This book comes from a conference on ‘Behavioural Diversity in Chimpanzees and Bonobos’, held 11–17 June, 2000 at the monastery of Seeon in southern Bavaria, Germany. Organized by Gottfried Hohmann and Christophe Boesch, and monitored by Linda F. Marchant, the cloistered meeting heard reports from 30 researchers on 13 different populations of these African apes. Instead of publishing proceedings of the conference, we decided to organize a collection of integrated findings on key topics. Thus, the chapters in this book deviate from the contributions to the Seeon conference in several ways. First, most chapters were greatly edited in order to draw direct comparisons across sites and between species. Second, for the same purpose, some authors who gave separate presentations at the meeting agreed to prepare combined chapters. Third, to enlarge the scope of the book, we asked others who were not present at the meeting to contribute.

This book is the result, and it is devoted only to research on wild populations of Pan, a hominoid genus with two sister species, chimpanzee (P. troglodytes) and bonobo (P. paniscus). Although many research facilities offer excellent housing and stimulating social and non-social environments, when compared with field data, the steady flow of resources, reduced fluctuation in health, safety from predators, and constrained movements limit the ecological validity of their findings.

Behavioural diversity is not a new research topic. There is a rich tradition in comparative ethology of examining given behaviours across species (Lorenz 1950; Hinde & Tinbergen 1958; Wickler 1967; Eibl-Eibesfeldt 1975). These studies focused on species-typical behavioural patterns by comparing closely related taxa.