Interactions between behavior and plasma steroids within the scramble mating system of the promiscuous green turtle, Chelonia mydas

We measured plasma androgen (combined testosterone and 5 alpha-dihydrotesto sterone) (A) and corticosterone (B) in the promiscuous green turtle (Chelon ia mydas) during courtship in the southern Great Barrier Reef. This study e xamined if reproductive behaviors and intermale aggression induced behavior al androgen and adrenocortical responses in reproductively active male and female green turtles. Associations between reproductive behavior and plasma steroids were investigated in green turtles across the population and with in individuals. Levels across a range of both asocial and social behaviors were compared including (a) free swimming behavior; (b) initial courtship i nteractions; (c) mounted behavior (male and female turtles involved in copu latory activities); (d) intermale aggression (rival males that physically c ompeted with another male turtle or mounted males recipient to these aggres sive interactions); and (e) extensive courtship damage (male turtles that h ad accumulated excessive courtship damage from rival males). Behavioral and rogen responses were detected in male turtles, in that plasma A was observe d to increase with both attendant and mounted behavior. Male turtles who ha d been subjected to intermale aggression or who had accumulated severe cour tship damage exhibited significantly lower plasma A than their respective c ontrols. No pronounced adrenocortical response was observed after either in termale aggression or accumulation of extensive courtship damage. Female tu rtles exhibited a significant increase in plasma B during swimming versus m ounted behavior, but no change in plasma A. We discuss our results in terms of how scramble polygamy might influence behavioral androgen interactions differently from more typical combative and territorial forms Of male polyg amy. (C) 1999 Academic Press.