Quantifying the success of prey crypsis, aposematism and evasiveness in avoiding avian predators’ attack

Antipredator defences typically act at specific stages along the predation sequence, i.e., during prey encounter, identification, approach, and subjugation. However, the effectiveness of such defences has seldom been contrasted and quantified in parallel using an experimental setting with wild predators.

Within aviaries installed in two localities in northeastern Peru, we recorded the responses of avian predators to three antipredator defences, crypsis, aposematism and evasiveness, each expressed in three butterfly species. We examined both immature and adult birds from forest and urban environments, including species having diets ranging from fully insectivorous to omnivorous.

We confirmed the expectations that cryptic butterflies (Nymphalidae: Satyrinae: Euptychiina) largely remained undetected, whereas aposematic Heliconius (Nymphalidae: Heliconiinae) were frequently noticed but seldom attacked. Evasive Spicauda (Hesperiidae: Eudaminae) were frequently detected and attacked but exhibited higher evasion rates likely owing to their fast flight.

Bird life stage dramatically influenced defence effectiveness. Immature birds were more prone to attacking Heliconius , possibly due to being in early learning stages of local aposematic cues. We also found evidence that predation pattern differs between bird families, making more adept predators more likely to attack defended prey (i.e., Vireonidae).

Our findings illuminate the nuanced dynamics of predator-prey interactions in complex tropical environments, highlighting the intricate behavioural responses of wild predators and how they shape the co-existence of diverse antipredator defences.