Behav Ecol Sociol DOI 10.1007/s00265-005-0069-9 ORIGINAL ARTICLE Adrian Vallin . Sven Jakobsson . Johan Lind . Christer Wiklund Crypsis versus intimidation—anti-predation defence in three closely related butterflies Received: 23 November 2004 / Revised: 11 July 2005 / Accepted: 25 July 2005 # Springer-Verlag 2005 Abstract Butterflies that hibernate exhibit particularly effi- cient defence against predation. A first line of defence is crypsis, and most hibernating butterflies are leaf mimics. When discovered, some species have a second line of de- fence; the peacock, I. io, when attacked by a predator flicks its wings open exposing large eyespots and performs an intimidating threat display. Here we test the hypothesis that butterflies relying solely on leaf mimicking and butterflies with an intimidating wing pattern, when attacked, exhibit different behavioural suites—because leaf mimicking is best implemented by immobility, whereas intimidating coloration is best implemented by intimidating behaviour. In laboratory experiments blue tits, Parus caeruleus, were allowed 40 min to attack single individuals of three species of butterfly: one relying solely on crypsis, the comma, Polygonia c-album; one relying on intimidating wing pattern in addition to crypsis, the peacock; and one intermediate species, the small tortoiseshell Aglais urticae. The results are in accordance with expectations and demonstrate that: (1) birds take longer to discover the leaf mimicking species, the comma, than the tortoiseshell and the peacock; (2) the comma remained motionless throughout experimental trials but small tortoise- shells and peacocks flicked their wings when attacked; (3) the most intimidating butterfly, the peacock, started flicking its wings at a greater distance from the attacking bird than the small tortoiseshell; and (4) the intimidating pattern and behaviour of peacocks was effective—when discovered, all peacocks survived interactions with blue tits, whereas only 22% of commas and 8% of small tortoiseshells survived. Introduction Predation exerts strong selective pressures on preys to evolve morphological and behavioural adaptations to decrease the risk of being detected, attacked, captured and consumed (Edmunds 1974). Examples of morphological anti-preda- tory adaptations range from cryptic coloration, decreasing the risk of being detected, to sharp fangs and spines, struc- tures used for retaliation and defence (Edmunds 1974; Ruxton et al. 2004). Behavioural adaptations in prey in- clude, for example, choosing a matching background to escape detection (Endler 1984) and displaying impressive weapons or armour to discourage an attacking predator (Edmunds 1974). Butterflies generally suffer from a substantial predation pressure which has selected for effective anti-predation defence, especially in long-lived species such as those that live for several months and hibernate as adult butterflies (e.g., Wiklund et al. 2003; Wiklund and Tullberg 2004). For an edible butterfly the best option for prolonged survival is to remain undetected. This is usually achieved when the coloration and the outline of the insect blend so well with the natural background that the attention of the predator is never alerted. Another way to escape predator attention involves specific resemblance (sensu Cott 1940) when a predator mistakes an insect for an inedible object such as a leaf. Specific resemblance is regarded as mimicry by some researchers (but not by others—Endler 1981; Rothschild 1981; Pasteaur 1982), but can be distinguished from general resemblance (Wiklund and Tullberg 2004). The latter aims to decrease detection risk, whereas the for- mer aims to decrease recognition risk, giving a prey the appearance of an inedible object, thereby making specific resemblance coloration functionally similar to mimicry in the strict sense. A second line of defence involves animal defensive action as soon as the predator has discovered the butterfly and is just about to seize it. Peacock butterflies (Inachis io), small tortoiseshells (Aglais urtica) and comma butterflies (Polygonia c-album) all hibernate as adults and exhibit leaf mimicry when resting (Brakefield et al. 1992). Recently, Wiklund and Communicated by M. Elgar A. Vallin (*) . S. Jakobsson . C. Wiklund Department of Zoology, Stockholm University, 106 91 Stockholm, Sweden e-mail: adrian.vallin@zoologi.su.se J. Lind School of Biology, University of St. Andrews, St. Andrews, Fife, Scotland, UK