How Do Predators Learn to Recognize a Mimetic Complex: Experiments with Naive Great Tits and Aposematic Heteroptera
Abstract
We tested the importance of innate wariness, avoidance learning, memory and generalization for the formation of predatory behaviour in naive great tits (Parus major) towards mimetic complex of four aposematic species of true bugs (Insecta: Hemiptera: Heteroptera): Lygaeus equestris, Spilostethus saxatilis, Pyrrhocoris apterus and Graphosoma lineatum. The birds showed almost no innate wariness against the aposematically coloured bugs, although a hidden wariness elicited by defensive chemicals of some of the bug species is not excluded.
Naive birds learned to avoid different species at different rates, which resulted in different prey mortalities. The avoidance learning was faster when the defensive chemicals produced an immediate irritating effect (particularly when squirted into distance - G.lineatum) than when they caused sickness several minutes after the consumption (P.apterus).
The experience of birds from learning to avoid a particular species of bug affected their subsequent behaviour to other species - experience with better-defended species resulted in longer attack latencies, more cautious attacks, broader generalization and lower prey mortality. The least defended species, P.apterus, benefited from the experience of birds with better-defended species, whereas the birds' experience with P.apterus did not reduce mortality risk of the other species comparably.
Judging from the inexperienced young birds, the mimetic relationships are likely to be quasi-Batesian. However, as wild-caught great tits avoid all the four species to the same extent, the relationships may become more mutualistic (quasi-Mullerian) in later phases of learning under natural conditions.
The relationships among species in the mimetic complex thus seem to depend on the amount of experience of the bird predators.