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Wasser, personal communication). Throughout
his study, lasing more than four years, Struhsaker
(1975) obseved the Kibale . b. tephrosceles
drinking on only two occasions. In Mahale a male
. b. tephosceles was observed to drink water once
during casual observation (Nishida, 1972). There
have been no reports of drinking among the other
red colobus.
C. b. kirkii
were found to be generally similar to
those reported for the Kibale
C. b. tephrosceles
by
Struhsaker (1975) and Struhsaker & Leland
(1979). The adult male group membership at
these sites was very stable and their social rela-
tionships were close, having strict linear
dominance ranks. Young animals, juveniles and
subadults transferred between groups, mostly
during intergroup encounters. However, groups I
and II were each joined by two solitary C. b. kirkii
subadult males. Starin (1981) reported that in the
Gambia . b. temminckii all females voluntarily
leave their natal group, before or just after
maturity, and most males are forced out of the
group by resident adult males before adulthood.
The Tana . b. ruomitratus migraions were by
adult and subadult females and adult males but
never by independently moving juveniles (Marsh,
1978a, 1979a,b). Clutton-Brock (l 975b) reported
that in Gombe C. b. tephrosceles males trans-
fe rred from one group to another. In all the red
colobus where females transferred (in Tana,
Gambia and Kibale) it has been obseved that
they did so very easily, while adult male transfer
was very difficult.
Group composiion
The Zanzibar red colobus live in heterosexual
social groups (muli-male and female groups), like
most other red colobus studied to date (Clutton-
Brock 1972, 1975a; Nishida, 1972; Struhsaker,
1975; Struhsaker & Leland, 1980; Gatnot, 1978;
Starin, 1981; Wasser, this volume). The excep-
ion is the Tana red colobus (. b. ruomitratus),
which generally live in single-male groups, with a
maimum of two adult males per group (Marsh,
1978a, 1979a, 1981b). The range in number of
adult males per group varied: . b. kirkii had 2-5;
Kibale C. b. tephrosceles, 2-10 (Sruhsaker, 1975);
Senegal C. b. temminckii, 1-13 (Gatnot, 1975,
cited in Marsh, 1979a); and Tana C. b.
uo mitratus, 1 or 2 (Marsh, 1978a, 1979a,
198lb). The number of adult females per adult
male in the bisexual groups of these subspecies
was 5.9, 2.6, 2.0 and 6.6, respecively. Solitary
animals were not uncommon; they were on all
occasions adult and subadult males among, C. b.
kirkii, C. b. tephrosceles and C. b. rufomitratus; in C.
b. temminckii solitary adult or subadult females
were occasionally observed. There were uneven
sex raios in the red colobus which were most
marked in the Tana red colobus followed by the
Zanzibar red colobus.
Like the other red colobus,
C. b. kirkii
group
composition was observed to vary, as a result of
births, immigraions, emigraions and disap-
pearance of animals in the groups. A birth peak
occurred between November and January, when
three-quarters or more of the adult females were
observed to have infants. Infant mortality was very
high: more than half of the infants born did not
survive the first 6 months. This was also reported
by Silkiluwasha (1981).
Group membership dynamics of the Zanzibar
Inraspeciic relaions
In the Zanzibar . b. kirkii relaions between
members of the same group were mostly peaceful.
The same was observed for . b. tephrosceles at
Gombe (Clutton-Brock, 1975b), and Kibale
(Struhsaker, 1975; Struhsaker & Leland, 1979).
However, relationships between adult and
subadult males were generally hosile in Tana
C.
b. uo mitratus (Marsh, 1978a, 1979a,b) and
Gambia . b. temminckii (Starin, 1981)
.
Intergroup relaions varied from tolerant to
aggressive among Zanzibar red colobus, as was
the case for Kibale red colobus (Struhsaker,
1975) and Gambia red colobus (Starin, 1981).
Groups at these localities frequently tolerated the
proimity of another group. There were extreme
cases where two groups mixed and stayed
together (e.g. for as long as 30 min in Zanzibar)
before they separated. In contrast, intergroup
relaions in Tana red colobus were generally
aggressive (Marsh, 1978a, 1979a, b). In all of
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