The Ecology and Behavior of New Chimpanzee Mothers at Ngogo, Kibale National Park, Uganda
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The ecology and behavior of new chimpanzee mothers at Ngogo, Kibale National Park, Uganda by Bethany Kaye Hansen A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Anthropology) in the University of Michigan 2016 Doctoral Committee: Professor John C. Mitani, Chair Associate Professor Jacinta C. Beehner Associate Professor Andrew J. Marshall Professor David P. Watts, Yale University DEDICATION To the chimpanzees of Ngogo, especially the females ii ACKNOWLEDGEMENTS This dissertation would not have been possible without the help and support of several individuals and organizations. I thank… John Mitani for his expert guidance and mentorship, especially in the areas of critical thinking and scientific writing. I am honored to have had the opportunity to work with such a proficient and dedicated primatologist. David Watts, whose knowledge of primates, as well as his work ethic, are truly inspiring. Jacinta Beehner, who provided invaluable training during the writing process and who always knew when a few words of motivation were needed. Andy Marshall, who broadened my view of statistics and urged me to try new techniques. And Beverly Strassmann, Barb Smuts, Abby Bigham, and Laura MacLatchy, who all contributed to my understanding of evolution and biological anthropology. I thank the late Jerry Lwanga, who not only provided logistical support at the Ngogo field site, but also shared much information about the forest, as well Ugandan culture. Tumusiime Alfred, Ndagizi Lawrence, Mbabazi Godfrey, and Twineomujuni Ambrozio assisted with data collection and provided training in the field. Alfred and ‘Ambrose’ went above and beyond their duties as field assistants, providing support for fundraising efforts for the Kyakagunga Community School. They also opened their homes to me, allowing me to spend time with their families. Tibisimwa James used his knowledge of the forest to lead anti-poaching efforts, along with his dedicated assistants. Businge Charles performed cooking and cleaning duties in camp, allowing me to spend so many hours observing chimpanzees. While in the field, Kevin iii Langergraber, Carolyn Rowney, Michelle Brown, and Bryce Carlson provided much-needed companionship. I also thank the Uganda Wildlife Authority, the Uganda National Council for Science and Technology, and the Makerere University Biological Field Station for permission to work in Uganda’s beautiful Kibale National Park. I thank the many scientists whose research on the Ngogo chimpanzees provided invaluable background and context for this dissertation, particularly: Sylvia Amsler, Kevin Langergraber, Brent Pav, Kevin Potts, Lauren Sarringhaus, Marissa Sobolewski, and Monica Wakefield. Biological anthropology students at the University of Michigan provided support and mentorship, especially Marcela Benitez, Elizabeth Johnson, Aaron Sandel, and Rachna Reddy. The Center for Statistical Consulting and Research at the University of Michigan provided invaluable assistance with data analysis. This dissertation would not have been possible without financial support from several organizations at the University of Michigan: the College of Literature, Science, and the Arts; the Department of Anthropology, the International Institute; Rackham Graduate School; the African Studies Center; and the Department of Afroamerican and African Studies. The University Committee on Use and Care of Animals at the University of Michigan approved my research program. Lastly, I extend the deepest and most heartfelt thanks to Kara C. Hansen and Ashley Lemke. Thank you for your friendship, wise words, and for always telling me, “You can do this.” iv TABLE OF CONTENTS Dedication…………………………………………………………………………………………ii Acknowledgements……………………………..……………………………………………......iii List of Figures…………………………………………………………………………….....…....vi List of Tables…………………………………………………………………………….…....…vii Abstract……………………………………………….…………………………………...……...ix Chapter 1. Introduction………………………………………………………………………………..1 a. Female chimpanzee socioecology and life history b. Female chimpanzee parity c. The Ngogo study site d. Goals of this dissertation e. References 2. Ranging behavior of female chimpanzees at Ngogo, Kibale National Park, Uganda...…16 a. Introduction b. Methods c. Results d. Discussion e. References 3. Aggression between wild female chimpanzees varies with parity………………………58 a. Introduction b. Methods c. Results d. Discussion e. References 4. Primiparous and multiparous female chimpanzees differ in patterns of intrasexual affiliation…………………………………………………………………………………88 a. Introduction b. Methods c. Results d. Discussion e. References 5. Conclusion……………………………………………………………………...