Linking predator risk and uncertainty to adaptive forgetting: a theoretical framework and empirical test using tadpoles.

Hundreds of studies have examined how prey animals assess their risk of predation. These studies work from the basic tennet that prey need to continually balance the conflicting demands of predator avoidance with activities such as foraging and reproduction. The information that animals gain regarding local predation risk is most often learned. Yet, the concept of 'memory' in the context of predation remains virtually unexplored. Here, our goal was (i) to determine if the memory window associated with predator recognition is fixed or flexible and, if it is flexible, (ii) to identify which factors affect the length of this window and in which ways. We performed an experiment on larval wood frogs, Rana sylvatica, to test whether the risk posed by, and the uncertainty associated with, the predator would affect the length of the tadpoles' memory window. We found that as the risk associated with the predator increases, tadpoles retained predator-related information for longer. Moreover, if the uncertainty about predator-related information increases, then prey use this information for a shorter period. We also present a theoretical framework aiming at highlighting both intrinsic and extrinsic factors that could affect the memory window of information use by prey individuals.