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 272

black-and-white colobus were found in single
species groups significantly more often than in
mixed species groups with Sykes 'llonkeys or with
mangabeys (P < 0.01 in each case).
Both colobines associated significantly more
often in mixed groups with one another than they
did with mangabeys (P < 0.002 for each com-
parison) or with Sykes monkeys (P < 0.05 for
each comparison; Figure 13.1). Moreover, half of
the mixed groups containing red colobus and
Sykes monkeys also contained black-and-white
colobus; the reverse was not the case (Figure
13.1). Mangabeys and Sykes monkeys were found
more often in single species than in any type of
mixed species group (P < 0.01 for each com-
parison); they showed no significant mixed spe-
cies preerence, with one excepion: Sykes
monkeys were found with red colobus signifi-
cantly more often than with black-and-white col-
obus (P < 0.05; Figure 13.1).
T-tests revealed no significant differences in
the number of individuals per species when
sighted in single versus mixed species groups.
Mean group sizes were: red colobus 23.3 (range
1-75), black-and-white colobus 4.0 (range 1-20),
mangabey 10.2 (range 1-40), and Sykes monkey
3.4 (range 1-15). Mean group sizes probably were
underesimated.

plant par/species over the enire 11 month study
period, using the Shanon-Wiener Diversity Inde:
(Wilson & Bossert, 1971). A list of the five most
preferred plant food species per mokey species is
presented in Appendix 13.1. Differences in
observaion imes prohibited staisical analyses of
between species comparisons. However, within
species comparisons of dietary diversity at the
plant species versus plant part and plant part/spe-
cies levels were possible in Table 13.1; these lat-
ter comparisons reflect the degree to which the
plant part preferences of each monkey species
resulted in increased specialisaion or generalisa-
ion of its diet.
The red colobus diet was more diverse than
that of the black-and-white colobus in terms of
plant food species (row 1, Table 13.1). By con-
trast, plant part preferences of the black-and-
white colobus were more diverse than those of the
red colobus (row 2, Table 13.1). In fact, the
black-and-white colobus is the only species in the
table whose plant part diversity exceeded its plant
species diversity. This also was reflected in the
plant par/species diversiy (row 3, Table 13.1);
only in the black-and-white colobus was the plant
part/species significantly greater than its plant
species diversity (P = 0.025, Chi-square:
Attneave, 1959). These findings are consistent
with other studies of these or related monkey
species (e.g. Struhsaker & Oates, 1975; Struh-
saker, 1978; Homewood, 1978; Rudran, 1978;
Waser, 1984). Overall, the plant par/species
diversity was greatest for the red colobus,

Dieay habis and overlap

The dietary diversiy of each monkey species was
calculated for plant food species, plant part, and

Table 13.1. Shanon-Wiener index of plantood sp ecies, plant part, and plant part per sp ecies diversities
among the orest monkys; number of plant sp ecies in diet as well as proportion of study time each monky
sp ecies was obseved also are listed

Black-and-white

Red colobus colobus Sykes monkey Mangabey

Plant species a 3.08 2.14 2.67 2.50

Plant part a

1.75 2.32 1.66 1.54

3.40 b

3.03 2.30

Plant part per species 3.88

Number of plant species in diet 21 21 16

45

Proporion of study ime 0.32 0.22 0.14

0.32

Note: a The larger value per column in rows 1 and 2 are in bold type.
b Plant par/species diversity (row 3) > plant species diversity (row 1) at the P < 0.05 level.