Behavioural cues were used to assay the capacity of common lizards to detect chemical deposits of snakes. The lizards were observed in cages that had been previously inhabited either by one of two species of snake that feed on lizards (the viper Vipera berus and the smooth snake Coronella austriaca), or the grass snake (Natrix natrix), which does not feed on lizards. As a control, the lizards were tested both in a clean cage and in one sprayed with a pungent odorant. The lizards responded to the snakes' chemicals by increased tongue-flick rates, with the highest rates being given in response to the deposits of their predators. The chemosensory examination of the snakes' odours induced a shift in general behaviour in response to the predator, but not to the non-predator chemical cues. This behavioural response consisted mainly of a disruption of the locomotor patterns. Our findings strongly suggest that lizards detected and distinguished between the chemicals deposited by three species of snake. Behavioural performances were highly variable among individual lizards in all trials, but the relative scores of individuals tended to be similar in response to different stimuli.
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