Effects of experimentally elevated testosterone on plasma glucocorticoids, body mass, and recapture rates in yellow-pine chipmunks, Tamias amoenus.
In male yellow-pine chipmunks plasma levels of glucocorticoids (GCs) are low while plasma testosterone (T) levels peak during the mating season, suggesting that T suppresses GC levels. To test this hypothesis, free-living, post-reproductive males were implanted during summer with either a T-filled (T-males) or an empty silastic implant (controls or C-males). Body mass and plasma levels of corticosterone, cortisol, and T were measured immediately before and 1 month after implantation. Exogenous testosterone increased T to high physiological levels typical of reproductively active males. By 1 month after implantation, T-males decreased their mean body mass and plasma GC levels, while C-males maintained their mean body mass and GC levels. Even though T-males lost mass, recapture success 1 month after implantation for T-males (71%) was equal to that of C-males (71%). However, the overwinter recapture rate of C-males (83%) was significantly greater than that of T-males (20%). The results support the hypothesis that high plasma T of males during mating has a suppressive effect on plasma GC levels. Additionally, experimentally elevated T significantly reduced the rate of recapture during the following spring, and this may reflect a reduction in local overwinter survival. The suppression of adrenocortical activity by T may contribute to the reductions in prehibernation body mass and post-emergence recapture success. J. Exp. Zool. 287:378-383, 2000.
Place
N J
NJ
Department of Zoology, University of Washington, Seattle, Washington 98195-1800, USA. ned@socrates.berkeley.edu
D000222:Adaptation, Physiological; D000818:Animals; D015992:Body Mass Index; D005938:Glucocorticoids / Q000032:analysis*; D008297:Male; D012098:Reproduction; D012589:Sciuridae / Q000502:physiology*; D012621:Seasons; D013739:Testosterone / Q000032:analysis / Q000494:pharmacology*
D005938:Glucocorticoids; D013739:Testosterone