Plasma corticosterone response to an acute stressor varies according to reproductive condition in female tree lizards (Urosaurus ornatus).

The magnitude of the glucocorticoid response to a stressor can depend on both environmental and physiological context. One factor that has not been examined is whether females of different reproductive states have different responses to a stressor. We examined whether corticosterone (CORT) increased after a 10 min handling stress in oviparous female tree lizards (Urosaurus ornatus) that were vitellogenic (yolking follicles) or gravid (post-ovulatory). We found that stressed vitellogenic females had a large increase in plasma CORT whereas gravid females did not. Baseline levels of CORT in gravid females were relatively high and similar to those in stressed vitellogenic females. The lack of a stress response in gravid females may be due to an inability to secrete higher levels of CORT or a suppression of the stress response. In addition, within vitellogenic females, CORT was positively correlated with ovarian weight, suggesting that CORT may function in some aspect of ovarian development during vitellogenesis.