The Sudden Decline of a Community of Chimpanzees at Gombe National Park: A Supplement

Since writing my former article (PAN 7-1) at the start of March 2000, more evidence has come to light as to the means by which the southern community may have fallen in numbers. During May 2000 villagers informed researchers, that chimpanzee had been observed up to 3 km south of the Park's southern boundary. Subsequent investigations revealed two areas outside the Park's boundary, which were being regularly utilised at this time by the chimpanzees.
Running from the Park's southern boundary, on the west side of the Rift Escarpment are two gullies. One runs down to the lakeside village of Kazinga, and the other runs down to the lakeside village of Ngelwe. Both villages are sections of the larger village of Mtanga, 2-3 km south. Whereas Kazinga is home to a relatively high proportion of Congolese, Ngelwe neighbouring it one valley south is home to a relatively high number of Burundians. At the base of each gully, villagers keep crops of bananas, palm nuts, and mangoes. The upper slopes remain relatively undisturbed by farming activity. However such is the demand on land for cultivating purposes that within as little as one to two years all remaining woodland will have been cleared. Certainly farming activity and the clearing of trees has begun on the upper slopes of Ngelwe gully.
The chimpanzees have been observed by villagers in this area on a regular basis during April- May and September- October each year. Investigations of Ngelwe gully at the end of May revealed a relatively high number of beds between a few weeks and two months in age. During May one female was observed to feed on Strychnos innocua on Ngelwe gully's cultivated lower slopes. This is one of the few tree species, which farmers tend not to clear immediately since the wood is not a desirable source of charcoal.
During May one male chimpanzee was observed to feed on palm nuts at the base of Ngelwe gully, literally in the village of Ngelwe itself. The chimpanzees' presence in this area during September-October coincides with the time when both mango and palm nut crops are at their most plentiful. Undoubtedly crop raiding must occur and may, despite the close proximity of humans, be a major attraction for the chimpanzees, whose traditional sources of food in this area have been destroyed.
On the other side, east side of the Rift and south of the park is Ndurumu valley. This wide valley has been almost completely deforested and divided into farms (all farming in this area is subsistence farming). Both Tanzanians and Burundians refugees own these farms. Up until the mid-1980s this valley was still extensively forested in Bracystegia species, and formed a natural extension to the Park. Presently, the whole valley has been cleared of most of its natural habitat and farmers are even cultivating crops and cutting trees for firewood and charcoal within sixty metres of the Park boundary.
It is unclear what is attracting the chimpanzees so far from their natural habitat but they have been observed up to 3 km south of the Park boundary and 1 km east. Foreign species such as oil palms, mangoes and bananas are cultivated and along with the relatively low density of more natural food crops such as Strychnos spp. and Holarrhema spp., may well be eaten as has been observed over Ngelwe village.
During March 2000 one researcher was told by two men from Kazinga village that during April 1998 or 1999 two chimpanzees were found dead in their beds in Ngelwe gully. The truth behind this story remains unconfirmed. If true, it would appear strange that two chimps would be found dead in the same area, on the same day, even if they had both died from disease. The fact that it was not reported to GONAPA (Tanzanian National Park employees at Gombe) and no bodies were recovered also raises suspicions that the chimpanzees may have died unnaturally. If this was the case then crop raiding may be a likely motive behind these killings.
Despite being outside the Park's official boundaries these areas have undoubtedly been traditionally part of the southern community's range. During the 1960s no research had commenced on either the northern Mitumba community or the southern Kalande community and therefore the communities' ranges were never a consideration when establishing the Park's boundaries. In hindsight this oversight has been to the detriment of both. Undoubtedly the chimpanzees are extremely vulnerable once they leave the Park at these particular times of year. Their vulnerability in terms of the growing Congolese population has already been discussed. It remains unclear however, if the local population of Burundians in Ngelwe village and Ndurumu valley also traditionally feed on primates.

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