58 Diet and culture at Sonso
the detoxification of secondary compounds such as alkaloids than have chimpanzees or
humans. However, chimpanzees can tolerate foods that are more astringent and contain
more alkaloids than humans can.
When working with wild chimpanzees the study of food preferences has to be opera-
tionalized. We can gain a handle on food preferences in the wild by determining the
frequencywith which the animals are observed feeding on particular kinds of foods.
For the Sonso chimpanzees, Plumptre and Reynolds (1994) obtained the order of food
preferences by recording what species and plant parts were eaten during a series of
half-hour scans over a two-year period of observations. The results were as shown
in Table 4.1.
Food preferences were also determined by Newton-Fisher (1999a) independently
of Plumptre’s study. His conclusions, also based on scan sampling, were very similar
(see Table 4.2).
A third independent study (Fawcett 2000) recorded the Sonso chimpanzees’ food
preferences (see Table 4.3).
Finally, food preferences of the Sonso chimpanzees were determined by Tweheyo
et al. (2004) and showed that over a 14-month period (June 2000 to August 2001) chim-
panzees spent most of their feeding time on Broussonetia papyrifera,Ficus sur,F. mucuso,
F. exasperataandF. varifoliaconfirming the findings of other studies and establishing
the importance of fig species in the diet.
These studies show that the preferred (‘favourite’) foods of the chimpanzees of the
Sonso community are Broussonetia papyrifera(Fig. 4.1), Ficus spp. andCeltis
mildbraedii. These findings are very specific to the Sonso community. It is unlikely that
the same food preferences would be found in other communities, even in Budongo
Forest, because Broussonetia papyrifera(the paper mulberry tree) is rarely found in
other parts of the forest, and is lacking in most of the other forests of Uganda. It is an
exotic species introduced by the British in the 1950s around the Sonso Sawmill, to see
if it would grow well there, in the hopes that it might provide wood pulp for paper
production at the mill. It failed to grow to the size needed for commercial purposes
(it remains a small tree in Budongo). But it certainly did take hold where it was planted,
Table 4.1: Food preferences of Sonso chimpanzees (based on
Plumptre and Reynolds 1994).
Species Score Rank Food types
Broussonetia papyrifera 1436 1 RF, FL, YL
Ficus sur 1408 2 RF, UF
Celtis durandii 662 3 RF, UF
Cynometra alexandri 628 4 Seeds
Maesopsis eminii 541 5 RF, FL
Celtis mildbraedii 385 6 YL, RF
Ficus mucuso 379 7 RF, UF
Khaya anthotheca 310 8 Bark
Ficus exasperata 215 9 UF, RF
Cordia millennii 174 10 RF, FL