Richard W. Wrangham

Feeding Competition and Patch Size in the Chimpanzee Species Pan Paniscus and Pan Troglodytes

The relative importance of feeding competition in Pan paniscus and Pan troglodytes schweinfurthii is examined in an attempt to understand the major differences in social organization of the two species. P. paniscus at Lomako is characterized by a stronger tendency for association among females than among female P. troglodytes at Gombe. Party size in P. paniscus is dependent on patch size. Feeding competition was more important in small patches than in large patches. The total amount of feeding time by a party in a patch (chimp-minutes) was a measure of patch size that was available for both chimpanzee species. P. paniscus was found to have larger party sizes and to use larger food patches than P. troglodytes. The importance of dispersed ground foods for each species of chimpanzee was compared and, although the results are not conclusive, they indicate that this type of food was equally important in the diets of both populations. Two hypotheses of the ecological basis for differences in social structure are compared in light of this evidence.

Local Differences in plant-feeding Habits of chimpanzees between the Mahale Mountains and Gombe National Park, Tanzania

Plant-feeding habits of chimpanzee populations ( Pan troglodytes schweinfurthii ) were compared between the Gombe National Park and Mahale Mountains, Tanzania. Comparison of food lists revealed 15 clear differences in the frequency of eating species which occur commonly in both areas. Feeding techniques also differed in at least three commonly eaten food types. Factors responsible for the local variation of the food items and feeding techniques are discussed.

Sexual coercion in primates and humans : an evolutionary perspective on male aggression against females

Introduction and Theory * Male Aggression and Sexual Coercion of Females in Primates Martin N. Muller, Sonya M. Kahlenberg and Richard W. Wrangham * Evolution of Sexual Coercion with Respect to Sexual Selection and Sexual Conflict Theory Jana J. Watson-Capps * Inter-Sexual Conflict in Primates: Infanticide, Paternity Allocation, and the Role of Coercion Parry Clarke, Gauri Pradhan and Carel van Schaik Sexual Coercion and Mate Guarding in Non-Human Primates * Orangutans: Sexual Coercion Without Sexual Violence Cheryl Knott * Male Aggression Against Females in Mountain Gorillas: Courtship or Coercion? Martha Robbins * The Causes and Consequences of Male Aggression Directed at Female Chacma Baboons Dawn M. Kitchen, Jacinta C. Beehner, Thore J. Bergman, Dorothy L. Cheney, Catherine Crockford, Anne L. Engh, Julia Fischer, Robert M. Seyfarth and Roman M. Wittig * Female-Directed Aggression and Social Control in Spider Monkeys Andres Link, Anthony Di Fiore and Stephanie N. Spehar * Male Aggression Against Females and Sexual Coercion in Chimpanzees Martin N. Muller, Sonya M. Kahlenberg and Richard W. Wrangham * Sexual Coercion in Dolphin Consortships: a Comparison with Chimpanzees Richard C. Connor and Nicole L. Vollmer * Male Aggression toward Females in Hamadryas Baboons: Conditioning, Coercion, and Control Larissa Swedell and Amy Schreier Sexual Coercion and Mate Guarding in Humans * Coercive Violence by Human Males Against Their Female Partners Margo Wilson and Martin Daly * The Political Significance of Gender Violence Lars Rodseth and Shannon Novak * Intimate Wounds: Cranio-Facial Trauma in Women and Female Chimpanzees Shannon Novak and Mallorie Hatch * Human Rape: Revising Evolutionary Perspectives Melissa Emery Thompson Female Counterstrategies *Friendship with Males: A Female Counterstrategy to Infanticide in Chacma Baboons of the Okavango Delta Ryne Palombit * The Absence of Sexual Coercion in Bonobos Tommaso Paoli * Sexual Coercion, Patriarchal Violence and Law Diane L. Rosenfeld Summary and Conclusions * Sexual Coercion in Humans and Other Primates: The Road Ahead Richard W. Wrangham and Martin N. Muller * List of Contributors * Index

Rates of predation on mammals by gombe chimpanzees, 1972–1975

Rates of chimpanzee predation on mammals are calculated using data on 75 kills recorded during focal observation in Gombe National Park, Tanzania, from January 1972 to April 1975. The chimpanzees were members of two study communities (Kanyawara, or Northern, and Kahama, or Southern, community), and were observed as focal individuals for 14,583 hr by more than 30 researchers and field assistants working in pairs. The rate of predation by females was too low to allow reasonable estimates. For males, the mean rate of killing during the study period was 0.31 kills per male per 100 hr (N=17 males), or 4.65 kills per 100 hr in the two communities. In contrast to results from Mahale Mountains, there was no difference in predation rate between wet and dry seasons. However, predation rates varied over time, increasing by four times between the first three and last four seasons of the sample period. In an average year the 15 adult and subadult male chimpanzees are calculated to have killed 204 prey per year in an area of 16 km2, varying between 99 and 420 prey per year in periods of low and high predation rate. Red colobus were the most frequent prey, followed by bushpig and bushbuck. Predation rates varied greatly on different prey species, and were not related to either the proportion of time spent within 200 m of male chimpanzees, or to their population densities. In relation to encounter rates and population density, baboons, blue monkeys, and redtail monkeys were killed at a fraction of the rate of red colobus monkeys, which suffered severe mortality from chimpanzee predation. Predation on bushpig and bushbuck also appears to have been high in relation to population density. The amount of food provided by predation is estimated to have averaged 600 kg per year for chimpanzees in the two communities (totalling 14–17 adult or subadult males, 18–20 adult of subadult females, and about 19 infants or juveniles). This suggests that adult males consumed around 25 kg of meat per year, although any average figure undoubtedly masks considerable individual variation. Present data suggest that chimpanzees in Gombe and Tai National Park, Ivory Coast, prey on mammals at rates higher than other populations.