After that, increases and decreases in the population of the Sonso community were
due to births, deaths and migration rather than recognition of new members. The mem-
bers of the Sonso community as it is now, including residents, infants born into the com-
munity, immigrants, and those who have died or disappeared, from the beginning of our
studies to the time of writing, together with some details of each individual, are listed in
Appendix A. In all, over the time since our studies began in the early 1990s, including
all individuals, many of whom have died or disappeared, we have named 85 chimpanzees.
To date the community size has fluctuated between 48 and its present size at the time of
writing, which is 62.
Habituation
The process of overcoming the natural fear animals have of people, and reaching the
point where they no longer flee when we human beings arrive, is called habituation. At
some chimpanzee study sites, notably the Japanese-run project in the Mahale Mountains
of Tanzania, to the south of Gombe, and to some extent at Gombe itself, habituation was
achieved with the use of food put out for the animals, a technique known as provision-
ing. This technique of gaining the confidence of animals was developed by Japanese
primatologists in Japan in the 1950s during their pioneering studies of Japanese
macaques.
Tutin and Fernandez (1991) investigated the process of habituation to researchers by
gorillas and chimpanzees at the Lopé Reserve, Gabon. Despite the extra difficulty and
time taken to find the animals, they decided not to use provisioning, which affects the
apes’ natural feeding behaviour and, in the case of gorillas, can lead to charging displays
by adult males. Instead their method was to follow the apes and gradually break down
their fear through frequent contacts. Grieser-Johns (1996) highlighted a particular
difficulty with habituating chimpanzees (at Kibale Forest), namely that because of their
fission–fusion social system one does not see the same individuals each day and so the
process of gaining familiarity takes longer than it would otherwise. She also noted that
adult females were shyer than adult males, as we found at Budongo. The researchers at
Kibale, like those at Lopé, have not used provisioning.
At Sonso we took the decision early on not to provision the chimpanzees. While this
makes habituation harder, it has become apparent that provisioning chimpanzees has
effects on their feeding ecology because it steers them in their daily movements towards
the provisioning site and thus their natural foraging methods are disrupted. Also, in
some cases it has caused outbreaks of aggression because the concentration of food in
one place has increased the level of feeding competition between the animals. Power
(1991) has argued at book length that provisioning can have widespread and quite dev-
astating effects on the behaviour of chimpanzees, leading to violence between adults
and against infants. What really seems to happen if food is artificially provided is that
the increasing competition leads to outbreaks of violence, as Power suggested.
However, there have now been many documented cases of violence between adult chim-
panzees, and violence directed against infants, in communities that have never been
Habituation 25