Male Social Relationships
Principal investigators: Martin Muller, Kimberly Duffy, Ian Gilby, and Richard Wrangham

Male-male social bonds form the core of chimpanzee communities and are necessary for cooperative defense of the community, yet males compete intensely amongst themselves for social status and access to mates. Our research on male social relationships has focused on how male chimpanzee social behavior balances these conflicting needs and how relationships among particular males are formed and maintained. Recent research questions include: What are the contexts for aggression among male chimpanzees? How stable are male social relationships over time? How can alliances enhance the success of males in mating contexts? Is dominance rank correlated with hormonal function (i.e., testosterone) in males? What are the costs and benefits of high social rank in males?

Highlighted publications:

Duffy, KG, RW Wrangham, and JB Silk. 2007. Male chimpanzees exchange political support for mating opportunities. Current Biology 17: 586-587.
Muller, MN. 2002. Agonistic relations among Kanyawara chimpanzees. In: C Boesch, G Hohmann, and L Marchant (Eds.), Behavioral Diversity in Chimpanzees and Bonobos. Cambridge: Cambridge University Press, pp. 112-124.
Muller, MN and RW Wrangham. 2004. Testosterone, dominance and aggression in wild chimpanzees: a test of the challenge hypothesis. Animal Behaviour 67: 113-123.

Female social relationships
Principal investigators: Sonya Kahlenberg, Melissa Emery Thompson, Ian Gilby, Emily Otali, Kyleb Wild, Richard Wrangham

Unlike male chimpanzees, females are not very gregarious and both affiliative and agonistic interactions among females are rare. Thus, it has been difficult to understand the extent to which females form differentiated relationships and the function of these relationships. At Kanyawara, we have been able to use long-term data to better understand female social preferences and to contribute to new models for female competition. Our results highlight the costs and benefits of social interaction for females and the role of resource distribution on female competition and reproductive success. Females form stable dominance relationships and affiliative relationships based largely on location of their core areas within the habitat and selectively use aggressive behavior, including coalitions with other females, do defend access to these core areas.

Highlighted publications:

Emery Thompson, M, SM Kahlenberg, IC Gilby, and RW Wrangham. 2007. Core area quality is associated with variance in reproductive success in chimpanzees at Kanyawara, Kibale National Park. Animal Behaviour 73: 501-512.

Kahlenberg, SM, M Emery Thompson, and RW Wrangham. 2008. Female competition over core areas among Kanyawara chimpanzees, Kibale National Park, Uganda. International Journal of Primatology 29: 1497-1509.

Otali, E and JS Gilchrist. 2006. Why chimpanzee (Pan troglodytes schweinfurthii) mothers are less gregarious than nonmothers and males: the infant safety hypothesis. Behavioral Ecology and Sociobiology 59: 561-570.

Behavioral Endocrinology
Principal investigators: Martin Muller, Melissa Emery Thompson, Richard Wrangham

Many of our behavioral observations of chimpanzees can be enhanced by understanding underlying physiological processes. For instance, studies of adult male chimpanzees at Kanyawara have revealed correlations between dominance status, aggression, and testosterone levels, providing some of the first primate evidence for testosterone's role in mediating mating competition. These studies also indicate that males suffer physiological costs, measurable in glucocorticoid levels, of dominance behaviors. Our studies have led to insights about impact of dietary quality on female fecundity and, in turn, the impact of variable female fecundity on the intensity of male mating interest. We have also examined the stress responses of females to aggression received from males in sexually-coercive contexts and from other females in competition for foraging areas. The Kibale Chimpanzee Project has maintained daily non-invasive urine collections for the past 10 years and is applying these to longitudinal studies of energetics, stress and reproductive function over the life course.

Highlighted publications:

Muller, MN and RW Wrangham. 2004. Dominance, cortisol and stress in wild chimpanzees (Pan troglodytes schweinfurthii). Behavioral Ecology and Sociobiology 55: 332-340.
Emery Thompson, M. 2005. Reproductive endocrinology of wild female chimpanzees (Pan troglodytes schweinfurthii): methodological considerations and the role of hormones in sex and conception. American Journal of Primatology 67: 137-158.
Emery Thompson, M and RW Wrangham. 2008. Diet and reproductive function in wild female chimpanzees (Pan troglodytes schweinfurthii) at Kibale National Park, Uganda. American Journal of Physical Anthropology 135: 171-181.

Energetics and Feeding Ecology
Principal investigators: Nancy Lou Conklin-Brittain, Colin Chapman, Melissa Emery Thompson, Alexander Georgiev, Alain Houle, Sonya Kahlenberg, Richard Malenky, Martin Muller, Amy Pokempner, Herman Pontzer, Richard Wrangham

Chimpanzees are large-bodied apes with significant caloric needs for survival and successful reproduction. They rely on high quality fruits which are unevenly distributed in both time and space and compete for these resouces both within and between groups. KCP's research plan has been driven by understanding how energetic demands drive the daily lives of chimpanzees, from ranging and foraging strategies, to social behavior and reproduction. These studies include extensive research on the nutritional biochemistry of chimpanzee foods, locomotor budgets, and sex- and rank-related variation in resource access and social constraints. Our researchers have also been instrumental in developing and applying methods for quantifying food density and energetic status.

