The Colbus is a fairly widespread inhabitant of Africa with olive, red and white varieties and a wide variation within those principal divisions. The Guereza Colobus in East Africa is regarded a sthe Eastern Variety, differing from the Western Variety which is Colobus angloensis, or the Angola Pied Colobus.
Colbus monkeys are to be found all over tropical Africa from the primate rich forest habitats of the Gambia in West Africa to the fertile coastal ecology of Zanzibar island on the east coast of Africa. The less adaptable red and olive colobus species tend to be confined to the surviving blocks of equatorial forest while the more versatile black and white varieties are to be found within a wider variety of habitats.
A particular curiosity of the colobus monkey is its ruminant-like digestive system that allows it to feed on the mature leaves of a very few different species of tree, thus widening the scope of possible habitat and narrowing the range of territory that each troop might require. Thus colobus monkeys, although tending to troop sizes of no more than 10 individual animals, are able to survive on limited natural resources in large numbers.
Apart from the striking coloration and decoration of this creature, perhaps sits most striking characteristic is its enlarged stomach that is divided into chambers wherein ingested vegetation undergoes and extremely thorough bacterial fermentation and pre-digestion. This also allows colobus monkeys to east leaves and other plant material that might be poisonous to other monkeys. This evolution of a rumen-like digestive system has allowed the colobus to occupy a series ecological niches that have been largely inaccessible to other species of monkey.
The nexus of this is the ability of the colobus to subsist off the coarse mature leaves of a limited number of tree species, reducing the amount of energy required to search for food and reducing the area within which that search must take place. Thus the colobus spends a great deal of its time stationary in the act of feeding, and has as such evolved the very taciturn and ‘thoughtful old man’ posture that characterises it.
In the Grumeti Wildlife Reserve of the Serengeti it is rare to take a morning game drive along the Grumeti River without seeing at least one of these creatures. Usually a small troop is encountered with the dominant male and his attendant females sitting high in the tree canopy, thoughtfully chewing their leafy breakfast and pondering their visitors with an idle curiosity.
The colobus of the upper Grumeti River, or at least those that I have frequently encountered, tend not to fear the intrusion of humans into their habitat, but if we approach too closely they will, with a surprising turn of speed, begin to move away through the canopy. On occasions the spectacular ‘leap’ for which the colobus is well known.
A few facts about colobus monkeys:
- The colobus social unit is a family of some 10 individuals led by a dominant male and populated mainly by females and young. A second, peripheral male may be tolerated in order to avoid the stress and confrontation of ejection. Usually female offspring remain with the natal group while males are forced to leave upon maturity to either join or start a new troop.
- Colobus family groups are very close knit and cohesive, although some hostility is expressed towards neighbouring or overlapping troops.
- The black and white colobus has the largest larynx in the sub-family. As a consequence a rolling bass baritone call is the characteristic vocalisation of the colobus.
- Besides this, and like most monkeys, colobus display a high range of visual, vocal and olfactory signals for communication a variety of emotions, warnings and other communications.
- Pied colobus species can go for long periods without drinking, drawing all the necessary moisture for their diet from plant material
- Colobus troops are characterised by an extremely low level of internal aggression or squabbling
- Colobus monkeys are unique in having almost no thumb capacity
- An unusual feature of colobus social relations is the general handling of infants by members other than the mother from a very young age
- The roar of the colobus monkey is one of the loudest natural calls, rivalling the new world howler monkey.