Foreword : conserving great apes / Jane Goodall -- Toward an understanding of the orangutan's social system / Carel P. van Schaik and Jan A.R.A.M. van Hooff -- Comparative socio-ecology of gorillas / David P. Watts -- Comparative socio-ecology of Pan paniscus / Frances J. White -- Social ecology of Kanyawara chimpanzees : implications for understanding the costs of great ape groups / Richard W. Wrangham ... [et al.] -- Ranging and social structure of lowland gorillas in the Lopé Reserve, Gabon / Caroline E.G. Tutin -- Sympatric chimpanzees and gorillas in the Ndoki Forest, Congo / Suehisa Kuroda ... [et al.] -- Dietary and ranging overlap in sympatric gorillas and chimpanzees in Kahuzi-Biega National Park, Zaïre / Juichi Yamagiwa ... [et al.] -- Social grouping in Taï chimpanzees / Christophe Boesch -- Coalition strategies among adult male chimpanzees of the Mahale Mountains, Tanzania / Toshisada Nishida and Kazuhiko Hosaka -- Male rank order and copulation rate in a unit-group of bonobos at Wamba, Zaïre / Takayoshi Kano -- Comparing copulations of chimpanzees and bonobos : do females exhibit proceptivity or receptivity? / Yukio Takahata, Hiroshi Ihobe and Gen'ichi Idani -- Conflict as negotiation / Frans B.M. de Waal -- Language perceived : paniscus branches out / E. Sue Savage-Rumbaugh ... [et al.] -- Reciprocation in apes : from complex cognition to self-structuring / Charlotte K. Hemelrijk -- Chimpanzee intelligence in nature and in captivity : isomorphism of symbol use and tool use / Tetsuro Matsuzawa -- Comparative positional behavior of the African apes / Diane M. Doran -- Nest building behavior in the great apes : the great leap forward? / Barbara Fruth and Gottfried Hohmann -- Comparative studies of African ape vocal behavior / John C. Mitani -- On which side of the apes? Ethological study of laterality of hand use / William C. McGrew and Linda F. Marchant -- Savanna chimpanzees, referential models and the last common ancestor / Jim Moore -- Reconstructions reconsidered : chimpanzee models and human evolution / Adrienne Zihlman -- Afterword : a new milestone in great ape research / Junichiro Itani