Risk-sensitive information gathering by cyprinids following release of chemical alarm cues

Abstract

In aquatic environments, chemical cues released during a predator attack reliably inform prey about the presence of predation risk. Prey with information about predation risk are more successful in surviving encounters with predators than are unwary prey. To remain prepared for attack, prey should continue to monitor the status of predation risk, presenting a behavioural trade-off for prey: increased distance from areas labelled with alarm cues reduces exposure to predation risk but also reduces access to information about predation risk. In two laboratory experiments we used the presence and absence of water flow in a laboratory fluvarium to test alarm response and subsequent risk-sensitive information gathering by zebrafish (Danio rerio). In response to chemical alarm cues, fish significantly reduced activity and increased use of shelters. In the absence of flow, fish sought out the shelter nearest the cue source. In the presence of flow, fish preferred to seek shelter downstream, but not upstream, of the cue source. This allowed fish to gather information about predation risk from a relatively safe distance. In a field experiment on natural populations of stream fishes, fish avoided areas where chemical alarm cues were released (versus blank water control) but primarily because they avoided the region immediately upstream of the cue source. Fish use of the area immediately downstream of cue release did not decrease. Taken together, these laboratory and field data are consistent with a trade-off between risk avoidance and information gathering.