The socioecology of interspecific associations among the monkeys of the Mwanihana rain forest, Tanzania: a biogeographic perspective - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 271

period (presumed to be long enough to observe
reliably whether the group contained individuals
from more than one species). Red colobus and
black-and-white colobus were observed most
frequently (50% and 48%, respecively, of all
sighings over the enire study). Sykes monkeys
were the next most frequently observed (26% of
all sighings) followed by the mangabey (13%).
Mangabey sighings were low in part because
these monkeys had a very large home range that
took them out of the area for several months of
the study period.
All species were found in mixed species group-
ings with one another (Figure 13.1). However,
this tendency was most marked between the red
colobus and the black-and-white colobus, even
after controlling for species availabilities; these
two species were found in mixed groups with one
another as often as they were found in single spe-
cies groups (P

cenrated at and above 1000 m. These alitudinal
variaions parallel alitudinal variation in habitat
type described by Lovett et al. (1988). Sykes
monkeys and mangabeys also were common in
disturbed areas at lower elevaions.
We were unable to disinguish between most
social groups of a given monkey species. Based on
the number of sightings per species per unit area,
and several esimates of home range size or these
species throughout Central Africa (Struhsaker,
1975, 1978; Oates, 1977; Homewood, 1978;
Rudran, 1978; Waser, 1984), we esimated a
minimum of 10 red colobus, 10 black-and-white
colobus, 8 Sykes monkey, and 6 mangabey groups
in the study area.

Communiy social structure

Figure 13.l illustrates the percentage of 477
sighings in which each group ype was
encountered for 10 min or more over the study

0.5, Wilcoxon signed-rank test:
see Methods, p. 269). In contrast, both red and

=

0 % Sights � 3 spp.

• % Sights � 2 spp.

a 0.2
:
·:; :. l
" ii
0
: 0
" f
0 .
e 0.1
..

0.0

Red BW Sykes Mang R/BW R/S R/M BW/S BW/M S/M

Group ype
Figure 13. l. Proporion of sighings of each group type over the 11 month study period.
Red=red colobus; BW=black-and-white colobus; S=Sykes monkey; M=mangabey.
Hatched bars represent mixed species sighings that contained 3 or more species.