Geology Reference
In-Depth Information
correlate significantly with the overall abundance
of these items, but a correlaion was found for
young leaves (r5
by Tana and Zanzibar, one by Kibale and
Zanzibar, and five by Tana and Kibale red col-
obus. Examinaion of beta diversiy, i.e. diversiy
between communiies, revealed that tree species
found in the habitats of the monkeys are generally
different. Thus the low diet overlap may be attri-
butable to high beta diversity among the habitats
of the monkeys.
There were, however, cases where a plant spe-
cies was present yet was ignored by the red col-
obus, although it was consumed by red colobus
elsewhere. For instance, Phoenix relinata Jacq.,
found in Tana and Zanzibar, was not eaten by red
colobus in Tana while the Zanzibar red colobus
consumed its fruits with relish.
Pluchea discoies
(DC.), found in Tana and Zanzibar, was used
only by the Tana red colobus. There were similar
cases at generic level. Anthocleista schweinfurthii
Gilg is found in Gombe and was eaten by the
Gombe red colobus, consituing 6.3 % of the
diet. A. grandiora Gilg is abundant in Jozani
Forest Reserve, Zanzibar (2.33% relaive densiy
and 2.86% canopy index), but was not fed upon
by the Zanzibar red colobus. Two other genera
were found in both Gombe and Zanzibar but were
observed to be consumed only by the Gombe red
colobus. There are three Diospy ros species in
Zanzibar, none of which was observed to be
eaten; a fourth species, D. mespilomis (Hochst.)
A. DC., found in Tana but not in Zanzibar, was
the least preferred food (0.8% of the annual diet)
by the Tana red colobus, although it was the most
abundant ree in Tana (canopy index 23.7%).
Another Diospyros species was fed on by the
Kibale red colobus (0.14% of diet), however,
D.
natalensis
(Hav.) Brenan, found in both Tana and
Zanzibar, was not consumed by the red colobus
monkeys in either locaion.
0.618, P < 0.05). A significant
correlaion might be expected when the use of an
item is consistently limited by its abundance;
failure to show such a correlaion resulted from
the lack of seleciviy of the monkeys in the choice
of these food items relaive to others.
Seleciviy was examined further by ploting the
monthly conribuion to the diet of six items as a
uncion of their abundance indices (see Figure
12.3). Preferred food items that had marked
(seasonal) variation in their abundance were
heavily consumed when they were abundant (e.g.
leaf buds, flowers and flower buds).
Monthly variaion
n
food species and item
contribuion to the diet was reported in other red
colobus studies (Clutton-Brock, 1972, 1975a;
Sruhsaker, 1975; Marsh l 978a, 1981a; Gatnot,
1978). As in this study, they showed that the vari-
aion was influenced by the abundance of specific
food items and their preferences by the monkeys.
=
Other food habits
Idioyncrasies of diet
Diferences in the acceptabiliy of food to three
subspecies of the red colobus were examined by
considering Kibale (Sruhsaker, 1975), Gombe
(Clutton-Brock, 1975a), Tana (Marsh, 198la)
and Zanzibar (this study), all of which showed
some diet overlap at both species and genus level.
For instance, 11 plant food species were used by
two or more subspecies of red colobus. Of these,
Albizia gummifera was eaten by the red colobus in
all the above studies; A. glaberima by all except
Kibale red colobus; Ta marindus indica and Anti-
esma venosum by Tana and Zanzibar; itex
oniana, Bielia micrantha
and
Syzygium cumini
by
Zanzibar and Gombe;
Bligh ia unijugata
Bak. and
Harrisonia abyssinica
Oliv. by Tana and Gombe;
and Ficus mucuso by Kibale and Zanzibar red col-
obus. Table 12.7 summarises dietay overlap
among these subspecies of red colobus. There
were 12 cases of overlap at the generic level: one
genus was used by all red colobus, four genera by
the Zanzibar and Gombe red colobus, one genus
Animal food
Foraging for animal food has not been reported
with certainty in any red colobus. There was,
however, a suspicion that the Zanzibar red col-
obus diet included invertebrates: the monkeys
were occasionally observed to pick up and eat
unidenified items from both dead and living tree
runks, which did not appear to have fungi or
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