My primary research interest lies in the interacting biological and behavioral strategies of males and females in primate social systems. My current research focuses on hamadryas baboons (Papio hamadryas hamadryas), which have been characterized as the most male-dominated primate species, one in which social organization is largely if not exclusively controlled by males. Such a social system lies at the far extreme of known variation in sex roles among primates, and begs explanation. As a means to elucidate the role of female behavior in hamadryas social organization, I have focused my research over the past 12 years on the behavior and ecology of wild hamadryas baboons in Ethiopia.

Hamadryas baboon social organization centers on one-male units (OMUs), or 'harems', in which a single 'leader male' maintains exclusive sexual access to a small group of females. The cohesive force maintaining the OMU structure is the behavior of the leader males, who condition females to remain nearby by threatening them and biting them on the nape of the neck (Swedell & Schreier in press). Previous accounts of hamadryas baboon behavior had suggested that females were unable to even have, let alone pursue, their own social and reproductive strategies. My own research, beginning with my dissertation research in 1996-1998 and continuing to the present, suggests that hamadryas females do in fact pursue their own social and sexual agenda. For example, females appear to develop and maintain social relationships with other females (Swedell 2002); females may be able to influence the outcome of male takeovers of one-male units (Swedell 2000, 2006); and female reproductive behavior may include strategies specifically oriented towards preventing infanticide by males (Swedell and Tesfaye 2003; Swedell and Saunders 2006).

My current research focuses on further exploration of the interaction of biology and behavior in hamadryas and other baboons. For example, having found that social relationships among hamadryas females appear to be more important than previously thought, I would like to ascertain whether these social relationships are influenced by biological kinship. In addition, further characterization of both male and female strategies in the hamadryas social system hinges on a determination of the leader male's share of paternity of the infants born into his one-male unit. Hamadryas leader males make strenuous efforts to maintain exclusive access to the females in their one-male units, but females do copulate with other males surreptitiously. We do not yet know, however, how often these surreptitious copulations lead to conception. Finally, it has been long thought that the hamadryas social system is fundamentally different from that of other baboons in its reversed pattern of male philopatry and female dispersal. This notion, however, has yet to be confirmed with any conclusive detail. My current goals, therefore, are to obtain a combination of behavioral and genetic data from as many individuals in our study group as possible in order to address the above questions. The answers to these questions will tell us more about hamadryas baboon behavior and should have implications for both male and female reproductive strategies in other baboons and primates as a whole.

In collaboration with Julian Saunders and Mathew Pines, I am currently directing most of my research efforts towards a study focusing on the role of follower males in hamadryas social organization. Within the unusual multi-tiered social system of hamadryas baboons, OMUs coalesce into larger groupings called clans and bands. Present in clans and bands but not associated with individual OMUs are solitary males, who move throughout the band and interact with other solitary males and juveniles. Some OMUs also include one or more follower males, who consistently associate with a particular OMU. Within this system, it seems fairly certain that most males eventually gain females and become leaders; however, it is not clear why, on the path to that role, some males become solitary and others become followers. It is also unclear why leader males tolerate followers in their OMUs. Whether leaders and followers are close relatives is not known, though it has been speculated that they are half siblings and that they both benefit from this relationship via inclusive fitness. Using a combination of behavioral, genetic, and hormonal data, we are comparing the social and sexual strategies of follower males with those of solitary males in order to (1) document the life history trajectory of males before, during, and after they are follower males, (2) characterize the leader-follower relationship, (3) determine the explanatory paradigm behind the dichotomy between solitary and follower males and the relative costs and benefits of each, and (4) assess why leader males tolerate the presence of follower males in their OMUs.

As a complement to my work on hamadryas baboons, I am also expanding my research to include chacma baboons of the Cape Peninsula of South Africa. There, I am collaborating with South African colleagues and students to investigate the impact of social structure, social behavior, and human disturbance on stress, reproduction, and sexual strategies in chacma baboons. Ultimately, I would like to make direct comparisons between chacmas and hamadryas in order to shed light on the evolution of social and reproductive strategies in Papio baboons as a whole.

In addition to projects on which I have taken the lead role, I am also supervising several projects led by my graduate students. My first student, Amy Schreier, focused her research on the relationship between resource distribution, social structure, and ranging patterns of hamadryas baboons at Filoha. Amy defended her dissertation in September 2008 and will receive her Ph.D. from CUNY in 2009. Shahrina Chowdhury, a current CUNY student, is conducting her dissertation fieldwork on the relationship between social bonds, stress, and reproduction in female hamadryas baboons at Filoha. Kumara Wakjira, an M.Sc. student at Moi University in Kenya, is conducting research on the behavioral ecology of the Bale monkey in Bale Mountains National Park in Ethiopia. In the Cape Peninsula of South Africa, Jacqui Stephenson, a B.Sc. honours student at the University of Cape Town, recently completed a project on behavioral indicators of stress in female chacma baboons (Stephenson et al., 2008), and Angela van Doorn (Ph.D. candidate, University of Cape Town) is currently writing up her dissertation on the relationship between management practices and the behavioral ecology of chacma baboons in southern latitudes.

For more information on my current research and collaborators, please see the Filoha Hamadryas Project website and the Cape Peninsula Baboon Research Unit website.