A test of the species confidence hypothesis in dusky damselfish.

Visual cues are important in both interspecific and intraspecific communication. The species confidence hypothesis proposes that animals are more attracted to conspecific colors and repelled by colors, not on their bodies. Studies on terrestrial lizards and birds have tested the species confidence hypothesis and shown that conspecific colors elicit reduced antipredator behavior. To date, the species confidence hypothesis has not been tested in the marine environment, specifically on coral reefs where color communication is of vital importance. We addressed this knowledge gap by measuring flight initiation distance (the distance an individual moves away from an approaching threat) in dusky damselfish ( Stegastes nigricans ) in response to an approaching disc of 1 of 4 different color treatments: conspecific, blue, yellow, and black. If the species confidence hypothesis explained variation in damselfish flight initiation distance, then we expected individuals to tolerate closer approaches when approached by a conspecific color. In addition, we calculated the color difference between each stimulus and its corresponding background as a potential alternative explanation for flight responses. Damselfish tolerated the closest approach from the conspecific color stimulus; there were no significant differences between other colors and there was no support for the alternative color difference hypothesis. As with similar terrestrial studies, these results are relevant to ecotourists' choice of swimsuit and wetsuit colors because color choice may modify natural antipredator behavior.