Abstract
True bugs are generally considered to be well protected against bird predation. Sympatric species that have similar warning coloration are supposed to form a functional Mullerian mimetic complex avoided by visually oriented avian predators. We have tested whether these assumptions hold true for four species of European red-and-black heteropterans, viz. Pyrrhocoris apterus, Lygaeus equestris, Spilostethus saxatilis, and Graphosoma lineatum. We found that individual species of passerine birds differ in their responses towards particular bug species. Great tits (Parus major) avoided all of them on sight, robins (Erithacus rubecula) and yellowhammers (Emberiza citrinella) discriminated among them and attacked bugs of some species with higher probability than others, and blackbirds (Turdus merula) frequently attacked bugs of all the tested species. Different predators thus perceive aposematic prey differently, and the extent of Batesian-Mullerian mimetic complexes and relations among the species involved is predator dependent.
Highlights
Unpalatable animals usually use warning signals to discourage predators from attacking them
Our experimental birds were more likely to be experienced with P. apterus and G. lineatum than with L. equestris and S. saxatilis, because the latter two are closely associated with their host plants and, the distribution of these bugs is restricted
Individual species of passerine birds differed in their responses towards a particular bug species
Summary
Unpalatable animals usually use warning signals to discourage predators from attacking them. Several types of mimetic relationships between the species involved in the mimetic complex were distinguished, viz. Batesian, quasi-Batesian, quasi-Müllerian, Müllerian and super-Müllerian (Speed, 1999; Balogh et al, 2008) Their classification depends on the level of mutual similarity of the species involved and on presence, type and efficiency of their defensive mechanisms. Exnerová et al (2003a, 2007) showed differences among bird predators in reactions to aposematic prey; we can assume that mimetic complexes could be predator dependent. This may be the reason why the results of experiments performed with bird predators and living insect prey were ambiguous, as to the degree of similarity between the appearances of two aposematic species, which is required for their mutual protection (Evans et al, 1987 contra Sillén-Tullberg et al, 1982).
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