Highlighted publications:

Conklin-Brittain, NL, RW Wrangham, and KD Hunt. 1998. Dietary response of chimpanzees and cercopithecines to seasonal variation in fruit abundance: II. Nutrients. International Journal of Primatology 19: 971-987.
Pontzer, H and RW Wrangham. 2004. Climbing and the daily energy cost of locomotion in wild chimpanzees: implications for hominoid locomotor evolution. Journal of Human Evolution 46: 315-333.
Wrangham, RW, CA Chapman, AP Clark, and G Isabirye-Basuta. 1996. Social ecology of Kanyawara chimpanzees: implications for understanding the costs of great ape groups. In: WC McGrew, LF Marchant and T Nishida (Eds.) Great Ape Societies. Cambridge: Cambridge University Press: pp. 45-57.

Cooperation and Inter-Group Conflict
Principal investigators: Richard Wrangham, Ian Gilby, Martin Muller, Michael Wilson

Within communities, chimpanzee males form strong bonds that are thought to facilitate their cooperation in various contexts, particularly defense of the community feeding territory against neighboring groups. In Kanyawara and other chimpanzee communities, severe and sometimes deadly aggression occurs in both opportunistic encounters and deliberate raids of neighboring communities. Research by KCP scientists has elucidated important patterns from this violence, leading to greater understanding of this severe form of territoriality and its effects on the daily lives of chimpanzees. We are also examining male cooperation in the context of hunting for vertebrate prey. What factors influence participation in these costly behaviors, and what benefits do individual chimpanzees reap?

Highlighted publications:

Wrangham RW and D Peterson. 1996. Demonic Males: Apes and the Origins of Human Violence. Boston: Houghton Mifflin.
Wilson, ML, MD Hauser, and RW Wrangham. 2001. Does participation in intergroup conflict depend on numerical assessment, range location, or rank for wild chimpanzees? Animal Behaviour 61: 1203-1216.
• Gilby, IC, LE Eberly, and RW Wrangham. 2008. Economic profitability of social predation among wild chimpanzees: individual variation promotes cooperation. Animal Behaviour 75: 351-360.

Life History and Development
Principal investigators: Melissa Emery Thompson, Angela Garbin, Martin Muller, Emily Otali, Rebecca Stumpf, Richard Wrangham

Our long-term dataset at Kanyawara provides an excellent opportunity to study the life course of chimpanzees, which are particularly notable for their long lifespan (>50 years) and very slow rate of maturation and reproduction. Our researchers have been instrumental in producing important studies of mortality and fertility patterns over the chimpanzee lifetime. Such studies are critical foundations for understanding the evolution of human life histories, as well as highlighting key sources of variation in the reproductive success of individuals. In addition to demographic analyses, we are studying the effect of age on factors such as ranging patterns, social status, and reproductive function in both sexes. We are currently conducting multi-faceted examinations of the development of social behavior in chimpanzees.

Highlighted publications:

Hill, K, C Boesch, J Goodall, A Pusey, J Williams, and RW Wrangham. 2001. Mortality rates among wild chimpanzees. Journal of Human Evolution 40: 437-450.
Emery Thompson, M, JH Jones, AE Pusey, S Brewer-Marsden, J Goodall, D Marsden, T Matsuzawa, T Nishida, V Reynolds, Y Sugiyama, and RW Wrangham (2007). Aging and fertility patterns in wild chimpanzees provide insights into the evolution of menopause. Current Biology 17: 2150-2156.
Muller, MN, M Emery Thompson, and RW Wrangham. 2006. Male chimpanzees prefer mating with old females. Current Biology 16: 2234-2238.

Communication & Cognition
Principal investigators: Adam Clark-Arcadi, Sonya Kahlenberg, Andrew Whiten, Michael Wilson, Richard Wrangham

Among the more remarkable aspects of chimpanzee behavior is the manufacture and use of tools and the cultural transmission of tool use and other behaviors. In collaboration with researchers from chimpanzee research sites across Africa, KCP scientists have documented the distribution of such "chimpanzee cultures". Chimpanzees at Kanyawara, for instance, have been observed to use twigs as probes to extract liquids from tree crevices, as well as to chew leaves into effective sponges for absorbing water. Other culturally-transmitted and variable behaviors are less utilitarian, such as stripping leaves off of a twig as a signal from an interested male to a sexually attractive females, or carrying and nesting with a small branch as if it were a "doll". KCP researchers have also examined the form, function, and population variation in chimpanzee communication and the ability of chimpanzees to make tactical decisions based on probabilities of success.

Highlighted publications:

Whiten, A, J Goodall, WC McGrew, T Nishida, V Reynolds, Y Sugiyama, CEG Tutin, RW Wrangham, and C Boesch. 1999. Chimpanzee cultures. Nature 399: 682-685.
Arcadi, AC. 1996. Phrase structure of wild chimpanzee pant hoots: patterns of production and interpopulation variability. American Journal of Primatology 39: 159-178.
Wilson, ML, NF Britton, and NR Franks. 2002. Chimpanzees and the mathematics of battle. Proceedings of the Royal Society B: Biological Sciences 269: 1107-1112.