Angolan Colobus, Colobus angolensis
ANGOLAN COLOBUS
Colobus angolensis
Geographic Distribution and Habitat
The Angolan colobus, also called the Angolan black-and-white colobus, primarily inhabits the lush canopy of African forests, which complements their remarkable agility and tree-climbing skills. These strikingly beautiful primates can be found throughout central Africa, with a range that extends from Gabon and Cameroon in the west to Ethiopia in the east, all the way to southward Tanzania. Angolan colobuses are quite adaptable and can thrive in various forest types, including lowland, bamboo, coastal, and montane—though they prefer dense rainforests and tropical climates. Aside from forests, they have also been found living in savannas and even swamplands!
Angolan Colobus monkeys are part of the Colobus genus, which includes six species and seventeen subspecies.
Size, Weight, and Lifespan
Sleek, moderate-sized, and adorned with lengthy, graceful tails, the main form of sexual dimorphism within the Angolan colobus monkeys is their size. Females typically reach a head-body length of approximately 18 inches (46 cm), accompanied by a tail measuring about 18 inches (46 cm) in length. Males have a head-body length of around 28 inches (71 cm) with a tail extending up to 35 inches (89 cm). Carrying on with this size difference, adult females weigh around 13 pounds (6 kg) on average, while males can weigh almost double, capping at around 24 pounds (11.4 kg).
These monkeys typically live up to 20 years in the wild but can reach around 30 years old in captivity.
Appearance
An absolutely eye-catching species, Angolan colobus monkeys are characterized by shiny black coats paired with a long, white mantle of fur that frames their face. This fur almost appears to have a “blowout” style, curving inwards at the end and forming a border around their small, round faces. More white fur falls down their sides almost in a mullet fashion; sometimes this plume of fur is compared to an elegant epaulet.
These primates exhibit unique proportions, with their hind legs being longer than their forelimbs, which contributes to them being so skilled in forest canopy maneuvering. Their flattened nails also serve to further enhance their arboreal prowess. Another notable feature is the distinctive pads on their bums, an adaptation that is common among species who often sit on hard surfaces. As I’m sure you’d assume, these pads offer some comfort, but more than that, they also provide balance assistance for when the Angolan colobus monkeys are sleeping in the trees.
Newborns are born with delicate pink faces and pure white coats, which gradually transition to the iconic black-and-white coloration over a span of around 3 months.
Diet
Unlike most African monkeys, Angolan colobuses do not have cheek pouches. Instead, they have sophisticated digestive systems that include a three-chambered stomach, which holds specific bacteria that can ferment and digest leaves efficiently. Because of this, they are able to eat a number of substances that are toxic or indigestible to most other primates, including unripe fruits, flowers, and cellulose-rich, mature leaves.
These primarily folivorous monkeys are known to consume over 45 different species of leaves, as well as stems, bark, buds, shoots, and even the occasional insect. Because a majority of their diet is low in calories and nutrition, Angolan colobuses have to spend most of their daylight hours foraging in the canopy, sometimes consuming up to 7 pounds (3kg) of leaves in a day!
One benefit of being an Angolan colobus is that they don’t have to worry too much about competing for food, because they are the primary residents of their canopy and most of their diet is toxic or indigestible to other monkeys.
Behavior and Lifestyle
Angolan colobus monkeys exemplify an arboreal lifestyle, really only leaving the comfort of their canopy for an occasional forage along a stream. As diurnal creatures, they spend the daylight hours navigating treetops, using their lightweight bone structure, balancing tail, and elongated limbs to leap from branch to branch—sometimes covering an impressive distance of up to 50 feet (15.2 meters). This is an astounding feat, as few other primates are able to rival them in their tree-climbing and branch-leaping abilities. Their Cirque du Soleil level stunts are made possible by their long tails assisting with trajectory and their mantles function as an ersatz “parachute” to slow them down as they land.
When threatened by predators, such as leopards or eagles, a male Angolan colobus will roar to emit a warning signal, allowing the rest of their troop to disperse safely.
