Meeting Abstract

53.2  Saturday, Jan. 5  Induction of female pheromone production in male garter snakes PARKER, M. Rockwell*; MASON, Robert T.; Oregon State Univ.; Oregon State Univ. parkermi@science.oregonstate.edu

Organisms that rely solely on chemical signals to determine the sex of conspecifics serve as good models for understanding the effect of hormonal manipulation on signal production. Red-sided garter snakes (Thamnophis sirtalis parietalis) emerge in the thousands every spring in the Interlake region of Manitoba, Canada, and large mating balls form as males compete for females. Females elicit courtship via the sexual attractiveness pheromone, but some males in the population (“she-males”) produce the female pheromone and can thus elicit courtship from other males in the den. I investigated the ability of steroid hormones to induce female pheromone production in male snakes. I created four groups (n=12 ea.) in the summer of 2006: SHAM, GX (no testes), E2 (17β-estradiol implant), and GXE2 (no testes + E2 implant). The snakes were artificially hibernated in the lab and then transported to the field for behavioral tests at the den in the spring of 2007. The E2 and GXE2 groups elicited more courtship from males than did the SHAM and GX groups in two types of mating trials: arena trials with 10 courting males and mating ball tests in the den. Further, trailing experiments with wild males from the den showed that trails produced by estrogen-treated males were indistinguishable from large female scent trails and preferred over trails left by small females, wild she-males, and SHAM males. These results suggest that pheromone production in she-males is directly regulated by estrogen, which implies that exogenous estrogen may have the potential to alter the sexual phenotype of other adult male vertebrates.