68 Diet and culture at Sonso
have uses of one kind or another as timbers; the list reads like a list of chimpanzee foods.
There is one tree species that is primarily, maybe only, dispersed by chimpanzees. This
isCordia millennii, a fine forest tree, present in Budongo and some of the other forests
in Uganda where it is also dispersed by chimpanzees, e.g. Kibale Forest at Kanyawara
(Chapman, pers. comm.) and Ngogo (Mitani, pers. comm.). The wood of this tree
has been traditionally (and still is) used for the manufacture of boats on Lake Albert.
Kityo and Plumptre (1997) in their handbook on timber species of Uganda write of
this species:
This light brown, open grained timber is greatly sought after for boat-building, both for planked
canoes and for dugouts. It is soft and easy to work, is highly durable in water, very impermeable to
water movement and, therefore, slow to dry and to absorb water. It also shows extremely low
shrinkage on drying and consequently does not crack easily in the sun and with changes in humidity.
Its properties are ideally suited to boat-building and since it is available only in small quantities it
is best used for this purpose.Katendeet al. (1995) add that boats made of Cordiafloat if overturned.
The reason why chimpanzees are the main or even sole dispersal agents of this tree is
found in the nature of its seeds. The fruits look from the outside like large oak acorns.
Eggeling (1940b) describes the fruits as follows: ‘Fruit ovoid, 1 –1 in. long, about
in. diam., cupped by the enlarged calyx.’ These fruits begin life green and later turn
yellow. The outer husk is shiny and hard, but inside the flesh is sticky and slippery, the
consistency of sticky jelly. This sticky jelly is very firmly attached to the seed, which is
large and very hard and is located in the middle of the fruit; the seed is about an inch
long and thus a large item to swallow.
Chimpanzees are very fond of this species, eating it at both the green and yellow
stages. They spit out the husk and most of the large seeds after eating the flesh, but evid-
ently the slippery jelly causes a number of seeds to be swallowed, with the result that
when they have been feeding on Cordiawe find one or more seeds (as many as six in a
large sample) in their dung. Monkeys also eat Cordiabut do not swallow the seeds; in a
one-year study of blue monkeys (Cercopithecus mitis) at Budongo, Fairgrieve (1995a)
only once found a Cordiaseed in the dung. At times it has been suggested that hornbills
and fruit bats disperse Cordiaseeds but this has not been borne out by research findings.
For hornbills the fruits are not eaten (Kalina 1988), and in the case of fruit bats (a) they
prefer soft fruits to eat, and Cordiafruits have a hard outer husk when on the tree, and
(b) fruit bats find their food by smell and Cordia fruits do not smell when on the tree
(Robert Kityo, pers. comm.).
In 1995 Chris Bakuneeta, Kirstin Johnson, Bob Plumptre and I wrote a paper about
human uses of tree species whose seeds are dispersed by chimpanzees in the Budongo
Forest (Bakuneeta et al. 1995). Of the many tree species whose seeds are dispersed by
chimpanzees, not all are used by people, but a number of them are, and we were inter-
ested in showing the contribution made by chimpanzees to the local human population
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