Asymmetry in size, shape, and color impairs the protective value of conspicuous color patterns

Abstract

The received view of protective coloration in animals is that conspicuous colors and patterns have evolved because they elicit avoidance behavior in potential predators. In the present study, we examine the spontaneous response of naive predators (Gallus gallus domesticus) to artificial prey to test the hypothesis that deviations from bilateral symmetry of signaling pattern elements may negatively influence the avoidance-inducing effect of conspicuous color patterns. Chicks displayed stronger aversions to artificial ‘‘butterfly’’ prey items possessing symmetric color pattern elements than to those possessing asymmetric signals with pattern elements of different color or shape. Although they attacked signals with a size asymmetry of 5% at the same rate as symmetric signals, signals with a size asymmetry of 7.5% or more were attacked more often than were symmetric signals. These results suggest that the protective value of conspicuous color patterns is impaired by asymmetry in color, shape, and size of color pattern elements. Our findings also argue against the notion that animals have inherent preferences for symmetric over asymmetric objects, and demonstrate the existence of a threshold for asymmetry detection, beyond which further increments in asymmetry have no influence on signal efficacy. Key words: asymmetry, communication, perception, predation risk, signaling. [Behav Ecol 15:141–147 (2004)]