Plasma corticosterone and testosterone levels during the annual reproductive cycle of male brown anoles (Anolis sagrei).

The objective of the present study was to determine the plasma levels of testosterone and corticosterone in male Anolis sagrei during the annual reproductive cycle and to examine the relationships between seasonal change in the levels of these hormones, male reproductive activity, and body condition. Both testosterone and corticosterone levels in adult males captured in the Miami, Florida, area varied significantly with month and with season (i.e., breeding vs. nonbreeding period), although they were not significantly correlated with each other or with body mass. Mean monthly testosterone levels were higher during the breeding season (March-August) than during the nonbreeding season, with the one exception that the highest mean testosterone level occurred in February immediately before the beginning of the breeding season. Testosterone levels in the overall sample of 144 males were significantly correlated with testes mass but not with any of the other measured variables. Corticosterone levels were highest during the nonbreeding season and lowest during the breeding season. Corticosterone levels on a monthly basis were negatively correlated with monthly changes in testes mass and positively correlated with monthly changes in abdominal fat-body mass.