Time-sensitive neophobic responses to risk

Abstract

Prey animals that experience a high background level of risk are known to exhibit considerable phenotypic plasticity in their responses to unknown predators. When background risk is high, prey exhibit neophobic responses to unknown odours, i.e. they show a fear response to any new stimulus. Here, we examine whether temporal variation in the pattern of risk to which prey are exposed influences neophobic responses. To establish prey groups with different temporal patterns of risk, embryonic woodfrogs (Lithobates sylvaticus) were exposed to conspecific alarm cues each morning and control cues in the evening, or conspecific alarm cues each evening and control cues in the morning, for their entire embryonic period. After the tadpoles hatched they were tested at both times of day for known risk cues (alarm cues), unknown predator odours or water control. Tadpoles responded to alarm cues at any time of day, but showed neophobic responses to predator odours only if their test time matched their embryonic risk exposure time. These results demonstrate a high level of sophistication of neophobic responses and points to temporal variation in risk as a key driver of antipredator decision making.