level) to estimate the level of risk that green frog tadpoles assess during exposure to <italic>Anax</italic> chemical cue, and showed that their prior experience can influence their risk assessment. Second, I showed that green frog tadpoles are unable to detect the age of <italic>Anax</italic> chemical cue upon cue exposure. I also showed that they may misestimate the spatial distribution of <italic>Anax</italic> through their assessment of the <italic> Anax</italic> chemical cue landscape. Third, I showed how the circadian feeding rhythm of green frog tadpoles and their energetic state can influence their behavioral response to a level of perceived risk. Finally, I show that several of the same processes operate in the risk assessment of wood frog tadpoles, but that wood frog tadpoles may respond differently to a level of perceived risk because of differences between the life history strategies of green frogs and wood frogs. My results suggest that: (1) research on predation risk assessment should focus on characterizing the information available to prey, but with attention given to the context in which prey encounter the information and the limitations in their ability to accurately assess it, and (2) at any point in time, a prey's behavior is a function of the history of the predator-related information available to it, which can be consolidated into its perceived predation risk, and of its state at that time (e.g. its energetic state).