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The chimpanzee populations of the Bossou and Nimba regions in West Africa were genetically surveyed to 1) reveal the genetic relationship between the Bossou and Nimba populations, and 2) elucidate the evolutionary relationship between the Bossou-Nimba and other West African populations. The chimpanzee group at Bossou is characterized by its small population size, no evidence of contact with neighboring populations, and no female immigration. It is believed that most females and adolescent males emigrate from this population. To reveal the genetic signature of these characteristics, we examined the genetic diversity of Bossou and two neighboring populations (Seringbara and Yealé) in the Nimba Mountains by sequencing approximately 605 bp of the mitochondrial DNA (mtDNA) control region. A total of 20 distinct mtDNA variants were observed from 56 sequences of noninvasively collected, anonymous samples. Nucleotide diversity in the Nimba Mountain populations was 0.03-0.04, and did not differ significantly from that in the Bossou population. Very few mitochondrial variants are shared among the sites sampled, which suggests that there is little gene flow involving mtDNA. Nevertheless, no clear population structures were revealed in either population. A comparison with published sequences from West African chimpanzees (Pan troglodytes verus) indicates that the variants observed in the Bossou and Nimba regions are scattered throughout the subspecies, rather than clustered according to geographic region. This suggests that the Bossou-Nimba populations derived only recently from the common ancestral population of the West African chimpanzees, and did not pass through a bottleneck.

We present a preliminary report on the differences and similarities in material culture among four neighbouring chimpanzee (Pan troglodytes verus) communities. One of these communities includes Bossou, a long-term field site of wild chimpanzees, in Guinea, West Africa. We also conducted surveys of three new sites. Two of those surveyed areas, Seringbara in Guinea and Yealé in Côte d'Ivoire, are located less than 12 km away from Bossou in the Nimba Mountains region, which forms a natural boundary between Guinea and Côte d'Ivoire. The third, Diécké, is situated further south-west, closer to the border with Liberia. During the surveys, we gathered behavioural information about these neighbouring populations of chimpanzees. The differences, as well as similarities, in material culture were tabulated based on our findings. The three behavioural variants found so far involve differences in nut cracking behaviour with regard to the species of nut cracked. Some variation in materials used for nut cracking has also been recorded. However, we still need to establish whether these local variations can be explained by the demands of the physical and biotic environments in which the populations of chimpanzees live. If these alternative hypotheses can be excluded with continuing research at the study sites, these differences are likely to be cultural behaviours that are influenced by the social context and mode, i.e. horizontal, vertical or oblique, of transmission, by the social structure and organisation of each community and/or perhaps by some form of social norms prevalent within these communities., (Copyright 2001 S. Karger AG, Basel)