Individual variation in testosterone and parental care in a female songbird; the dark-eyed junco (Junco hyemalis).
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.
Research School of Biology, The Australian National University, ACT 0200, Australia; Department of Biology, Indiana University, Bloomington, IN 47405, USA; Center for the Integrative Study of Animal Behavior, Bloomington, IN 47405, USA. Electronic address: kristalcain@gmail.com.
Kristal E
KE
Cain
Ellen D
ED
Ketterson
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D004530:Egg Yolk / Q000737:chemistry / Q000378:metabolism; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007206:Individuality; D008297:Male; D008425:Maternal Behavior / Q000187:drug effects / Q000502:physiology*; D009425:Nesting Behavior / Q000187:drug effects / Q000502:physiology; D020308:Songbirds / Q000502:physiology*; D013739:Testosterone / Q000032:analysis / Q000097:blood*
D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone
Dark-eyed junco (Junco hyemalis); Endogenous steroids; Gonadotropin releasing hormone (GnRH); Life history tradeoffs; Maternal care; Testosterone; Yolk hormones