Behavioral effects of long-chained ketones in Vipera ammodytes: an experimental approach

Snakes heavily depend on chemical communication and use chemical cues for trailing, foraging, searching for mates, and other behaviors. Snake pheromones reported so far are complex mixtures, consisting mainly of heavy, long-chained ketones. However, such ketones cannot be detected in the sex pheromones of some species, and for others, airborne compounds are suggested to participate in intersexual communication. Thus, to establish whether a certain compound is part of the snake sex pheromone, behavioral assays should be performed. The most frequently found ketones in the skin extracts of Vipera ammodytes (Linnaeus, 1758) are 2-pentacosanone and 2-heptacosanone, which are hypothesized to participate in intraspecific communication. In the present study, we test male and female individuals’ responses to paper towels soaked with these two ketones (separately and together), n-hexane, heptacosane, and a control. We suggest that the ketones produced by V. ammodytes have a role in intraspecific communication and demonstrate that they elicit specific courtship-related behaviors in males, but not in females. Our results further show that 2-pentacosanone and 2-heptacosanone evoke sexual attraction, with their combination proving more effective than either compound alone, although the modest response suggests that other compounds may also be involved. We suggest that there are additional compounds, of a different nature, that most likely constitute the female sex pheromone. We hypothesize that males can also produce these ketones, which may provide them with a mating advantage by emitting false cues to rivals.