Effects of estrogen and male head coloration on chemosensory investigation of female cloacal pheromones by male broad-headed skinks ( Eumeces laticeps)

Abstract

Indirect experimental evidence suggests that pheromone production and responsiveness to pheromones in a lizard, the broad-headed skink ( Eumeces laticeps), are regulated by sex steroid hormones. For study of estrogenic effects on female pheromone levels, tongue flicking by males was recorded in response to chemical samples from the female cloaca, the secretion site of the female sex pheromone. Cloacal chemicals from estrogen-treated females elicited higher tongue flick rates by all males than samples from sham-injected females. Male head coloration is bright orange in the breeding season, but fades to tan outside the breeding season. The availability of males having the full range of head coloration due to asynchronous onset of breeding condition in a laboratory population made it possible to examine the relationship between head coloration and responsiveness to female pheromones. Males with brightly colored heads, presumably reflecting higher underlying androgen levels, performed more tongue flicks in response to cloacal chemicals from estrogen-treated females than did males with tan heads. Male head coloration did not affect responsiveness to cloacal chemicals from sham-injected females.