Sensory compensation and its influence on predator detection, the interaction between chemical and visual information

Abstract

Fathead minnows, 'Pimephales promelas', have the ability to detect predators through visual, chemical and possibly mechanosensory cues. The predominant chemical cue used by minnows is alarm substance, a chemical released when the skin of a minnow is damaged. Previous research assumed that alarm substance was a pheromone designed to alert other members of the shoat of danger. If individuals sensed alarm substance, they were expected to react regardless of the context. Recent studies have created a controversy by demonstrating the response to alarm substance is dependent on the context (i.e., the level of risk) in which it is encountered. I propose that the response to alarm substance is not only determined by the level of risk, but also by the availability of information through the other senses. I developed a sensory compensation model that assumes the concentration of alarm substance necessary to generate an antipredator response decreases as the predation risk and the turbidity level increases. Two experiments were conducted to test the predictions of the model by manipulating the level of risk. The first experiment modified risk sensitivity with hunger levels and the second altered risk of predation through the availability of cover. (Abstract shortened by UMI.)