Cross-dressing in Chemical Cues: Exploring ‘She-maleness’ in Newly-emerged Male Garter Snakes

Abstract

She-males are male garter snakes that elicit courtship behavior from other males during the breeding season. Initially thought to consist of a small sub-set of males which retained their attractive nature throughout the breeding season, recent behavioral data suggests that most, if not all, males undergo a period of ‘she-maleness’ upon first emerging from winter hibernation before losing their attractive nature shortly after emergence. Utilizing behavioral experiments and chemical analyses, we sought to discern whether newly-emerged male red-sided garter snakes (Thamnophis sirtalis parietalis) display a pheromone profile similar to the female sexual attractiveness pheromone. Sequestered in the skin lipids of females and responsible for triggering male courtship behavior, this pheromone has been previously linked with long-term she-maleness in this species. Results from courtship trials demonstrated that newly-emerged males are attractive to other males, although not to the same degree as females. Subsequent chemical analyses of skin lipids from females and newly-emerged males showed no quantitative or qualitative difference in the components constituting the sexual attractiveness pheromone. Thus, it appears that the majority of males in this species emerge with a female-like pheromone profile and subsequent physiological changes, yet to be identified, are responsible for the short- vs. long-term nature of this phenomenon.