S12-4 Thu Jan 7 11:00 – 11:15 Glucocorticoids correlate with and predict social status in the cooperatively breeding lance-tailed manakin (Chiroxiphia lanceolata) Jones, BC*; DuVal, EH; Bennington College; Florida State University firstname.lastname@example.org http://blakecarltonjones.com
Cooperation is a feature of many social species and occurs when one organism increases the potential fitness of another at an apparent cost to their own. Many have saught to explain the ultimate mechanisms of the evolution of cooperative behaviors, but less is known about the proximate mechanisms that drive cooperation. We assessed the potential link between stress physiology and social behavior in a tropical bird that displays variation in social status, which plays a key role in cooperative courtship. Many lance-tailed manakin males form partnerships to perform complex displays for potential mats. These partnerships are dominated by an alpha male, while subordinate beta males help to attract females but rarely have the opportunity to breed. While most males participate in cooperative displays, many individuals do not cooperate as an alpha or beta, termed ‘marginal males’. Glucocorticoids, steroid hormones associated with the physiological stress response, often correlate with behavioral phenotypes and have been associated with dominant and subordinate behaviors in other species. We found that stress-induced and baseline levels of glucocorticoids differed among alphas, betas, and marginal males. Further, stress-induced concentrations of glucocorticoids predicted future social trajectories. Juvenile males with high stress-induced measures of glucocorticoids were more likely to attain beta or alpha status within the first 2 years of becoming a reproductively mature male. These finding suggest that glucocorticoids play an important role in social status and the formation of male-male alliances. Higher levels of baseline and stress-induced glucocorticoids may reflect the energy demands associated with courting females. However, the predictive nature of stress-induced glucocorticoids suggests the link reflects more than immediate metabolic demands.