Richard Wrangham - US grants

This grant provides support for two years of field research by Dr. Wrangham and his colleagues in the Kibale Forest which is located in southern Uganda. This area has an extremely high density of primates and the reseachers will focus their attention on the common chimpanzee Pan troglodytes . In the two related aspects of the study they will study the process of chimpanzee group socialization and also examine the food calls made by these animals. To accomplish these goals, they will make focal observations on adults encountered within the study area. They will record both activities of individual animals and will also note the composition of the group of which this animal is a member. A series of such observations will allow the reconstruction of the composition, fission and fusion of such groups. The team will also conduct focal tree.watches on fruiting trees and this will allow them to study how different groups and individuals share valuable limited resources. They will record information on the ecology of the entire study area to determine both density and distribution of resources. Finally they will record chimpanzee vocalizations and through a combination of laboratory and situational analysis attempt to determine the number of different calls and the purpose or meaning of each. The goal of this study is to understand the factors which determine how chimpanzees utilize the environment and the relationship between this strategy and group composition. Previous research has made it clear that in different parts of Africa these animals are organized differently and it seems likely that environment plays a role. However no detailed studies have been conducted to answer this question. Closely related to the question of group organization is the issue of cooperation between individuals. Since vocalization sometimes serves to announce the presence of food, through a study of calls, insight will, hopefully, be gained into the kinds of cooperation which take place. This research is important for several reasons. First it sets the context for understanding how humans act. Secondly data collected may help to preserve these rare animals which are endangered in many parts of Africa. Finally, because of the participation of Ugandian students and scientists it should help strengthen the Ugandian scientific establishment and help forge links between Ugandian and U.S. reseachers.

A new hypothesis has been proposed for the function of conspicuous sexual traits in female primates. The conventional view has been that certain female traits that occur in sexual contexts, such as sexual skin swellings, are designed to attract the attention of or incite competition between males in multi-male species. However, this view does not explain why females in these species would need to advertise their reproductive state so conspicuously or why conspicuous traits would incite more competition among males than would otherwise occur. In contrast, Pagel argues that conspicuous sexual males because they advertise the female's quality or condition. The signals evolve in response to male mate choice and competition among females to attract males (the mirror image of what has been normally accepted). While the female competition hypothesis is the most developed hypothesis to date for the function of conspicuous sexual advertisement in female primates, no tests have been made of its predictions. This dissertation project will examine variation in female sexual traits and their influence on female attractiveness to males in wild olive baboons at Gombe national Park in Tanzania. No study to date has been designed to test the hypothesis that male sexual interest is influenced by variation in any of these female traits in the wild, although it has been apparent that males mate selectively. This study will make a substantial first step towards understanding the evolutionary and social significance of female sexual signals and sexual attractiveness, a topic clearly of vital importance for understanding human evolution. It will also result in the training of young experts in the area of social behavior.

Ecology and endocrinology of aggression in chimpanzees.
Richard Wrangham

This study will investigate how aggression among wild chimpanzees is related to age, sex, endocrine status and seasonal variation in energy availability. From 2004 to 2009 the research team will compile a daily record of chimpanzee behavior and ecology within the Kanyawara community of Kibale National Park. The Kanyawara community is a social group of 50 chimpanzees that Wrangham has monitored since 1988, and that are well habituated to the presence of humans. In addition to systematically recording a wide range of behaviors, the research team will also collect urine samples at a rate of about 100 per month. A total of about 11000 urine samples will be available from 1997 to 2009. The concentrations of testosterone, cortisol, progesterone and estradiol will be assayed in these samples.
The researchers will test hypotheses about the relationship of steroid production to behavior (e.g. intergroup aggression, hunting, or status competition), and to behavioral contexts (e.g. mating competition for attractive vs. less attractive females). To do so, they will create a relational database and data management system. This will permit investigations of questions about relatively long-term, infrequent, and complexly related processes in chimpanzee behavioral biology. Long-term questions include how male endocrine status changes with dominance rank, how the frequency of aggression changes with age, or how and why female core areas shift or remain stable over time. Questions about infrequent events include how testosterone output is related to mate-guarding, to border patrols, or to hunting. Complexly related processes include relationships among behavior, party composition, and location. In sum, this research will provide information on a wide range of chimpanzee behaviors, including reproductive strategies, life-histories and social relationships, and will seek to understand them in terms of local ecology and in comparison to other populations.

Chimpanzees will be observed in Kibale National Park, Uganda, to test the hypothesis that daily variation in urinary C-peptide (UCP) levels among adult males is correlated with both food intake and energetically expensive behaviors, such as aggression. The C-peptide molecule is a by-product of insulin synthesis and when excreted in the urine gives an accurate indication of insulin production. Insulin stimulates the uptake of glucose from the bloodstream and thus reflects the availability of energy for the organism.

This study will provide the first direct assessment of the effectiveness of C-peptide, as an index of energy balance in wild primates. Previous assessments have been indirect since they used monthly averages of dietary quality, rather than daily monitoring of individual behavior. This research is designed to explain why dominant male chimpanzees have been reported to have lower UCP levels than subordinates, even though UCP levels track energy intake, being higher when and where fruit availability is greater.

