The role of latent inhibition in acquired predator recognition by fathead minnows

The ability of prey animals to recognize and respond to potential predators has important survival consequences. In many predator–prey systems, prey need to learn which species are potential predators. Consequently, selection should favour efficient learning mechanisms. For aquatic organisms, a very effective way to learn to identify potential predators is by associating cues of injured conspecifics with cues of an unknown predator. To our knowledge, no studies of fishes have failed to show successful acquisition of predator recognition using this learning method. The goal of our study was to begin to address the limits of this learning paradigm. Specifically, we tested whether pre-exposure to a novel predator would prevent the associative learning from occurring. In the first treatment, we pre-exposed minnows to distilled water for 1 h on 5 consecutive days and then conditioned them with conspecific skin extract paired with charr odour. In the second treatment, minnows were pre-exposed to charr odour and conditioned with conspecific skin extract paired with charr odour. In the last treatment, minnows were pre-exposed to charr odour but “conditioned” with distilled water paired with charr odour. When tested for recognition of the charr odour alone, only the fish that were not pre-exposed to charr odour showed responses to the predators. We conclude that latent inhibition affects the efficiency of associative learning of the predator.