84 Diet and culture at Sonso
series of manipulations of branches and leaves but is not known to vary systematically
from site to site and has all the appearances of a universal. The same is true of drumming
which, while it varies systematically between individuals, is not known to vary system-
atically between sites.
Leaf-sponging (already referred to above) is perhaps the commonest form of tool-use
we see at Sonso; it too appears to be a universal, occurring at all chimpanzee sites,^26 but
it may yet prove to have cultural components. It was first observed by Duane Quiatt at
Budongo (Quiatt 1994), who went on to make a three-year study of it, from 1996 to
1999 (Quiatt, in press). A total of 111 instances of leaf-sponging were observed either
by Quiatt or by BFP field assistants. Leaf-sponging was often used to collect open water,
e.g. from the River Sonso. Another source of water was from tree-boles mostly access-
ible from the ground. The leaves had been lightly crushed in the mouth prior to use,
increasing their absorbency and maybe releasing flavour. Quiatt also studied unassisted
drinking; only 18 occasions were seen in the same period. Thus Sonso chimpanzees
preferentially drink using leaf sponges; 38 members of the community used leaf
sponges. Several instances were observed of mothers and infants leaf-sponging together;
learning could occur in this context. Acalyphaspp., common climbers in Budongo, were
the species most often used (78/111 cases); the leaves were mostly hairy and thus held
moisture well.
I will end with an example of just how restricted in distribution some cultural features
are. While we were making our 1962 study of the Budongo chimpanzees living at
Busingiro, in the southwest of the forest, we observed one individual male eating tree
ants as described earlier: he sat on or hung from a branch close to the trunk where the
ants were moving up and down, put out an arm so the hand was in the path of the ants,
and after allowing a number of them to crawl up his arm, moved it across his mouth to
eat them. This behaviour has never been seen at Sonso, which is a mere 3 miles due east
across the forest from Busingiro. This is most extraordinary, knowing that females move
from community to community. While I did not record details of ant-eating in 1962, it
may be that this behaviour was confined to adult males, in which case it is easier to
understand its lack of transmission to other communities. The Sonso chimpanzees have
not been seen eating ants, several species of which are common in the forest including
the ‘army’ or ‘safari’ ants of the species Dorylus (Anomma) wilverthi(Schöning, pers.
comm.). The Sonso chimpanzees do, however, eat caterpillars and termites.
(^26) At Mahale this behaviour is listed as ‘present’ (Whitenet al. 1999, 2001) and is thus not common,
customary or habitual at this well-studied site.