Ranging Patterns of Chimpanzees in a Montane Forest of Kahuzi, Democratic Republic of Congo

I studied ranging patterns of a semihabituated unit-group of chimpanzees for 60 mo at Kahuzi. They had a total home range of 12.81 km2 and a mean annual home range of 7.55 km2. Considering the low density of chimpanzees in the area vis-à-vis chimpanzees in arid areas, their home range is very small. Kahuzi chimpanzees used the home range in a clumped pattern, frequently visiting the core area and only rarely entering peripheral areas. The monthly range changes with fruit availability, increasing during periods of fruit scarcity. There was no consistent seasonal difference in the size of the home range. However, use of different habitat types may vary seasonally. While there was no seasonal effect in the use of primary forest, the chimpanzees showed a statistically consistent seasonal difference in their use of secondary forest, visiting it mainly during the dry season when fig trees were in fruit. Since the primary forest provides them with more food fruits, chimpanzees tended to use more frequently the small patches of primary forest in their home range. Thus, the size and distribution of small fragmented primary forests may be an important factor influencing the ranging pattern of chimpanzees at Kahuzi.