Evidence for a female sex pheromone mediating male trailing behavior in the red-sided garter snake, Thamnophis sirtalis parietalis

Male garter snakes locate females during the breeding season utilizing cons pecific trailing behavior. It has been hypothesized that the female-derived chemical cue responsible for mediating male reproductive trailing behavior is the sexual attractiveness pheromone, a previously characterized contact pheromone responsible for releasing male courtship behavior. To examine th is hypothesis, we tested the response of male red-sided garter snakes, Tham nophis sirtalis parietalis, to pheromone trails produced by males, females and 'she-males'. She-males are a small subset of males in the natural popul ation that are morphologically and behaviorally similar to other males exce pt that they produce and express the sexual attractiveness pheromone during the breeding season. When tested on a Y-maze, males were found to detect a nd follow the skin lipid trails of females and she-males, but displayed no behavioral responses to male trails. In addition, males were unable to disc riminate between she-male and female trails when given a choice. These resu lts are consistent with the hypothesis that the sexual attractiveness phero mone is the chemical cue primarily utilized by males to mediate reproductiv e trailing behavior.