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Abstract:
In freshwater environments, chemosensory cues play an important role in predatorprey
interactions. Prey use a variety of chemosensory cues to detect and avoid predators.
However, whether predators use the chemical cues released by disturbed or stressed
prey has received less attention. Here we tested the hypothesis that the disturbance
cue cortisol, in conjunction with visual cues of prey, elevates predatory behavior.
We presented predators (perch, Perca fluviatilis) with three chemosensory choice tests
and recorded their location, orientation, and aggressive behavior. We compared the
responses of predators when provided with (i) visual cues of prey only (two adjacent
tanks containing sticklebacks); (ii) visual and natural chemical cues of prey vs. visual
cues only; and (iii) visual cues of prey with cortisol vs. visual cues only. Perch spent a
significantly higher proportion of time in proximity to prey, and orientated toward prey
more, when presented with a cortisol stimulus plus visual cues, relative to presentations
of visual and natural chemical cues of prey, or visual cues of prey only. There was a trend
that perch directed a higher proportion of predatory behaviors (number of lunges)
toward sticklebacks when presented with a cortisol stimulus plus visual cues, relative
to the other chemosensory conditions. But they did not show a significant increase
in total predatory behavior in response to cortisol. Therefore, it is not clear whether
water-borne cortisol, in conjunction with visual cues of prey, affects predatory behavior.
Our results provide evidence that cortisol could be a source of public information about
prey state and/or disturbance, but further work is required to confirm this.
