Fathead Minnows Learn to Recognize Heterospecific Alarm Cues They Detect in the Diet of a Known Predator

Abstract

A wide diversity of animals release chemical cues when attacked by a predator. Often these chemicals serve to warn other conspecifics, and in some cases heterospecifics, of danger, and hence have been termed alarm cues. Responses of animals to alarm cues produced by other species often need to be learned, yet mechanisms of learned recognition of heterospecific cues are not well understood. We tested whether fathead minnows (Pimephales promelas) could learn to recognize heterospecific alarm cues when they detected the cues in the diet of a known predator. We exposed fathead minnows to chemical stimuli collected from a known predator, northern pike (Esox lucius) fed one of two unknown prey, stickleback (Culaea inconstans) or swordtails (Xiphophorous helleri). In subsequent tests, the minnows were exposed to either swordtail skin extract or stickleback skin extract. We found that minnows that were initially exposed to the pike fed stickleback subsequently responded to stickleback skin extract with an anti-predator response but did not respond to swordtail skin extract. Likewise, minnows that were initially exposed to the pike fed swordtails subsequently responded to swordtail skin extract with an anti-predator response but they did not respond to stickleback skin extract. These results clearly demonstrate that minnows learn the identity of heterospecific alarm cues when they detect those cues in the diet of a known predator. Learned recognition of heterospecific alarm cues has important implications for predator/prey interactions.