O’NEAL, D.M.*; PAVLIS, K.; KETTERSON, E.D.; Indiana University, Bloomington; University of Guelph; Indiana University, Bloomington: The Effects of Experimentally Elevated Testosterone on Parental Care in Female Dark-eyed Juncos

Experimental elevation of plasma testosterone (T) in male dark-eyed juncos (Junco hyemalis) has been shown to decrease male parental care, but results in an overall fitness increased due to increased mating success. Potential benefits associated with higher levels of T in males may, however, be offset by deleterious effects in females. In an earlier study we reported that T does not suppress female parental behavior when females are incubating. In this study, we asked whether T interferes with female parental care when females are caring for nestlings. In particular we asked whether T affects nestling feeding or nestling defense. T levels in females were experimentally elevated to their spring maximum using subcutaneous implants. We measured female behavior in the field when young were six days old by videotaping feeding behavior at the nest and by quantifying responses to a mounted predator placed near the nest. T-implanted females showed a significant reduction in the number of nestlings fed per hour and in overall provisioning rate as compared to controls. T- implanted females also exhibited less nest defense than control females, and their nests were more likely to be lost to predators. The reduction in parental behavior due to elevated T indicates that both sexes are sensitive to suppression of parental behavior by T. Our results also suggest that the negative fitness consequences from reduced female parental care may act to constrain the evolution of higher levels of T in male juncos.