Induction of Orange Head Coloration and Activation of Courtship and Aggression by Testosterone in the Male Broad-Headed Skink (Eumeces laticeps)

Abstract

Male Eumeces laticeps develop bright orange head coloration during the spring breeding season, when they fight with other males and engage in sexual behavior with females. Outside the breeding season the head color fades and the sexual and agonistic behaviors cease. Intraperitoneal implantation of testosterone propionate in Silastic capsules restores the bright orange head coloration and activates court- ship and agonistic behaviors in castrated males. As in many vertebrates, sexually dimor- phic behaviors and chromatic signals are known in a few lizards to be regulated by gonadal steroids. Male secondary sexual coloration develops following androgen treatments in the iguanid Sceloporus occi- dentalis (Kimball and Erpino, 1971) and in the scincid Eumeces fasciatus (Edgren, 1959). Among female lizards, bright secondary sexual coloration important in social com- munication (Cooper, 1984) develops in cer- tain species of Iguanidae in response to exogenous progesterone or testosterone treatments (Cooper and Ferguson, 1972a,