Meeting Abstract

P3.143  Jan. 6  Behavioral consequences of elevated testosterone in female dark-eyed juncos (Junco hyemalis) REICHARD, D.G.*; O’NEAL, D.M.; KETTERSON, E.D.; Saint Mary’s College of Maryland; Indiana University; Indiana University dgreichard@smcm.edu

Through experimental elevation of plasma testosterone (T), novel phenotypes can be created and tested for relative fecundity and viability and thus for likelihood of being favored by natural selection. Previous studies have shown that elevated T in male dark-eyed juncos (Junco hyemalis) results in greater fitness due to increased mating success, despite reductions in parental care. The constraint hypothesis predicts that this fitness gain might be offset by deleterious effects of elevated T in females, which may explain why high T males have not evolved. In the female dark-eyed junco, previous studies have suggested that females are behaviorally insensitive to T during the incubation stage, which argues against the constraint hypothesis. In this study I asked whether experimentally elevated T affects maternal aggression towards conspecifics during incubation or nestling brooding behaviors in an effort to determine potential fitness consequences associated with elevated T. Incubating females implanted with T-filled or empty implants were presented with a conspecific male at the nest, and attack intensity was measured for fifteen minutes. Brooding behavior of females and male provisioning were observed for four hours when nestlings were three days old. Increased T had no effect on maternal aggression, providing additional support for female insensitivity to T during incubation. Conversely, high T females spent less time on the nest and spent less time brooding than control females, suggesting that aspects of female parental behavior are sensitive to T during the nestling stage. Further study will show whether these aspects might prove detrimental and conceivably constrain the evolution of T in females or males.