Ecological Factors Influencing Bonobo Density and Distribution in the Salonga National Park: Applications for Population Assessment

Bonobos (Pan paniscus) and mountain gorillas (Gorilla beringei) are Africa’s two most endangered great apes (Butynski 2001). Conservation action plans for bonobos (Thompson-Handler et al. 1995, Coxe et al. 2000) emphasize the need for regional surveys in order to determine species distribution and abundance, to identify priority populations for protection, and to develop a range-wide conservation strategy (Susman 1995, Wolfheim 1983). Little is known about environmental factors limiting bonobo population distribution within their range. The distribution is thought to be patchy and discontinuous even in areas where seemingly suitable forests exist (Horn 1980, Kano 1984, Malenky et al. 1989, Thompson-Handler et al. 1995). Salonga National Park (SNP), the first and largest federally protected area for the bonobo, is a priority survey site. Created in 1970 as a reserve for bonobos and forest elephants (Loxodonta africana cyclotis), the SNP covers ca. 36,000 km2, potentially harboring the largest area of undisturbed and legally protected bonobo habitat (D’Huart 1988, Thompson-Handler et al. 1995). In Salonga, several bonobo distribution hot-spots have been discovered by large-scale and site-based surveys (Blake 2005, Reinartz et al. 2006). Some authors consider them to be discrete populations (Inogwabini and Ilambu 2005). However, apart from natural barriers to dispersal, e.g., rivers, it is unknown whether true boundaries exist between proposed populations and what ecological parameters may determine their limits.