Female sex pheromone in the skin and circulation of a garter snake.

Serums and extracts of tissues from the female garter snake (Thamnophis sirtalis parietalis) each act as a pheromone and elicit male courtship behavior when applied to the back of another male. Since pheromonal activity is present in yolk and liver tissue of untreated females and can be induced with estrogen treatment in the serums and livers of males, the pheromone may be associated with the circulating yolk lipoprotein, vitellogenin.