Ecology of the Zanzibar red colobus monkey, Colobus badius kirkii (Gray, 1 968), in comparison with other red colobines - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 245

it is to the geographically closer Zanzibar . b.
kirkii and lringa . b. gordonoum (Struhsaker,
1975, 1981; Struhsaker & Leland, 1980). . b.
rufomitratus and . b. kirkii skulls have the com-
mon fe ature of persistent metopic suture (King-
don, 1971; Brand-Jones in Rodgers et al., 1982).
However, this feature alone does not jusiy link-
ing the two subspecies closely together because it
has been suggested that it is among fe atures
characterisic of drift in small relict populaions
(Brand-Jones in Rodgers et al., 1982). On the
other hand, pelage, facial patten and vocalisa-
ions of . b. kirkii and . b. gordonorum have
higher afiniies with each other than with any
other . badius subspecies (Kingdon, 1971;
Struhsaker, 1975; Struhsaker & Leland, 1980).
Thus these subspecies of red colobus, which have
only recently been isolated from each other, show
highest affiniies.
Today's distribuion of red colobus in Easten
Africa appears to have resulted from both past
climaic changes and human aciviies. The extent
to which human disturbance has helped to mould
tropical African forest ecosystems varies and is
mostly poorly understood. Humans, however,
could have influenced the disribuion of red col-
obus in easten Africa. For example, Rodgers
(1981) reported three sites of past and one of
present eistence of red colobus in areas well out-
side the published range but which are in line
between the ranges of . b. goronorum and . b.
kirkii. Kingdon (1971) and Williams (1966, cited
in Marsh, 1978a) reported . b. rufomitratus in the
Tana River and Arabuko forests, but the monkeys
were later absent in Arabuko Forest (Marsh,
1978a). The absence of red colobus in such areas
where they were previously sighted most likely
results from human disturbances. This may be
elimination by direct killing, since they are con-
sidered a delicacy by local people (Nishida, 1972;
Harper et al., 1974; Marsh, 1978a; Pakenham,
1979; Rodgers et al., 1982). Destrucion and
reducion of their habitat may have reduced and
eliminated the monkey populaions as well.
The range ofall three easten Africa subspecies
has been fragmented mostly as the result of
human aciviies, paricularly agriculture and
selecive felling of rees (Struhsaker, 1975;

l 979a, b, 1981a, b, c, 1985), and there are a
number of brief ecological studies on . b. kirkii
(Harper et al., 1974; Robins, 1976; Struhsaker &
Leland, 1980; Silkiluwasha, 1981; Mturi, 1983;
Swai, 1983) as well as a detailed one (Mturi,
1991). Reports on . b. goronorum are more
scanty (Struhsaker & Leland, 1980; Rodgers,
1981; Wasser, Chapter 13).
This chapter examines the feeding ecology and
some aspects of ranging behaviour and social
organisaion of the Zanzibar red colobus monkey
in comparison with other subspecies of the red
colobus. Comparaive evidence described in this
chapter demonstrates many ways in which habitat
differences and biogeographical isolaion can
generate variability at the subspecific level.

Histoy
The isolaion of some mammals endemic to mon-
tane and forest 'islands' of easten Africa has been
suggested to be attributable partly to a long series
of climaic changes (especially in the late
Qu atenary period) (Hamilton, 1981), and partly
to compeiive exclusion and replacement in the
intervening countryside (Homewood, 1978;
Kingdon, 1971, 1981; Rodgers, Owen & Home-
wood, 1982). These factors also explain much of
the distribuion of the endemic subspecies of red
colobus in easten Africa.
The common ancestor of the three subspecies
of red colobus is generally believed to have spread
rom the western reuge orest of Cenral Africa
along the southern route (Kingdon, 1971, 1981;
Rodgers et al., 1982). The Tana River red col-
obus is, however, supposed to have been isolated
from the others much earlier during the very arid
period 25 000-12 000 years Before Present (BP )
when the forest disappeared (Rodgers et al.,
1982). . b. kirkii and . b. gordonoum are
believed to have become isolated from one
another only recently, when rising sea levels at the
end of the last glacial period, around 10 000 BP,
isolated Zanzibar from the mainland (Rodgers et
al., 1982). These two subspecies are therefore
neoendemic. The Tana . b. uo mitratus is much
closer to the Uganda and westen Tanzania . b.
tephrosceles (Elliot) in pelage and vocalisaion than