Effect of fall mating on ovarian development in the red-sided garter snake

Although spring mating is an important factor in initiating vitellogenesis in female red-sided garter snakes (Thamnophis sirtalis parietalis), some females can become vitellogenic without having mated in the spring. Two hypotheses have been proposed to explain this phenomenon: 1) long-term storage of copulatory stimuli from mating the previous fall, or 2) additional cue(s) overcoming the lack of mating to stimulate vitellogenesis. Through oviductal biopsy, the presence of sperm in females returning to the hibernaculum in the fall was assessed. Laparotomies performed just before and 6 wk after hibernation indicated that although fall mating may stimulate slight ovarian development in the fall, there appears to be no effect of fall mating on spring ovarian recrudescence. Spring mating seems to be the most important factor in determining ovarian maturation. Therefore, it appears that there is no long-term storage of copulatory cues and that other as yet unknown cues are responsible for initiating vitellogenesis in spring unmated females.