Threat-sensitive predator avoidance by slimy sculpins: understanding the importance of visual versus chemical information

Abstract

The supposition that prey animals assess and behave flexibly in response to different degrees of predation threat is known as the threat-sensitive predator avoidance hypothesis. We completed a series of field and laboratory experiments to examine whether slimy sculpins (Cottus cognatus) exhibit threat-sensitive predator avoidance when exposed to sympatric predatory brook trout (Salvelinus fontinalis). In a field experiment we caged small and large trout in similar habitats and found that sculpins avoided areas containing trout that were large enough to pose a threat to them, but did not avoid areas containing trout that were small and hence not a threat. In a series of laboratory experiments we found that sculpins showed threat-sensitive predator avoidance when they could assess the predator visually. However, when only chemical cues from the predator were presented, sculpins responded to the predator regardless of its size. Chemical cues seem to function to warn the sculpin that the predator is in the vicinity, but visual cues are needed in order to accurately assess the risk posed by the predator.