The intellectual merit of this study lies in the possible implications its findings will have for the methodological development of energetics research in field conditions. Non-invasive indices of the energetic condition of primates have always been elusive. C-peptide is promising as an indicator of energetic balance, energy intake, or energy expenditure and this study will assess its value. Understanding the relationship between energy expenditure in male chimpanzees and their dominance rank will also reveal hitherto overlooked energetic costs of dominance in social mammals.

The broader impacts of the project include the contribution to the functioning of Makerere University Biological Field Station. Educational programs will be carried out in local schools to raise awareness and interest in wildlife. This doctoral dissertation research project will contribute to the academic training of a graduate student and the results will be published in peer-reviewed journals.

All human societies regularly process their foods by thermal and non-thermal means. This feature distinguishes humans from other species, and may even be compulsory from an energetic perspective, given that we possess relatively small molars and gastrointestinal tracts that commit us to an easily digestible diet. Yet the energetic significance of food processing and its evolutionary implications have barely been considered. This study tests the hypothesis that thermal and non-thermal processing lower the metabolic cost of food digestion, known as diet-induced thermogenesis (DIT). Effects will be evaluated for tubers and meat, foods widely exploited by humans and believed to have been critical resources for ancestral hominins. In theory, processing of these foods should result in a loss of structural integrity that lowers DIT due to reduced chewing and gastric effort, as well as increased access by digestive acids and enzymes. Since heat should weaken food structural integrity to a greater extent by gelatinizing starch and collagen, it is further predicted that the effects of thermal processing will exceed those of non-thermal processing. To evaluate these predictions, energy expenditure data are collected via respirometry from subjects before and after standardized meals served raw and whole, raw and pounded, roasted and whole, or roasted and pounded, based on a counterbalanced within-subjects design. Rats will be used as model organisms in the interests of low cost and high control, but a subset of trials will be replicated using human subjects to validate the animal model.

This study will quantify the impacts of thermal and non-thermal processing on DIT, an important factor in energy balance. Results will improve our understanding of the energetic returns of food processing and inform models of hominin transitions toward higher dietary quality. Low DIT has been implicated as a factor in the development of obesity. By determining the effects of food processing on DIT, this research contributes basic data that could help consumers influence the partitioning of meal energy to metabolism versus body stores. Results will thus be communicated broadly to peer-reviewed journals and conferences in anthropology and nutrition, as well as public forums. This doctoral dissertation research project will also contribute to the professional development of a female graduate student.

Of central importance in the science of human biology, as well as that of other species, is full understanding of the complex processes that underlie development, including both the integration of these processes and their evolutionary bases. While experiences during the critical period of childhood are known to have important and lasting effects on future growth, reproduction, health and behavior, the fundamental biology of this system remains poorly understood. This is especially salient for the human species, which has the longest juvenile phase of any animal. By incorporating a phylogenetic approach that examines physical, hormonal, and behavioral development in our closest living relative, the chimpanzee, we can advance understanding of this critical period of development, and determine how different developmental trajectories interact with each other and with the environment to produce adult traits. Comparison of chimpanzees and humans will provide a model for the ways in which biological influences combine with the ecological and social environments to generate adult characteristics, and contribute to understanding when and how unique features of human life history arose in our lineage (such as early weaning, prolonged reliance on parental support, and the adolescent growth spurt).

By using a series of novel, non-invasive techniques, this study will achieve the first detailed documentation of the development of wild chimpanzees, and provide the basis for a comparative, phylogenetic approach to the science of primate, including human, development. Trajectories to be analyzed include physical growth (linear growth, body weight, muscle mass, and tooth eruption), nutrition (behavioral measures of nursing intensity, hormonal measures of maternal and infant energy balance, and isotopic measures of maternal and infant diet), hormones (testosterone, cortisol, estradiol, progesterone, DHEAS and C-peptide), and multiple dimensions of behavior. Hypotheses to be tested will assess how maternal condition, early life nutrition, stress, and related factors influence the timing and rates of development, and the role of hormones in these interactions. The results will be important for understanding sex differences in physiology and behavior. Ultimately, understanding these relationships will allow us to better infer life history shifts associated with changing habitats, ecologies, and morphologies in the hominin evolutionary lineage.

Numerous domestic and international broader impacts are tied to the project. Data generated by the research will be utilized to promote K-12 education in the U.S., working with teachers in both New York and New Mexico to enhance curricula and foster science literacy and appreciation. Education and training of both U.S. and Ugandan undergraduate and graduate students will be fostered through incorporation of these students into the project, and through utilization of the generated data for future research. International collaboration and capacity building, as well as conservation of endangered species, will be promoted by providing economic incentives for protection in Kibale National Park (job creation, training, research fees), supporting anti-poaching and ecotourism programs, and educating Ugandan primary school children about wildlife and habitat conservation.