Meeting Abstract
46.2 Jan. 6 Does Testosterone Mediate Parental Care in Female Dark-eyed Juncos? O’NEAL, D.M.*; REICHARD, D.G.; PAVLIS, K; KETTERSON, E.D.; Indiana University, Bloomington; Saint Mary’s College of Maryland; University of Guelph; Indiana University, Bloomington daoneal@indiana.edu
Hormonal manipulations allow us to create novel phenotypes in order to learn how existing phenotypes evolve and why they persist. In the male dark-eyed junco (Junco hyemalis), experimental elevation of testosterone (T) is known to decrease male parental care and offspring survival, but to result in higher overall fitness owing to higher mating success. To understand this surprising result and also to understand selective forces that influence variation in T in birds, we focused our attention on females. Previous studies in juncos demonstrated that elevated T in female juncos does not suppress female incubation behavior, suggesting that female parental behavior is insensitive to T. In this study we asked whether T might mediate parental care behaviors other than incubation. T levels in females were experimentally elevated to their spring maximum using subcutaneous implants. We videotaped free-living females at the nest and measured brooding behavior when the young were three days old and feeding behavior when the young were six days old. We also measured nest defense behavior by quantifying responses to a mounted predator placed near the nest. T-implanted females showed a significant reduction in the amount of time spent brooding when compared to controls. They did not differ from controls in the number of nestlings fed per hour or in overall provisioning rate. Interestingly, males mated to T-implanted females fed young significantly more than males mated to control females. With respect to nest defense, T-implanted females performed significantly more dives at the predator than control females but did not differ in other behaviors. We conclude that some aspects of female parental behavior are sensitive to T and others are not, and we consider the implications for the evolution of T-mediated characters in both sexes.
