Acquired Recognition of Chemical Stimuli from Pike, Esox lucius , by Brook Sticklebacks, Culaea inconstans (Osteichthyes, Gasterosteidae)

In this study we test whether brook sticklebacks ( Culaea inconstans ) can acquire predator recognition through releaser‐induced recognition learning, i.e. simultaneous exposure to aversive ('releasing') stimuli and neutral stimuli causing learned aversion to the neutral stimuli. We exposed wild‐caught pike‐naive brook sticklebacks (collected from a creek containing fathead minnows, Pimephales promelas , but not pike, Esox lucius ) to chemical stimuli from pike that were mixed with brook stickleback skin extract, fathead minnow skin extract, or a control of distilled water. In subsequent tests 2 d later, when only pike stimuli were presented, sticklebacks conditioned with stickleback skin extract and fathead minnow skin extract exhibited antipredator behaviour (i.e. increased schooling and movement toward the substrate), while those conditioned with distilled water did not. Sticklebacks conditioned with stickleback skin extract responded to pike with a more intense response, in terms of movement toward the substrate, than those conditioned with fathead minnow skin extract, suggesting that conspecific skin extract may be a stronger stimulus than heterospecific skin extract for learning recognition of predators. To our knowledge this is the first study to demonstrate that an acanthopterygian fish can acquire predator recognition through the pairing of conspecific alarm pheromone with the cue of a predator. Furthermore, our results are the first to demonstrate that fish can acquire predator recognition through the pairing of a heterospecific alarm pheromone with the cue of a predator. These results suggest that brook sticklebacks will benefit by being in close proximity to fathead minnows. Acquired predator recognition has long‐term consequences in mediating predator‐prey interactions.