The lazy, leaf eating, loudmouths of the forest
By Tara R. Harris, Ph.D.
If you haven’t noticed yet, black and white colobus monkeys can be found almost anywhere there is forest. At first glance, black and white colobus are strangely beautiful creatures that seemingly lead rather dull lives. If you take the time to get to know them a little better, however, they turn out to be quite interesting.
Black and white colobus are medium to large-sized monkeys, males average 12kg, that inhabit equatorial forest, mainly in East Africa. Unlike most other arboreal monkeys, they can be quite abundant on forest edges and in somewhat disturbed forest. There are five species in the genus, Colobus, with Colobus angolensis the most common in Rwanda and Colobus guereza the most common in Uganda.
Black and white colobus are visually striking animals, with black bodies, flowing white capes of hair down shoulders or their backs and sides, as well as long black tails with a white tuft at the end that looks a bit like an artist’s paintbrush. Beauty comes at a price, however - black and white colobus monkeys have been hunted throughout history for their unusual skins. They have been used in numerous East African cultures as adornments for warriors and weapons. Unfortunately for the monkeys, they also came into fashion in Europe in the late 1800s, as well as in the early 1970s, and it is reported that over 2 million skins were imported from Africa and made into coats.
Despite the locally intensive hunting pressure the colobus have sometimes faced, they have managed to survive and reproduce successfully, at least in protected areas where there is a constant supply of leaves. Leaves make up 50-90% of their diet and they have a large 4-chambered stomach and special bacteria to help them digest their high-fiber meals. They also feed on a number of unusual items, where they are available. Colobus angolensis feed relatively heavily on lichens and Colobus guereza (“guerezas”) often travel long distances to feed on the bark of eucalyptus, a non-native tree that happens to be high in sodium. Guerezas also sometimes enter peoples’ kitchens to eat leftover charcoal or ash, and to lick the concrete. These strange habits may provide them with necessary minerals, regulate their stomach pH, or help neutralize toxins.
Black and white colobus form groups that range from small - guereza groups average 6-9 individuals - to extremely large - Angolan colobus in Rwanda sometimes form supergroups of more than 300 individuals. When a new infant is born, it is a big deal. Newborns are completely white, except for a pink face, and usually all the group’s females - even little juveniles - want to hold them. Sometimes, this allows the mother to gain valuable feeding or resting time, but there are a lot of incompetent babysitters and infants sometimes get held upside down by their tails or even dropped from high in the trees. Such negligent behavior is actually a major source of infant mortality.
Black and white colobus sometimes fall prey to crowned hawk eagles, leopards, chimpanzees, and even dogs. When the monkeys spot a predator that is an immediate threat, the group’s adult males snort at it and roar loudly, sometimes running and jumping through the treetops. Adult males produce these same roars as intergroup communication nearly every morning between midnight and dawn during choruses. The roaring typically starts somewhere off in the distance, and spreads like a wave throughout the forest until nearly all the males are roaring. The length of a male’s roars are indicative of his fighting ability, and the auditory frequencies of a male’s roars also contain information about his body size, relative to other colobus. Males’ roars, made using an unusually large larynx and air sac, exaggerate their body size relative to other species - a trait that may have initially functioned in intimidating predators.
Where colobus densities are high, groups, and especially adult males, fight each other frequently. When groups approach, males threaten one another by clicking their tongues and sticking out their legs, a display called “stiff legs.” If groups don’t back off, males often chase one another all over the forest. When a winner is not easily decided, and the contest drags on for hours, sometimes these lazy monkeys simply decide to take naps near one another and resume fighting when they wake up. The point of all of this aggression seems to be access to high quality food, with males securing feeding areas for their mates and offspring.
Black and white colobus monkeys can be a bit shy and difficult to observe, but there are several tourist spots in Rwanda and Uganda where they are used to people. In the mountains of western Rwanda, Colobus angolensis can be seen in the Nyungwe Forest, where they are sometimes found in exceptionally large supergroups. In Uganda, the best places to see Colobus guereza are Lake Nkuruba - a community-managed forest fragment/campsite near Kibale National Park and Sebitoli - a small tourist camp at the northern end of Kibale National Park, near Fort Portal. Undoubtedly, there are other places as well, so keep a look out for them - or listen for them - whenever you are near the forest.
