Acquired recognition of novel predator odour cocktails by juvenile glowlight tetras

Prey can learn to recognize novel predators through the association of aversive stimuli (visual or chemical) paired with a predator cue (i.e. acquired predator recognition). Previous studies have demonstrated that a variety of prey can readily learn the identity of a single predator. In this study, we examined whether predator-naïve glowlight tetras, Hemigrammus erythrozonus, could simultaneously acquire recognition of three novel heterospecific odours as predation threats, and whether this simultaneous learning confers a survival benefit. Tetras were conditioned to the odours of largemouth bass, Micropterus salmoides, convict cichlids, Archocentrus nigrofasciatus, and comet goldfish, Carassius auratus, simultaneously, then subsequently tested 48 h later for learned recognition of each odour individually. Tetras were also tested for the recognition of yellow perch, Perca flavescens, a novel predator, to assess whether learned recognition is generalized. Tetras significantly increased antipredator behaviour when exposed to each of the conditioned predator odours and the nonpredator goldfish odour, but not to perch odour (i.e. not different from the distilled water control). These results demonstrate acquired recognition and not a generalization to novel predator odours. Subsequent staged encounters with live pumpkinseed sunfish, Lepomis gibbosus, predators showed that tetras conditioned to either sunfish odour alone or multiple odours increased survival over unconditioned tetras. These results are the first indication that prey possess the ability to learn the cues of multiple predators simultaneously, and that this multiple learning provides a survival benefit.