Food types and food species 55available to the chimpanzees. It would be tedious to describe the foods found in each
forest type but here are some examples of differences:
● Colonizing Forest is characterized by Broussonetia papyrifera(a recently introduced
species) and Maesopsis eminii, both of them much liked foods.
● Mixed Forest contains the majority of food species:Celtis gomphophylla^16 and
Celtis mildbraedii, as well as the many Ficusspecies.
● CynometraForest is characterized by the climax species Cynometra alexandri
which provides food at one time of the year only, normally in the dry season
(January–February).
● Swamp Forest is where the chimpanzees find the fruits of Pseudospondias microcarpa,
the pith of Calamus deerataand the soft woody inside of the stems of dead Raphia
palms,Raphia farinifera.^17
Of these forest types, Mixed Forest was shown by Plumptre (1996) to be the most
common at the present time, constituting about one-half of the forest in the 1990s. This
contrasts with its lesser extent in the 1950s before the bulk of commercial logging for
mahoganies and certain other species, and before the arboricide programme (see
Chapter 1). The increase in the extent of Mixed Forest was a blessing for all the forest
fruit-eating species, including the primates, and has meant that Budongo Forest is
unusually rich in species of fruiting trees such as figs that provide chimpanzees and
monkeys with their preferred foods. Budongo as a whole can today be seen as a food-
rich forest for primates, and this is confirmed by the higher densities of monkeys found
in logged forest and arboricide-treated forest than in unlogged forest such as the Nature
Reserves (Fairgrieve 1995a; Plumptre and Reynolds 1994). Tweheyo (2003) and
Tweheyo et al. (2004) have shown in a 14-month study that most chimpanzee feeding
instances occurred in logged forest, more than in any other forest type.
Whether chimpanzees, like monkeys, have benefited numericallyfrom the logging and
arboricide is less clear. They ought to have done, because of the increase in their food sup-
ply. However, chimpanzees may be less able than monkeys to tolerate the impact of strange
humans working in the forest; a survey of chimpanzees in the forests of western Uganda
(Plumptreet al. 2001) has shown them to be less numerous in Budongo Forest than in
Kibale Forest where the food supply may be less rich, but where human impact over much
of the forest has been less profound. The effects of logging on the primates of different
forests can differ in a number of complex ways (Plumptre and Grieser-Johns 2001).
Food types and food species
The main source of our data on the foods eaten by the Sonso chimpanzees is the ongoing
record of foods seen eaten, recorded by our field assistants and researchers in the course
(^16) Formerly Celtis durandii.
(^17) Budongo Forest does not contain the oil palm,Elaeis guineensis, common in swamp forests of West
Africa. The only area in which it is found in Uganda is Bwamba in the southwest.