The effects of pattern symmetry on detection of disruptive and background-matching coloration

Abstract

Two, logically distinct but sometimes compatible, mechanisms of camouflage are background-matching and disruptive coloration. In the former, an animal's coloration comprises a random sample of the background, and so target–background discrimination is impeded. In the latter, object or feature recognition is compromised by placing bold, high-contrast colors so that they break up the prey's body into apparently unconnected objects. Recent experimental evidence for the utility of disruptive colors, above and beyond that conferred by background matching, has been based on artificial prey with patterns lacking a plane of symmetry. However, it is plausible that the bilateral symmetry present in natural prey may compromise the efficiency of disruptive coloration, on account of the potency of symmetry as a cue in visual search. In this study, we tested this prediction in the field, by tracking the “survival” under bird predation of artificial mothlike targets placed on oak trees. These had background-matching color patches placed either disruptively or nondisruptively and with or without bilateral symmetry. We found that symmetry reduced the effectiveness of both nondisruptive and disruptive background-matching coloration to a similar degree so that the negative effects of symmetry on concealment are no greater for disruptive than nondisruptive patterns.