BEHAVIOURAL TRIANGULATION OF THE HEAD IN THREE BOIGINE SNAKES: POSSIBLE CASES OF MIMICRY

ABSTRACT

In Israel three rear-fanged snakes (Colubridae: Boiginae) of the genus Telescopus possess a defensive display in which they coil, pose in readiness to strike, and often simultaneously flatten and triangulate the head. Thus they become similar to the venomous Viperidae in general. On indirect evidence, two of them appear to be mimics of sympatric viperid species. The desertic T. dhara somewhat resembles Echis coloratus, and, in Africa, more closely, E. carinatus. The Mediterranean T. fallax vaguely resembles Vipera palaestinae in Israel but it more closely resembles V. ammodytes in Greece, V. xanthina in Anatolia and V. lebetina on Cyprus. The possible evolution of such mimetic systems, Batesian, Müllerian, Mertensian or combined, which presumably begins with the convergence of cryptic coloration, is discussed. The desertic, black-headed T. hoogstraali seems to lack any specific mimetic partner. This might be due to its recent derivation from T. fallax without loss of the behaviour, or more reasonably to some unknown predator that avoids viper-shaped snakes in general.