many universities, would be a considerable task. In the preparation of this book I have
used my own data and, with permission, data collected by other researchers and senior
scientists. I have also drawn from data files compiled by our field assistants, such as our
meteorological data files or files that contain data on the species of trees that provide
chimpanzees with food, or the distribution of those trees in the forest. I have also
used maps and photographs, and last but not least the copious notes in my own field
notebooks.
Range and density of the Sonso community
The BFP camp, located in a large clearing in the heart of the Budongo Forest made orig-
inally by Budongo Sawmills Ltd, is in the middle of the range of the Sonso chimpanzee
community. We could not have found a better location if we’d tried. Our trail system
radiates out in all directions from camp, and we find Sonso chimpanzees to the north,
south, east and west of it (see Fig. 1.1).
Reynolds and Reynolds (1965) estimated the range size of the Busingiro community
to be 6–8 square miles (15.5–20.7 km^2 ), and we estimated that within that range there
were some 60–80 chimpanzees. This gives a density of 3.9 chimpanzees/km^2. A later
study by Sugiyama (1968: 243) put the density of the chimpanzees in the Busingiro
region higher, at 6.7/km^2.
The home range^5 of the adult male Sonso chimpanzees was investigated by Newton-
Fisher (2002b, 2003) over a period of 15 months in 1994–95. This study was based on
the ranging behaviour of adult males, who move over the whole home range of the com-
munity. Wrangham (1979) first suggested that male chimpanzees at Gombe Stream
Reserve had a home range that was 1.5 to 2 times greater than that of females, because
males jointly patrol the borders of the community’s territory whereas females tend to
avoid the border areas. In addition, at Gombe, Wrangham found females to be less
sociable than males, so that females were dispersed relative to males within the defended
territory. The same difference between male and female range use was found by
Chapman and Wrangham (1993) in the Kanyawara community of Kibale Forest
Reserve, Uganda. This pattern of chimpanzee range use has been much debated and
may not apply at all chimpanzee sites, e.g. at Taï in West Africa described by Boesch
(1991) and Boesch and Boesch-Achermann (2000), where female and male ranges
are the same. Females have never been found to have larger home ranges than males
and so Newton-Fisher’s focus on males is wholly justified. All males need to be
included, because use of the home range is not equal from individual to individual
(Newton-Fisher 2003).
Home range is defined by Newton-Fisher as that part of the range that is habitually
used, i.e. it does not include the less frequently used parts of the range where it borders
on the ranges of other communities. He calculated the home range at the time of his
28 The Sonso community
(^5) We should remember that the home range of a community of chimpanzees shifts from year to year: at the
time of writing the Sonso chimpanzees seem to be extending their range in a southeasterly direction and may
be reducing it to the southwest (N. Newton-Fisher, pers. comm.).