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 261

aggressive encounters with other conspecific
groups, or with predator or compeitor species.
Transfer from one group to another is very
difficult for adult male red colobus. It involves a
lot of aggression as reported in the Tana (Marsh,
1978a, 1979a) and Gambia red colobus (Starin,
1981). These aggressive encounters sometimes
cause injuries which may eventually result in
death. Killings are not uncommon in aggressive
encounters during male transfer in Gambia
(Starin, 1981). The red colobus in Tana tolerate
one or occasionally two adult males in a group
while the rest are forced to range in unfavourable
areas. They eventually become unhealthy and
someimes die as a result (Marsh, 1978a, 1979a).
ll these factors account for a higher mortality
rate amongst males, which may result in the
unequal sex raio seen

ranging patterns both beween and within the
subspecies of red colobus. Ranging patten vary
from total range overlap to exclusive use of range;
intergroup aggression increases in the same
direction. Such variaion is also reported in other
colobines (Presbytis entellus: Jay, 1963; Yoshiba,
1968; P. melalophos: Bennett, 1983; Colobus
guereza: Dunbar & Dunbar, 1974; Oates, 1977)
and in other primates, including Cercopithecus
aethiops (Kavanagh, 1981) and Pap io ursinus
(Hamilton, Buskirk & Buskirk, 1976). Various
explanaions have been proposed or these dif-
ferences, all relaing to the environment, includ-
ing differences in degree of predation pressure,
range size, population density, and disribution
and abundance of food. Therefore, it is not sur-
prising that in red colobus variation occurs even
within subspecies.
The Tana red colobus exhibit high exclusive
range use, male intolerance and uneven sex raio
compared to other red colobus. Such behaviour
pattens may eventually lead to morphological
changes such as sexual dimorphism. For instance,
it has been reported that body size dimorphism in
red colobus is slight or lacking (Lentenegger
Kelly, in Marsh, 1978a), but this may not apply to
the Tana red colobus (Marsh, l 978a).
All red colobus subspecies showed polyspecific
associaions with primates symparic to them. The
ype of activities performed during such associa-
tions suggest that they were not always chance
affairs but were sometimes deliberate acts. Even if
they happened by chance, whenever they
occurred they appeared to be encouraged, based
on the type of aciviies which occur when dif-
ferent species come together (e.g. mutual groom-
ing and playing). The monkeys form polyspecific
associaions as they gain many of the advantages
of social life such as grooming (especially in soli-
tary individuals) and efficiency of predator detec-
tion and feeding. Moreover, the disadvantage of
interspecific competiion for resources like ood
and mates at times may be quite low. Polyspecific
associaions are further discussed in the ollowing
chapter by Wasser (this volume).
In conclusion, the informaion gathered here
illustrates how habitat and phylogeny can interact
to yield the comparaive differences and similari-

these red colobus

m

monkeys.
Mar s h (1978a, 1979a) suggests that the
extreme sex raio within groups of the Tana red
colobus is attributable to high extra-group male
mortality related to the marginal nature of their
habitat. He adds that seasonal maing in the
Senegal red colobus (in Fathala, a habitat similar
to Tana) increases the cost-benefit raio to
dominant males, excluding others to a point at
which the behaviour is maladapive. Thus they
have more than one male in a group. This sugges-
ion has support from the Zanzibar red colobus
study. The Zanzibar red colobus in Jozani, a
habitat similar to Tana (Kenya) and Fathala
(Senegal) and with seasonality in birth like the
Fathala red colobus, has muli-male and female
groups (see also Wasser, Chapter 13). However,
the Kibale red colobus exhibits aseasonal births
and muli-male groups (Struhsaker, 1975).
The high permeabiliy of groups of red colobus
could be explained in terms of avoidance of
inbreeding. In those groups with mobile adult
males, adult females with infants or those that are
pregnant may move to prevent their infants from
being killed by immigrant adult males, as in the
Tana (Marsh, 1978a, 1979b) and Gambia red
colobus (Starin, 1981). Adult female transfer may
also be related to mate choice (Marsh, 1979b;
Starin, 1981).
There is variaion in intergroup relations and