Chimpanzees of the Budongo Forest : Ecology, Behaviour, and Conservation

daily at our Sonso camp in the middle of the forest for over 10 years. Rainfall varies
between 1240 mm and 2187 mm per annum with a mean of 1600 mm. Its distribution
over the year has a bimodal pattern with most rain falling between March and May and
again between September and November (Fig. 1.2). There is one major dry season,
between mid-December and mid-February when rainfall normally drops below 50 mm
(and in some years below 10 mm) a month. At the height of this dry season, in January,
the forest becomes hot and dry inside, leaves crunch underfoot and the trees begin to
look weary and lifeless. At this time too the wildlife suffers from the daytime heat and
chimpanzees, for example, spend much of the middle of the day down on the forest floor
in areas of deep shade; their food supply is also depleted at this time. The minor dry
season is around June–July when again the food supply is diminished. The combination
of two dry seasons alternating with two wet seasons gives the Budongo Forest its
characteristic bimodal pattern (Fawcett 2000).
Temperatures are rather even during the year, with an upturn in the dry season.
Monthly maximum and minimum temperatures vary between 32C and 19C.

Disease and the human population

During the twentieth century Budongo Forest was expanding along its southern border,
colonizing the surrounding grassland with a mixture of tree species, notably Maesopsis.
In the twenty-first it is being cut back by encroaching settlers and refugees from the

10 The Budongo Forest

300

30

20

10

0

Rainfall

Maximum temperature

Minimum temperature

250

200

150

100

50

0

Rainfall (mm)

Temperature (

°C)

JanuaryFebruaryMarch

AprilMayJuneJuly

August

September

OctoberNovember

December

Months

Fig. 1.2: Monthly rainfall and temperatures collected by BFP from 1993 to 2000 (from Tweheyo
et al. 2003).