4. Diet and culture at Sonso
BobRachel — the small and tiny orphans — wandering alone. But fine. They join up with Nkojo
& Bwoba. We follow all 4 for ?1 km along trails and through blocks. Somewhat punishing pace but
we keep up with them & arrive at destination — a Morus lacteatree to the west of camp. Now
a med. sized gp (10–15 indivs) all feeding on Morusfruits, small but abundant. 8.33 Calls to SW,
ours reply. 8.40 Nkojo, Black descend and move towards SW. Others stay. KalemaKumi. 8.44.
Jambo down, Nambi down, then others, now all are descending, quite a long and difficult descent
but each makes its own route down. In some cases takes 2 mins to descend (14 March 2002).The chimpanzee’s day is 12–13 hours long, and of those hours about half, some
6–8 hours each day, are spent foraging and feeding. They start the day feeding in the
company of the chimpanzees that have nested nearby, then either move to a new feeding
site with one or more of them or head off on their own to join a new group. Sometimes
they are guided in their movements by calls coming from groups in other areas of the
forest. If they are on a tree with an abundance of ripe fruits they pant-hoot in chorus. If
they hear a chorus from over the canopy they stop feeding and listen attentively, some-
times replying. We consider the vocalizations of the Sonso chimpanzees in more detail
in Chapter 6.
If food is scattered widely then individuals can forage most successfully on their own
or in small groups, thus reducing competition. In these circumstances, chimpanzees
tend to be rather quiet; on the other hand, if food is concentrated in one location, as
when a single Ficus mucusotree is fruiting heavily, there is enough food for many
chimpanzees to gather there to feed. Indeed, their vocalizations are loudest and their
pant-hoot chorusing is most frequent when many of them are concentrated in a large
party on a single tree. We deal with the topic of party size in relation to food availability
in Chapter 5.
Forest types and chimpanzee foods
As described in Chapter 1, there are four forest types: Colonizing Forest, Mixed Forest,
CynometraForest and Swamp Forest. These forest types have different tree species
compositions and therefore the foods of chimpanzees differ from one forest type to the
other. Thus the composition of the forest determines the range of feeding possibilities