Sex at the snake den: lust, deception, and conflict in the mating system of red-sided gartersnakes

Studying the behavior of snakes is a difficult logistical challenge in most cases, but a few populations make it easy. Most notably, many thousands of red-sided gartersnakes (Thamnophis sirtalis parietalis) emerge from communal dens in Manitoba in early spring and court and mate before dispersing to their summer ranges. We have exploited that opportunity to conduct detailed investigations of gartersnake behavior. Our observations and field experiments reveal intense sexual conflict, sophisticated chemical communication systems, and a flexible adjustment of reproductive tactics to local biotic and abiotic conditions. For example, newly emerged male snakes produce female-like pheromones and thereby attract courtship from other males, thereby warming the she-male and accelerating his recovery from overwintering. With a few flicks of his tongue, a mate-searching male can identify another snake's species, sex, body length, body condition, and mating history. The distinctive courting behaviors of male snakes impede female respiration, inducing an antipredator response (cloacal gaping) that allows forcible insemination. Females use facultative tactics to avoid harassing males. Our research on a snake population that (almost uniquely) allows direct observations and experiments has revealed a suite of complex and flexible behaviors that snakes use to enhance their individual reproductive success.