The protective value of conspicuous signals is not impaired by shape, size, or position asymmetry

Various conspicuous signals in nature promote initial and learnedavoidance by predators. It is widely thought that such signalsare most effective when highly symmetrical in features suchas size and shape, supported by recent laboratory experimentswith domestic chicks and artificial prey. However, no studyhas investigated the effect of asymmetry on conspicuous signalsin a natural setting, where viewing distances, angles, predatorspecies, and light conditions vary and where predators encounterprey sequentially rather than simultaneously. We undertook 2field experiments with artificial gray-scale prey, marked witha pair of white markings presented to wild avian predators,to test the effect of asymmetry on the survival value of conspicuoussignals in the field. Experiment 1 had treatments with symmetricalspots or with spots asymmetrical in area between 5 and 50%.All marked treatments survived better than unmarked controls,but there was no benefit of being symmetrical. Experiment 2tested the effect of possessing markings asymmetrical for shapeor position and any additive effect of these 2 features. Again,symmetry conferred no benefit and targets with markings asymmetricalfor position and/or shape survived equally well as those withsymmetrical arrangements. These findings indicate that asymmetryin warning signals may not be costly to prey in nature or beof less importance compared with other features of the signal,such as color and overall size.