(_Cercopithecus æthiops_)
As a familiar example of a very large assemblage of exclusively
African long-tailed monkeys collectively known as guenons (from a
French word signifying to make grimaces), no better species could have
been selected for illustration than the Abyssinian green monkey. This
monkey, which like its cousin the common green monkey (_Cercopithecus
callitrichus_, or _sabæus_) may be seen in almost all menageries and on
many street-organs, is an East African species; whereas the true green
monkey is West African, ranging from Senegambia through Sierra Leone to
northern Liberia, but has been introduced into some of the Cape Verd
and West Indian Islands, where it still occurs plentifully, at least in
Barbados.
From the guereza monkeys (_Colobus_) of Africa, a guenon may be
distinguished at a glance by its well-developed thumbs; while these
monkeys also differ from guerezas, as well as from their Asiatic
relatives the langurs, by having well-developed pouches in their cheeks
for storing food. There is, however, another African group of monkeys,
the mangabeys (_Cercocebus_), some of which are more difficult to
distinguish from guenons, although the majority are recognisable at
a glance by their flesh-coloured eyelids, whence the name of white
eyelid monkeys. When this character fails, resource must be had to the
cheek-teeth, of which the last pair in the lower jaw is less complex in
a guenon than in a mangabey; but to examine the back-teeth of a live
monkey is not an experiment every one would desire to try!
To any one but a specialist, the very large number of representatives
of the guenons are exceedingly difficult to class and identify. The
matter has, however, been somewhat simplified by arranging the species
in thirteen groups, each characterised by the possession of some
particular distinctive feature or features. The well-known diana monkey
(_C. diana_) represents, for instance, a group in which there are
long, upwardly directed, snow-white whiskers associated with blackish
or dark red under-parts, a white brow-band, distinctly white areas on
the chest and the inside of the arms, a chin-tuft, and a white stripe
on the outer side of the thigh. The members of the spot-nosed group,
again, as typified by _C. petaurista_, are recognisable at a glance by
having a large, heart-shaped white spot on the tip of the nose. The
green monkeys, on the other hand, belong to a group (typified by the
Abyssinian species) somewhat less easy to recognise, but characterised
by the absence of black on the outer surface of the arms, which may
be coloured like the body, but are usually, as in the plate, somewhat
paler and grey. The face is nearly always black, but may be mottled or
freckled with pigment; and, except in one species, the whiskers grow
upwards and backwards over the ears. The western species, the aforesaid
_C. callitrichus_, lacks the white brow-band present in the Abyssinian
species and nearly all the other members of the group; the species
forming the subject of the plate being further distinguished by the
black-speckled yellowish olive colour of the fur of the back, the long,
white whiskers, sharply defined from the hair of the rest of the head,
and the presence of a tuft of hair at the root of the tail.
[Illustration]
Guenons may be regarded as some of the most typical of all monkeys, and
those in which monkey-tricks attain their fullest development. They
live more on fruits and seeds than either the guerezas or the langurs,
which feed largely on leaves and the young shoots of trees. Guenons are
indeed probably to some extent omnivorous, whereas the members of the
other two groups are wholly herbivorous. This difference in the matter
of diet is correlated with the presence of cheek-pouches and the simple
character of the stomach in the guenons, whereas the other two groups
lack pouches in the cheek, but, in compensation, have the stomach
folded and divided in a complex manner.
In their native forests green monkeys and their relatives associate
in large troops, which keep up a constant chattering, and each of
which is under the leadership and control of an old male. Each troop
appears to have its own particular territory in the forest; and if one
party intrude on the domain of its neighbour, a fierce contest takes
place, which does not end until the invaders have been driven out or
have proved themselves the stronger. A survival of this custom may
be noticed even among monkeys in a menagerie, where each species or
individual will take up one portion of the cage for its own particular
use, and resolutely defend it against the other occupants of the
enclosure.
From the other members of the genus the patas monkey (_C. patas_) and
its relatives are specially distinguished by their red colouring and
large size, and they should perhaps form a genus by themselves.