Prey survival by predator intimidation: an experimental study of peacock butterfly defence against blue tits

Presented peacock butterflies to blue tits with eyespots either intact or painted over, and with the sound-producing wing hiss either intact or prevented, and recorded whether the bird attacked and whether the butterfly survived.

Studied in

Aglais io, Cyanistes caeruleus

Sample size

butterflies presented to blue tits with eyespots painted out or intact

Butterflies with intact eyespots survived far more often than those whose eyespots were painted out. The wing hiss contributed additionally but the visual display accounted for most of the effect.

• Captive birds in an enclosure, presented with butterflies rather than finding them.
• One butterfly species and one predator species.
• Painting over eyespots removes conspicuousness as well as eye-likeness, so this design alone cannot separate them.

• Painting out the spots

  Peacock butterflies flash large eyespots when disturbed. Does the display actually stop a bird attacking, or merely delay it?

• Eyespots

  Butterfly eyespots do deter birds — but apparently not by looking like eyes. When conspicuousness and eye-likeness were varied separately, equally conspicuous bars and squares protected prey just as well as circles.