Individual variation in testosterone and parental care in a female songbird; The dark-eyed junco (Junco hyemalis) |
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Authors: | Kristal E. Cain Ellen D. Ketterson |
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Affiliation: | 1. Research School of Biology, The Australian National University, ACT 0200, Australia;2. Department of Biology, Indiana University, Bloomington, IN 47405, USA;3. Center for the Integrative Study of Animal Behavior, Bloomington, IN 47405, USA |
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Abstract: | When competition for sex-specific resources overlaps in time with offspring production and care, trade-offs can occur. Steroid hormones, particularly testosterone (T), play a crucial role in mediating such trade-offs in males, often increasing competitive behaviors while decreasing paternal behavior. Recent research has shown that females also face such trade-offs; however, we know little about the role of T in mediating female phenotypes in general, and the role of T in mediating trade-offs in females in particular. Here we examine the relationship between individual variation in maternal effort and endogenous T in the dark-eyed junco, a common songbird. Specifically, we measure circulating T before and after a physiological challenge (injection of gonadotropin releasing hormone, GnRH), and determine whether either measure is related to provisioning, brooding, or the amount of T sequestered in egg yolk. We found that females producing more T in response to a challenge spent less time brooding nestlings, but provisioned nestlings more frequently, and deposited more T in their eggs. These findings suggest that, while T is likely important in mediating maternal phenotypes and female life history tradeoffs, the direction of the relationships between T and phenotype may differ from what is generally observed in males, and that high levels of endogenous T are not necessarily as costly as previous work might suggest. |
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Keywords: | Life history tradeoffs Endogenous steroids Testosterone Gonadotropin releasing hormone (GnRH) Maternal care Yolk hormones Dark-eyed junco (Junco hyemalis) |
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