Olfactory sensitivity and threat-sensitive responses to alarm cue in an invasive fish

Abstract

AbstractEstablishing how invasive animals perceive and manage the threat of predation improves our understanding of why certain species rapidly invade unfamiliar environs where others do not. The threat-sensitive response hypothesis predicts that prey that modulate their antipredator behavior in response to the perceived intensity of the threat will have a selective advantage. We investigated the behavioral and olfactory antipredator responses of migrating invasive sea lamprey to varying concentrations of a conspecific alarm cue in the laboratory and field. We hypothesized the odor indicates the presence and location of predation risk on river shorelines, allowing sea lamprey to either alter their migratory path and/or movement timing to reduce exposure to the predator. Migratory sea lampreys exhibited threat-sensitivity in space-use both in the laboratory and nature by increasingly avoiding areas as the concentration of alarm cue increased when safe space was available (areas without the alarm cue). The intensity of the avoidance at higher concentrations was greater in the field. Electrophysiological recordings from the olfactory organ confirmed a concomitant increase in signal output to the olfactory bulb of the brain when exposed to increased alarm cue concentrations. However, increasing the alarm cue concentration did not alter the animal’s motivation to move upstream in either avoidable risk or unavoidable risk scenarios. Exposure to alarm cue affected decisions regarding how to move, but not whether to move. Knowledge of how the animal uses the cue in nature reveals ways to use the cue to manipulate movement and achieve conservation goals.