Love is in the air: additional evidence for a volatile sex-attractant pheromone in snakes

Many taxa utilise chemosensation as their primary sensory modality and communicate with one another using pheromones. Sex-attractant pheromones facilitate mate location and provide information regarding the reproductive status of the potential mate. Snakes have adaptively radiated to many different habitats, some of which preclude the possibility of depositing a continuous terrestrial pheromone trail (e.g., arboreal, semi-aquatic). We suggest that volatile signals are present in species inhabiting such environments. The majority of investigations into snake sex-attractant pheromones have examined terrestrial species, largely ignoring non-terrestrial species and their signal modality. We examined the potential existence of terrestrial and volatile signals in the northern watersnake (Nerodia sipedon) with a modified Y-maze. During the mating period, males of this semi-aquatic species successfully trailed both the terrestrial and volatile signals from estrous females but did not successfully trail the terrestrial or volatile signals from non-estrous females and other males. Whether a single multimodal sex-attractant pheromone (or multiple sex-attractant pheromones) produced this result remains unknown. However, we feel future investigations into the volatile nature of sex-attractant pheromones in the Ophidia would prove fruitful; particularly for arboreal, aquatic, and semi-aquatic taxa providing a greater understanding of communication and mating system dynamics.