Population size and structure of the Ngogo chimpanzee community in the Kibale Forest, Uganda, and the impact of tourism
Although both species of chimpanzees, the common chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus) show a so-called fission-fusion social organisation, they differ significantly in the details of social relationships between and within genders. These differences have been linked to ecological differences between the species, habitats. Common chimpanzees living in forested habitats were put forward as providing a link between common chimpanzees in less forested habitats and bonobos. In this study, the Ngogo community of Kibale Forest in Uganda was investigated to determine whether it is justified to say that forest-living chimpanzees exhibit characteristics in their social organisation which resemble both the common chimpanzees in less forested habitats and the bonobos. From January 1992 to June 1993, focal animal samples on adult males, anoestrous and oestrous females yielded data on party size and composition, social interactions and time budgets. Statistical analysis suggested that the Ngogo chimpanzees resemble common chimpanzees from other habitats in party size and composition, intra- and intersexual relationships more than bonobos, whereas their time budget resembles more that of bonobos. A comparison with data from the literature suggests that intraspecific variation of social organisation may be as great as interspecific variation. In the second part of the study, the impact of habituation and tourism on the Kanyancu community of chimpanzees in the Kibale Forest was monitored. From February 1992 to June 1993, chimpanzees' initial reactions to contacts with human observers were recorded together with other factors such as numbers of observers present and the method used to locate the chimpanzees. On 54 occasions with various numbers of observers (and/or tourists) present, activity rates were recorded for the observed individuals. Numbers of observers present (up to 5) had no impact on the chimpanzees, initial reaction, and the only significant change in activity caused by higher numbers of observers (up to 15) was an increasing vocalisation rate. As visitor satisfaction declines with groups of more than six to eight people it is suggested that tourist groups viewing chimpanzees should be kept at a maximum number of 10 (including guides).