Risk assessment via predator diet cues in a coral reef goby

Recent studies conducted in freshwater systems have shown that predator faeces can provide important chemosensory information to prey individuals. To date, no studies on the ability of prey to assess risk through predator diet cues have been undertaken in coral reef ecosystems. Therefore, the present study investigated whether the conspecific chemical cues of a coral reef goby (Asterropteryx semipunctatus) elicited an antipredator response once they had passed through the gut of a common piscivore (the rock cod, Cephalopholis boenak). Predators were fed one of two different diets: A. semipunctatus or Xiphophorus helleri for three consecutive days. Acclimated A. semipunctatus were then exposed to: faecal cues containing digested A. semipunctatus or X. helleri; conspecific chemical cues; X. helleri chemical cues; and seawater. A significant reduction in moves and feeding strikes was observed in response to the faeces containing conspecifics, compared to those containing X. helleri. This change in behaviour was of a similar magnitude to that exhibited towards the conspecific chemical cue, suggesting that a key component of the cue may not completely degrade during the digestion process. This is the first study to document behavioural responses to predator faeces in a coral reef fish, highlighting the effectiveness of diet cues as a method of risk assessment.