………124 a. Female ranging patterns b. Female intrasexual aggression c. Female affiliative relationships d. Future directions e. References v LIST OF FIGURES 2.1 Minimum convex polygon estimating space use of female chimpanzee subjects………..….31 2.2 Minimum convex polygons estimating space use of individual female chimpanzees.….…..32 . 2.3 Dendrogram of the results of the UPGMA cluster analysis calculated from dyadic indices of ranging similarity for female study subjects……………………………………………….……34 2.4 Space use of female subjects separated by neighborhood……………………………..……35 3.1 Rates of aggression directed by chimpanzee mothers toward females in three reproductive categories………………………………………………………………………………………..72 3.2 Individual rates of aggression directed by primiparas and multiparas to females of varying reproductive status………………………………………………………………………….……74 4.1 Frequency of pairwise affinity indices of female chimpanzee association during three years of study…………………………………………………………………………………………101 4.2. Dendrogram of the results of the UPGMA cluster analysis calculated from the pairwise affinity indices for females in 2010…………………………………………………….………102 4.3. Dendrogram of the results of the UPGMA cluster analysis calculated from the pairwise affinity indices for females in 2011………………………………………………………….…103 4.4. Dendrogram of the results of the UPGMA cluster analysis calculated from the pairwise affinity indices for females in 2012…………………………………………………….………104 4.5. Pairwise affinity indices between parous female chimpanzees and female associates during three years of study……………………………………………………………………………..105 vi LIST OF TABLES 2.1. Summary of predictor variables for models predicting home range size (GLM1)………….27 2.2. Summary of predictor variables for models predicting home range size (GLM2)…...……..29 2.3. Comparison of attributes of two spatial neighborhoods of female chimpanzees…………...36 2.4. Major plant food species found in grid cells used most heavily by female chimpanzee subjects at Ngogo………………………………………………………………………………...37 2.5. Results of AICc analysis for three models of home range size in female chimpanzees…….38 2.6. Model-averaged coefficient estimates (including 95% confidence intervals) for averaged models……………………………………………………………………………………………38 2.7. Results of AICc analysis for 22 models of home range size in parous female chimpanzees.39 2.8. Model-averaged coefficient estimates (including 95% confidence intervals) for averaged models……………………………………………………………………………………………40 3.1 Schematic of potential interactions between two types of chimpanzee mothers and three types of female recipients………………………………………………………..……………………..67 3.2 Rates of aggressive interactions between female chimpanzees in three East African communities…………………………………………………………………………………...…70 3.3 Rates of decided aggressive interactions between female chimpanzees in the Ngogo community…………………………………………………………………………………...…..70 3.4 Individual rates of intrasexual aggression directed by chimpanzee mothers in two East African communities………………………………….……………………………………….…71 3.5 Results of GLM1, a test of the effect of recipient parity on the rate of intrasexual aggression directed by chimpanzee mothers……………………….………….……………………………..73 3.6 Results of GLM2, a test of the effect of the interaction of aggressor and recipient parity (AR) on the rate of intrasexual aggression directed by chimpanzee mothers…….……………………75 vii 3.7 Demographic characteristics of the Ngogo chimpanzee community during two studies……77 4.2 Results of GLM2, a test of the effect of the interaction of parity of associates on the duration of intrasexual grooming involving chimpanzee mothers……………………………………….108 4.3 Results of GLM4, a test of the effect of the interaction of groomer and recipient parity on the rates of intrasexual grooming received by chimpanzee mothers……………………………….110 viii ABSTRACT Female mammals invest heavily in reproduction, and theory and empirical research indicate that two factors influence their fitness. First, females require food to reproduce and mothers should compete for access to food resources. Second, recent research indicates that in group- living species, females who form strong social bonds with each other reproduce more than do females who are unable to forge similar relationships. Therefore, females must meet both nutritional and social needs in order to reproduce successfully. Understanding the complex relationship between reproduction and socioecology promises to shed light on how evolution shapes the behavior of mothers. Although mothers face a common set of challenges involving competition and affiliation, evidence indicates that within species, not all mothers are the same. One factor, parity, affects females in diverse taxa, including primates, carnivorans, and cetaceans. Due to their inexperience, primiparas, mothers raising their first offspring,