Resemblance to the Enemy's Eyes Underlies the Intimidating Effect of Eyespots.

Eyespots of some prey are known to deter predators, but the reason for this response has not yet been established, and thus the taxonomically widespread occurrence of this color pattern has remained an evolutionary conundrum. Two alternative hypotheses propose that (1) the eyelike appearance of the pattern falsely indicates the presence of the predator's own enemy or (2) predators are hardwired to be cautious toward conspicuous prey. Earlier research has pertained mainly to eyespots in butterflies. Here we tested the hypothesis that eyespots resemble eyes by utilizing the lateral position of eyes in fishes. This allowed us to produce eyelike displays that did not have the round appearance of eyespots. Our study indicates that eye mimicry is an important factor evoking hesitation in predators. Moreover, we present direct evidence that this is because predators associate eyelike displays with the threat posed by their own enemies.