Angolan colobus monkeys have rudimentary, almost absent thumbs. Their long hook-like fingers facilitate brachiation, a form of arm swinging from branch to branch. Thumbs would get in the way!
These monkeys sometimes eat clay found in termite mounds, which researchers assume may further help with their ability to process toxins.
Angolan colobus monkeys typically live in small, cohesive troops of around 6 females and their offspring, led by a dominant male. With this being said, there have been troops of over 300 members observed in Rwanda’s Nyungwe forest. This phenomenon is rare and is believed to be attributed to the plethora of mature, abnormally nutritious leaves in the area.
These troops exhibit territorial behaviors, defending their range of habitation from other groups of colobus. The role of the dominant male revolves around territorial defense and predator protection, while females hold leadership roles within the troop.
Females tend to remain within their natal group for life, while young males depart before maturity to establish their own troops or challenge existing dominant males, which unfortunately increases the chance of infanticide occurring, as tensions grow between competing males. If a new male succeeds in taking over the troop, he will likely kill the babies to force their mothers into estrus so that they will be willing to mate with him, allowing him to pass his genes along to future generations.
Altercations over mates are rare with these monkeys. Within the troop, members collectively care for infants, with all adults engaging in playful interactions with juveniles as they mature.
Though somewhat less diverse than some other primates, Angolan colobus monkeys still possess an array of communication methods to convey important information within their troop. Dominant males will often showcase a nice handful of roars in the morning, possibly serving to reinforce territorial boundaries.
As mentioned earlier, males will assume a protective role by roaring and sometimes even jumping to ensure their troop retreats to safety in the face of a predator. Additionally, squealing, purring, tongue-clicking, and yawning are all communication techniques that can signal threats or distress.
In the polygynous social structure of Angolan colobus monkeys, dominant males maintain control over reproductive females, waiting for them to indicate their readiness for mating. Mating occurs year-round, though peaking during the rainy season, leading to most births taking place in September and October. Gestation typically lasts between 147 and 178 days, with single offspring births, aside from the occasional twins.
Though mothers typically keep their infants close, carrying them on their abdomens, they allow for co-parenting amongst the troop. Infant weaning occurs at around 15 months. Females reach sexual maturity at two years and males at four years.
Because of the leaf matter and fruit in their diet, Angolan colobus monkeys help with dispersing seeds and stimulating new plant growth. Furthermore, they provide food for their natural predators: eagles and leopards.
The Angolan colobus is classified as Vulnerable (IUCN, 2016) by the International Union for Conservation of Nature, appearing on the IUCN Red List of Threatened Species.
They face significant threats, primarily stemming from habitat loss and hunting pressures. These monkeys have been excessively hunted for their prized fur, enough to lead to localized extinctions within certain areas. Due to the monkeys ‘ substantial size, the species is also a hunting target for bushmeat, primarily in Central Africa.
While hunting has significantly contributed to the decline in population, the most pressing threat today is habitat destruction. As with most primates, we have humans to blame for the loss of their homes. As human populations grow, we have taken over their environments to create more space for our agriculture and infrastructure developments. Furthermore, many of these monkeys have fallen victim to car-induced deaths.
Unfortunately, it is estimated that the Angolan colobus population size has decreased by over 30% within the past three generations.
Angolan colobus are listed in Appendix II of the Convention on International Trade in Endangered Species (CITES), an international agreement between governments whose goal is to ensure that international trade in specimens of wild animals and plants does not threaten their survival. This means that while there are no immediate threats of extinction, close monitoring of the species is called for.
They are completely protected within the Democratic Republic of the Congo, meaning they cannot be hunted.
Colobus Conservation, a non-profit organization dedicated to safeguarding the Angolan black-and-white colobus monkey and other primates within the southern coast of Kenya (mainly in Diani), was established in January of 1997 in response to growing concerns among local residents about the impact of human development on primate populations. With their help, we have seen habitat preservation, community engagement, educational initiatives, and more.
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Written by Hanna Broadland, March 2024