Great tits (Parus major) searching for artificial prey: implications for cryptic coloration and symmetry

It has been suggested that bilateral symmetry may impose a cost for animals relying on camouflage because symmetric color patterns might increase the risk of detection. We tested the effect of symmetry on crypsis, carrying out a predation experiment with great tits (Parus major) and black-and-white–patterned, artificial prey items and background. First, we found that detection time was significantly longer for a highly cryptic, asymmetric pattern based on a random sample of the background than for its symmetric variants. Second, we were able to arrange the elements of a prey pattern in a way that the resulting asymmetric pattern was highly cryptic and, furthermore, its symmetric variant was highly cryptic as well. We conclude that symmetry may impose a substantial cost on cryptic patterns, but this cost varies among patterns. This suggests that for prey, which predators typically view from an angle exposing their symmetry, selection for pattern asymmetry may be less important and selection for decreased detectability cost of symmetry may be more important than previously thought. This may help to understand the existence of so many prey with cryptic, symmetric color patterns.