Chemical cues from both dangerous and nondangerous snakes elicit antipredator behaviours from a nocturnal lizard

Abstract

Many prey species use chemical cues to detect predators. According to the threat sensitivity hypothesis, prey should match the intensity of their antipredator behaviour to the degree of threat posed by the predator. Several species of lizards display antipredator behaviours in the presence of snake chemical cues, but how species specific are these responses? In Australia, most snake species eat lizards, and are therefore potentially dangerous. Hence, we predicted that lizards should display generalized rather than species-specific antipredator behaviours. To test this prediction, we quantified the behavioural responses of velvet geckos, Oedura lesueurii, to chemical cues from five species of elapid snakes that are syntopic with velvet geckos but differ in their degree of danger. These five snake species included two nocturnal ambush foragers that eat geckos (broad-headed snake Hoplocephalus bungaroides, and death adder, Acanthophis antarcticus), two active foragers that eat skinks (but rarely eat geckos) and that differ in their activity times (nocturnal small-eyed snake, Cryptophis nigrescens, and diurnal whip snake, Demansia psammophis), and a nocturnal nonthreatening species that feeds entirely on blind snakes (bandy-bandy, Vermicella annulata). Geckos showed similar antisnake behaviours (tail waving, tail vibration), and a similar intensity of responses (reducing activity, freezing), to chemical cues from all five snake species, even though the snakes differed in their degree of danger and foraging modes. Our results suggest that velvet geckos display generalized antipredator responses to chemicals from elapid snakes, rather than responding in a graded fashion depending upon the degree of threat posed by a particular snake species.