Learning about danger: chemical alarm cues and local risk assessment in prey fishes

An individual's behaviour patterns can be conceptualized as a series of threat‐sensitive trade‐offs between ambient predation pressure and a suite of fitness‐related activities, such as resource defence, foraging and mating. Individuals that can reliably assess local predation risk could increase their fitness potential by exhibiting predator avoidance behaviours only at appropriate times. However, such learned risk assessment requires reliable information regarding current predation risks. A diverse range of prey fishes are known to possess chemical alarm cues, which when detected by conspecifics and some heterospecifics, elicit a variety of overt and covert responses. These chemical cues, either alone or as a part of a predator's dietary odour, provide reliable information regarding local predation risk. In this review, I describe recent works examining the role of chemosensory information in: (i) acquired predator recognition, (ii) predator inspection behaviour and (iii) the use of conspecific and heterospecific cues as social information sources.