Meeting Abstract

P3.139  Jan. 6  Aggression in female dark-eyed juncos (Junco hyemalis): a role for progesterone? JAWOR, Jodie*; KETTERSON, Ellen; Indiana University, Bloomington; Indiana University, Bloomington jodie.jawor@usm.edu

In female mammals, progesterone (P) can influence sexual receptivity, maternal, and intrasexual aggression. Less is known about the role of P in female birds. Previous studies in dark-eyed juncos (Junco hyemalis) found that when females establish dominance they do not elevate testosterone (T), raising the question of whether P might play a role in female aggression. In this study we asked whether resident females altered either P or P/T ratios in response to an intrusion by a female conspecific, and whether P co-varied with the type of aggression shown. Research was conducted during the breeding seasons 2005-2006 with females held captive in semi-natural conditions. Thirty-five females were allowed to associate with a male for 2 days prior to the introduction of either a conspecific intruder or a heterospecific control intruder. Plasma samples were collected from resident females prior to their introduction to the male and following 30min of interaction with intruders. During intrusions resident females were observed for the type and number of aggressive acts displayed. Plasma was analyzed for P and T using tritium-based RIA. Females increased P following an intrusion, but the magnitude of increase was not affected by intruder type. In the case of T, there was a near significant interaction between the magnitude of change in T and intruder type. There were no significant effects of intrusion or intruder on P/T ratios. Finally, levels of hormones were not related to the aggression shown. We conclude that P but not T increased regardless of intruder type and the increase may have been a response to associating with a male. The findings do not support a role for P in female intrasexual aggression in juncos. However, further studies are needed to determine whether P functions in relation with other hormones to influence aggression.