1Anthropology, University of Michigan, 2Reproductive Endocrinology, Smithsonian Institution
Thursday 2:00-2:15, Ballroom B
Territoriality and hunting are energetically and psychologically demanding aspects of male chimpanzee behavior that have significant reproductive consequences. The discrete nature of territorial and hunting competitions permitted us to investigate anticipatory urinary hormone secretion associated with these behaviors in the Ngogo chimpanzee community, in Kibale National Park, Uganda.
The stress response allows an individual to quickly alter its physiological and behavioral profile in response to acute changes in its social and physical environment. Here, we investigated the correlation between cortisol, a stress hormone, territorial and hunting aggression. Our results indicate that hunting and territoriality are facilitated by increases in adrenal activity and cortisol production in wild chimpanzees, as cortisol levels are high during and shortly after engaging in these behaviors. Additionally, these data showed that cortisol does increase before any aggression transpires. Our earlier results indicate that male chimpanzees also display anticipatory increases in testosterone in advance of territorial behavior but not hunting. This suggests that chimpanzees are physiologically differentiating between these events. The potential cues chimpanzees use to anticipate these behaviors are unknown. Therefore, we investigated two correlates of hunting and territorial behavior, large male party size and location in territory, which could be potentially responsible for these anticipatory increases. However, neither could explain the anticipatory increases in cortisol. Being on the periphery of their territory was not associated with elevated cortisol levels, while cortisol levels were higher when males were in smaller groups. The potential cues that explain the observed anticipatory increases in cortisol are still unknown.
This research was supported by grants from the L.S.B. Leakey Foundation and the U.S. National Science Foundation (IOB-0516644; BCS-0752637).