Intellectual Merit: This three-year project focuses on inter-group dynamics of agressive behavior. Referred to as aggressive inter-group encounters (IGEs), face-to-face confrontations between groups typically involve the participation of one or a few group members, which means that the costs of aggressive competition are borne by only a few participants. Although this pattern is widespread, it remains unclear which social, ecological, and physiological factors cause some individuals to participate in an IGEs, but not others. Previous studies focused on factors like dominance rank, food and mate availability, and the degree of relatedness to group-mates. This research includes assessments of these traditional factors but also includes the contribution of previously unexamined variables - temperament and energetic balance. Both variables are likely to be meaningful predictors of participation in inter-group encounters and will affect the understanding of collective aggression in a wide range of taxa. This research studies four groups of vervet monkeys at the Mawana game reserve in KwaZulu-Natal, South Africa, with laboratory analysis conducted at the University of New Mexico, USA, and data analysis and write-up conducted at the University of Zurich.
Broader Impacts: The topic of inter-group aggression and insights gained from this project will be of great relevance to behavioral ecologists, anthropologists, and psychologists. Project results will be disseminated through peer-reviewed publications, conference presentations, and public media in South Africa, Switzerland, and the United States.
In addition, the Fellow intends to mentor a minority undergraduate student and hire as an intern based on his or her level of interest in animal behavior at the University of New Mexico. The Fellow will also create and maintain a blog about data collection in South Africa and laboratory analysis at UNM. With collaboration with Peter Rouget Middle School in Brooklyn, NY (most of students are minority, first-generation immigrants students from household of low socio-economic status), the blog will introduce to the students observational behavioral research, field work in the natural environment, primate socioecology, and conservation through the Fellow's personal narrative, photos, videos, and a question-and-answer section.
Intellectual Merit Activities In this postdoctoral research project, I sought to answer two fundamental questions about individual participation in collective aggression – i.e., conflicts that arise between social groups. First, why does an individual participate in some fights, but not others? Second, why do some individuals participate more consistently than others? The results of this study yielded several exciting and novel findings. As I had hypothesized, I found that both temperament and energy balance are better predictors of whether an individual will participate in collective aggression than the traditional factors, such as dominance rank and reproductive status. I found that there are two behavioral types among redtail monkeys: ‘cheaters’ and ‘cooperators.’ Whereas cooperators sometimes participate during aggressive intergroup encounters (IGEs), cheaters never do so. Both behavioral types exhibit low energy balance (indicated by levels of urinary C-peptide of insulin) in weeks without IGEs. However, during weeks with IGEs, they differ dramatically: cheaters still exhibit low energy levels, but cooperators have very high energy levels – regardless of whether they actually participated in the IGEs. Intriguingly, this difference in energy balance is not a result of differential access to contested food resources – both cheaters and cooperators had the same access to food trees. It appears that cheaters face a persistent, long-term energetic barrier to participation that cannot be rectified through short-term access to a feeding site. I will use the data that I collected during this project to determine whether cheaters and cooperators differ in other social contexts, such as grooming, within-group aggression, and cooperative responses to predators. In the coming years, I hope to extend this study to determine whether an individual’s energy profile can change over longer time periods, and if such changes mirror differences in aggressive participation in collective action. I also examined fecal cortisol, a steroid hormone that varies in response to psychological and energetic stressors and which correlates with some aspects of temperament. By controlling for urinary C-peptide levels as an indicator of energy stress, I isolated the variations in cortisol that were due to psychological stress. Overall, cheaters experienced greater social stress than cooperators, but cooperator’s stress levels were highest when they participated aggressively in IGEs. Thus, the conditions that elicit active participation in an IGE are high energy balance and social stress levels. As a result of this work, I can answer a long-standing question about the differences in collective behavior between humans and other animals. A collective action problem exists when a few individuals participate and bear the costs of doing so, yet most or all of the social group reaps the benefits of the collective action. If cooperators suffer the costs and experience reduced benefits, why do they tolerate cheaters? In redtails, it is now clear that no true collective action problem exists, and that it is inaccurate to label non-participants as ‘cheaters’ – they face a much greater energetic hurdle than cooperators, and the energetic benefits of collective action are insufficient to close the energetic gap. In humans, it is assumed that cheaters and cooperators face equivalent energetic costs and benefits; further research is needed to test this assumption. Broadening Participation Activities As a minority, I am particularly well-positioned to act as a mentor to other students from under-represented groups. I brought one such student to Uganda, who had recently completed her undergraduate studies at Long Island University. This student spent six months in Kibale National Park in which I taught her how to conduct field work and helped her execute a comparative study at the Ngogo and Kanyawara field sites. She is now preparing to enter a veterinary medicine program with an eye toward future research in wildlife epidemiology and zoonotic diseases. I have also been mentoring a Ugandan college graduate for the last two years, who now plans to enter a master’s program in wildlife studies in the near future. While in the US, I have given presentations about my work at my high school alma mater (which has a substantial minority population), four universities (Florida Atlantic University; University of New Mexico; University of California, Santa Barbara; and Kent State University); and two conferences (American Association of Physical Anthropologists and the Animal Behavior Society). I plan to continue my mentoring and presentation activities for the next several years as I work toward disseminating my research findings. This postdoctoral research project has been a key step for my own career in academia; as a result of my work, I was short-listed for two tenure-track jobs in my first year on the market and received two lectureship and one tenure-track offer.
