Building a natural repellent: effects of varying alarm cue exposure on swim activity and spatial avoidance in an...

Techniques for using natural anti-predator cues to guide the movements of animals and reduce human-wildlife conflict are highly desired. With continuous use, sensory adaptation, habituation and adaptive behavioural changes often reduce the efficacy of sensory deterrents. Theory suggests responses can be maintained with application practices that modulate the stimulus in time (on/off) or by continuously varying stimulus intensity. In aquatic environments, damage-released alarm cues from injured conspecifics are a reliable source of information regarding predation risk that can be used to guide the movements of invasive fishes. We used sea lampreys, Petromyzon marinus, drawn from an invasive population, to investigate whether modulating alarm cue exposure (on/off) or varying cue concentration during continuous exposure (low/high) would forestall predicted declinations in swim activity and spatial avoidance. We found that continuous exposure to alarm cue at a fixed concentration resulted in the predicted decline in swim activity. Modulating odour exposure timing (on/off) partially prevented response declination in swim activity, whereas varying odour concentration (low/high) fully prevented the reduction. We did not observe the previously reported habituation of the spatial avoidance response, likely due to the use of a small high-throughput assay system. Our results suggest modulating alarm cue exposure by varying odour concentration to prevent response declination holds promise as a management practice. Moreover, test systems for developing management practices should be carefully matched to the scale of the behavioural response being investigated.