Antipredator defence in butterflies

Abstract: Predation exerts a potent selection mechanism and has resulted in a suite of antipredation adaptations encompassing morphological and behavioral traits in prey. In butterflies, several such traits appear to be directed towards birds which are considered as one of their major predators. In this thesis I have investigated tactics by which adult butterflies may survive close encounters with birds. In paper I, I provide supporting evidence that the small white “comma” on females of the comma butterfly, Polygonia c-album, has a distractive function on blue tits and so reduces the attack risk. In paper II & III, I investigate the antipredator efficiency of sudden wing-flicking in two species, the peacock butterfly, Inachis io, and the European swallowtail, Papilio machaon, when confronted with domestic fowl and great tits, respectively. Peacock butterflies were manipulated to either display visible or painted over eyespots. Interestingly, the birds that confronted peacocks with visible eyespots were more likely to utter antipredator alarm calls, which imply that the eyespots may be perceived as real eyes of a potential predator. On the whole, wing-flicking in both species typically induced evasion in the birds which suggests that the birds became frightened rather than perceiving the butterflies as not profitable to attack for some other reason. Moreover, I use blue tits as predators to investigate the possible function of smaller eyespots of satyrine butterflies in that they serve to divert predator attacks. Evidence suggests that low light conditions accentuated in the UV may enhance the deflective function of marginal eyespots in the woodland brown butterfly, Lopinga achine (paper IV). In paper V, I show that the presence of one marginal eyespot on the speckled wood butterfly, Pararge aegeria, can deflect bird attacks; moreover, when the butterfly is concealed against the background, eyespots can also increase the latency time until bird attack. In conclusion, my thesis underscores that behavioral studies of predators are instrumental to aid our understanding of the adaptive significance of certain behavioral and morphological traits in prey.