WESTERN RED COLOBUS
Geographic Distribution and Habitat
The western red colobus, also commonly known as the Upper Guinea red colobus, is a species of Old World monkey found along the coast of West Africa in fragmented populations that span the countries of Côte d’Ivoire, the Gambia, Guinea, Guinea-Bissau, Liberia, Senegal, and Sierra Leone. They prefer primary or mature old growth forest, but they live in all levels of the tree canopy from moist forest to gallery forest alongside streams or rivers.
There are two subspecies of the western red colobus monkey. The bay colobus, Piliocolobus badius badius, occurs in fragmented populations in Sierra Leone, southern Guinea, Liberia, and western Côte d’Ivoire. Temminck’s red colobus, Piliocolobus badius temminckii, occurs in southwest Senegal, the Gambia, much of Guinea-Bissau, and northwestern Guinea. The exact boundary between the two subspecies is not known.
Size, Weight, and Lifespan
Male western red colobus monkeys average 20–26 lb (9.1–12.2 kg) while females weigh between 15 and 20 lb (6.8–9.1 kg). Their size difference makes them sexually dimorphic.
They are approximately 1.4–2.1 ft (42.6–64 cm) in length with a tail that adds an additional 1.7–2.6 ft (52–79.2 cm).
The western red colobus lifespan is unknown, although there is some information about their mortality rate—in their first six months of life, they have a mortality rate of 30%. That decreases as they age (18% between 6 and 12 months), but skyrockets again to 28% between 18 and 24 months due to chimpanzee predation. Female western red colobuses have a higher mortality rate than males, likely due to the fact that they leave their natal group to travel more often than the males, who remain safe within a group.
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A western red colobus monkey looks like a formerly all-black monkey that had an irreversible, though not unfortunate, run-in with a large supply of red iron oxide powder. Their appendages and furry cheeks are rich with striking reddish-brown coat.
They have distinct T-shaped hairless faces reminiscent of everyone’s favorite extraterrestrial, E.T., and a pair of expressive almond eyes. Large, round ears protrude from the thick hair fringing their heads and their long, non-prehensile tails can often be seen hanging off of the branches beneath them.
Perhaps the most notable characteristic of the western red colobus monkey is what they lack—thumbs! A stub replaces what could have been digit number five, although the western red colobus makes up for it with long, deft fingers used for grasping—a useful feature for a creature that utilizes brachiation as a common form of locomotion.
Western red colobus monkeys are herbivorous, frugivorous, and folivorous. They prefer to snack on tender young leaves and shoots, but flowers and unripe fruits (ripe fruit contains too much sugar, which is harder for the western red colobus to digest) are also on the menu. Their complex stomachs also allow them to digest mature or even toxic foliage that other monkeys cannot—they have a ruminant-like multi-chambered stomach that is capable of digesting cellulose.
Behavior and Lifestyle
This primate is diurnal (active during daylight hours) and arboreal (tree-dwelling). They are found in all levels of the forest canopy, from close to the ground to stratum 5 (meaning the tops of developing trees greater than 130 feet (40 m) above the ground). They rarely descend to the ground, though that behavior has been recorded when they associate with Diana monkeys.
Western red colobus monkeys are incredibly agile—they move quadrupedally (on all fours) through the trees or via brachiation. Also called arm swinging, brachiation is a form of arboreal locomotion in which primates swing from tree limb to tree limb using only their arms.
Colobus is derived from the Greek word colobe, which means “cripple”—that is because they lack full thumbs.
Western red colobus monkeys are usually found in large groups of anywhere from 20 to 90 individuals. A study in Tai National Park in Cote d’Ivoire revealed an average of 53 individuals per group. They break off into smaller subgroups when foraging for food, but for the most part, the daily life of a western red colobus monkey consists of one large, noisy primate jamboree.
Females will leave their natal group and move freely between groups of males, which remain in their natal group. Males from different groups will act aggressively towards rivals as they fight for the females.
Western red colobus monkeys use vocalizations to communicate. Their repertoire consists of alarm calls that differ in duration depending on the impending threat. For instance, when chimpanzees are nearby, western red colobuses call out in alarm for a brief moment and then climb higher out of harm’s way. However, when a leopard approaches, they give a more sustained alarm call and several males will proceed to drive the leopard away.
Western red colobus monkeys also exhibit visual mimicry. Juveniles exhibit a pink genital swelling very similar to an adult female in order to avoid confrontation with older, larger, and likely stronger males of the group.
Female western red colobus monkeys have the say in which males of a group they’d prefer to mate with—they migrate from group to group until one seems satisfactory. Scientists are uncertain whether this species is monogamous or polyandrous, the former suggesting that individuals may take only one mate and the latter suggesting that females take more than one mate.
Females give birth to a single offspring every two years, but there is very little information about parental investment after birth. Western red colobus monkeys do not survive long enough to breed in captivity and few studies on this topic have been conducted in the wild. However, general observations suggest that parental involvement is limited. That being said, mothers will defend, nurse, and groom their offspring.
Western red colobus monkeys become seed dispersers during the dry season when they consume more fruits. They are also prey species for chimpanzees and leopards.
In addition, red colobus monkeys (not just the western variation) act as the proverbial “canary in the coal mine”—they are good indicators of the overall health of Africa’s forest ecosystems because of their sensitivity to habitat degradation and vulnerability to hunting (their tendency to move around in large, noisy groups makes them an easy target for poachers and bushmeat hunters).
The International Union for Conservation of Nature Red List of Threatened Species classifies the western red colobus monkey as Endangered (IUCN, 2020). The IUCN also lists their population trend as decreasing and severely fragmented.
Some of their threats include commercial and subsistence hunting—better access to forest interiors via logging roads and inconsistent law enforcement in national parks gives hunters more opportunities to poach western red colobus monkeys. They are common victims of the bushmeat trade. Habitat loss and degradation from agriculture and human activity—a lot of the western red colobus monkey’s range has become deforested as a result of logging, charcoal production, and clearance for agricultural land. Human intrusion and disturbance—war, civil unrest, and military exercises have impacted this species’ range since 1989.
Western red colobus monkeys have not been sighted for years at four forest reserves and at Marahoue National Park in Cote d’Ivoire. Their disappearance or extirpation is likely due to hunting.
A subspecies of western red colobus, P.b. waldroni, is Critically Endangered and possibly extinct (IUCN, 2016)—there have been no sightings since 1978.
The western red colobus monkey has been recorded in several protected areas in West Africa, namely the Gola Forest Reserves, Outamba-Kilimi National Park, Tiwai Island Wildlife Sanctuary (Sierra Leone), Sapo National Park (Liberia), and Tai National Park (Cote d’Ivoire).
In a new coordinated effort to conserve, recover, and protect all red colobus species, the IUCN Primate Specialist Group, the African Primatological Society and Global Wildlife Conservation (GWC) are collaborating on the Red Colobus Conservation Action Plan (ReCAP). Experts will weigh in on all red colobus forms and conservation groups of all levels—both local and international—will unite to prevent further loss of this primate and hopefully every other species that inhabit the same range.
There are approximately 5 species of red colobus and a total of 18 taxa (scientists are unfortunately unclear about exactly how many species there are) spread out across central and west Africa. Their distributed range overlaps with nearly 75% of all primate species on mainland Africa, meaning if a concerted effort is made to save the red colobus, they will become a flagship species for the many species around them that share their vanishing habitat.
Goals of ReCAP consist of developing a red colobus conservation network, improving political support, strengthening protections, improving awareness of and pride in red colobus populations, and monitoring populations (very little data exist right now).
Written by Rachel Heim, May 2019