Fathead minnows, pimephales promelas, learn to recognize northern pike, esox lucius, as predators on the basis of chemical stimuli from minnows in the pike's diet


Predator recognition by naive prey may be facilitated if a predator's diet chemically 'labels' the predator. In laboratory experiments, naive fathead minnows, exhibited a fright response to chemical stimuli from unfamiliar predators, northern pike, that had recently eaten conspecific minnows, but not to chemical stimuli from the same predators that had eaten heterospecific prey (swordtails, Xiphophorous helleri). Minnows exposed to chemical stimuli from pike that had eaten conspecifics responded with a fright reaction to subsequent exposures, under identical conditions to the original exposure, to both tap water (a presumably neutral stimulus) and to chemical stimuli from pike that had eaten swordtails. However, when the minnows were re-tested in an experimental set-up that was different from that in the first exposure, they did not respond to the neutral stimulus but did exhibit a fright response to chemical stimuli from pike that had eaten swordtails. These results suggest that: (1) fathead minnows may initially recognize unfamiliar predators based solely on the predator's diet, (2) fathead minnows can learn to associate some characteristics of the stimulus introduction technique with a potentially dangerous situation, and (3) fathead minnows can learn to recognize the predator's chemical stimuli irrespective of the predator's recent feeding regime on the basis of the initial association between the predator's chemical stimuli and the stimuli from the minnows in its diet. These findings add a new mechanism for the learning of predator recognition.

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Animal Behaviour