Behavioral and physiological responses to experimentally elevated testosterone in female dark-eyed juncos (Junco hyemalis carolinensis)

Devin A. Zysling, Timothy J. Greives, Creagh W. Breuner, Joseph M. Casto, Gregory E. Demas, Ellen D. Ketterson

    Research output: Contribution to journalArticlepeer-review


    Testosterone mediates the expression of many fitness-related traits in male vertebrates and is thought to account for numerous sex differences in trait expression. Testosterone is also secreted by females; however, far less is known regarding its effects on female physiology and behavior. Using a bird species in which the effects of testosterone on males are well characterized, the dark-eyed junco (Junco hyemalis), we tested whether an increase in exogenous testosterone in females would alter the phenotypic expression of a suite of behavioral and physiological traits. We found that increased testosterone levels in female dark-eyed juncos led to decreased cell-mediated immune function and increased intrasexual aggression, hypothalamo-pituitary-adrenal (HPA) axis responsiveness, baseline corticosterone and corticosterone-binding globulin (CBG) levels. Furthermore, immunosuppression following testosterone implantation was negatively correlated with total and free testosterone but did not appear to be related to either total or free corticosterone. These results demonstrate that the phenotypic impact of elevated testosterone is not confined to males in dark-eyed juncos, and that the impact in adults can be similar in males and females. We discuss these results in the context of potential endocrine-immune interactions and the evolution of sexual dimorphism.

    Original languageEnglish
    Pages (from-to)200-207
    Number of pages8
    JournalHormones and Behavior
    Issue number2
    StatePublished - Aug 2006


    • Corticosterone
    • Corticosterone-binding globulin
    • Endocrine-immune interaction
    • Hormonal correlation
    • Immune
    • Phytohemagglutinin A
    • Sexual dimorphism
    • Steroid hormone
    • Testosterone


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