Western Red Colobus, Piliocolobus badius
WESTERN RED COLOBUS
Piliocolobus badius
Geographic Distribution and Habitat
You’ll find the western red colobus (Piliocolobus badius) monkey—also known as the bay red colobus, rust red colobus, and Upper Guinea red colobus—in the tropical rainforests of coastal West Africa. The species’ geographic distribution ranges from southwestern Senegal and the Gambia, south and east to the Nzi-Bandama River system in western Côte d’Ivoire (the Ivory Coast), while encompassing fragmented populations within Sierra Leone and contiguous populations within the countries of Liberia, Guinea, and Guinea-Bissau.
Moist, lowland forests provide the species with its habitat. These monkeys are found from ground level to trees as high as 131 feet (40 m). Most often, however, they reside in the higher canopy at elevations of 66 to 98 feet (20–30 m). Primary old growth forests are preferred, but western red colobus also inhabit secondary, gallery, and mangrove forests, along with woodland savanna, tree and shrub savanna, and residential gardens.
The western red colobus is thought to be one of 18 distinct forms of red colobus monkeys, though scientists are reticent to declare a definitive number of species. Of these 18, over half are classified as Endangered or Critically Endangered on the IUCN Red List of Threatened Species.
Current taxonomic opinion is divided, with some scientists asserting that red colobus monkeys and the olive colobus monkey (Procolobus verus), also known as the green colobus, belong to two separate genera (Piliocolobus and Procolobus); meanwhile, other scientists assert that the olive and red colobus monkeys belong to one genus, Procolobus, with two subgenera: Procolobus for the olive colobus and Piliocolobus for the red colobus.
This primate species profile follows the lead of the IUCN classification regarding the western red colobus as distinct species within its own genus, Piliocolobus, with subspecies; and the olive colobus as a distinct species within its own genus, Procolobus, with no as-yet-defined subspecies.
If your head isn’t in a taxonomic swirl yet . . .
At one time, all red colobus monkeys were considered to be subspecies of Piliocolobus badius. Today, just three subspecies are identified as “children” of the western red colobus. Introducing:
- The bay colobus (Piliocolobus badius badius, the nominate subspecies), found in fragmented populations within Sierra Leone, southern Guinea, Liberia, and western Côte d’Ivoire.
- Temminck’s red colobus (b. Temminckii), found in southwestern Senegal, the Gambia, much of Guinea-Bissau, and northwestern Guinea.
- Miss Waldron’s red colobus (b. Waldroni), might still be found in forestland between the Ehy Lagoon and Tanoe River of western Ghana. Decades-old evidence has allowed some wildlife biologists to express cautious optimism of this subspecies’ continued existence. But a grave possibility exists that this subspecies may be extinct. Current studies—and sightings—are necessary to confirm that Miss Waldron has not been ushered out of the world we share.
Size, Weight, and Lifespan
Head-to-body length for adult males is between 19.7 and 25 inches (50–63 cm) and between 17 and 25 inches (43–63 cm) for females. A long, nonprehensile tail adds another 25 to 30 inches (63–77 cm) to the body of both sexes. Males carry a bit more girth on their frames than females, weighing between 20 and 27 pounds (9.1–12.2 kg); females weigh between 15 and 20 pounds (6.8–9.1 kg). Not all populations exhibit this sexual dimorphism, however. As example, both male and female western colobus monkeys of Sierra Leone are the same size.
While lifespan for western red colobus monkeys is unknown, scientists have identified several factors known to impact the species’ mortality. Not surprisingly, infants are the most vulnerable with a mortality rate of 30 percent from birth to 6 months of age. Mortality rate decreases to 18 percent between 6 and 12 months of age but surges to 28 percent between 18 and 24 months of age—a direct result of chimpanzee predation. Females experience a higher mortality rate when compared to males. Because they often migrate between groups, females expose themselves to dangers, including predator threats. In contrast, males typically stay put within the safety of their group.
Other colobus species are reported to have a lifespan of about 20 years in the wild.
Appearance
Let’s first talk about that face. While some see a strong resemblance to the loveable alien E.T. of Hollywood fame (and we won’t deny the likeness), we prefer to liken this monkey’s hairless, wizened visage to that of the legendary vampire Nosferatu—except with dark pigmentation, save pale pink skin beneath almond-shaped brown eyes and surrounding the narrow lips. A pug nose with generous nostrils completes the facial features.
Flaring out from either side of this monkey’s arresting face are long tufts of reddish-orange fur. A few of these colorful, errant strands add highlights to a dark furry crown, while punk-rock spikes of black fur edge the hairline. Scalloped ears sit tucked on either side of the head. This colobus monkey’s signature reddish-orange fur luxuriantly garnishes his limbs and belly, giving dramatic contrast to a black or silvery colored coat that cloaks the back. The long tail is mostly furred in red with darker fur encroaching toward the tip. The pubic area and inner hind quarters are demurely covered by white fur.
Subtle color variations in pelage (fur coat) occur across the species’ range and even within a single population. Likewise, each of the three subspecies is distinguished by slight variations in pelage and overall appearance.
Mother Nature decided against giving thumbs to these primates, leaving only a small stump where these digits should be. No matter. She thoughtfully fitted western red colobus monkeys with long, dexterous fingers that can easily grasp branches as the monkeys fluidly move through the forest. Thumbs would only be in the way as they swing from branch to branch. The big toe on each foot is short.
Diet
Young leaves, mature leaves, unripe fruits, seeds, shoots, and flowers comprise the diet of these folivorous/frugivorous herbivores (they eat lots of leaves and fruits in their plant-based diet). Ripened fruits are avoided, as they tend to cause gas and stomach upset.
Food sources include the following:
- Velvet Tamarind (Dialium guineense)
- African Locust-Bean (Parkia bicolor)
- African Nutmeg (Pycnanthus angolensis)
- Boleko Nut (Ongokea gore)
- Persimmons (Diospyros)
- Raphia Palm (Raphia africana)
These colobus monkeys are also known to eat charcoal or clay to help neutralize the cyanide contained in certain leaves. A multichambered stomach (similar to that of cows) helps to digest leaf cellulose.
Behavior and Lifestyle
These are arboreal primates (spending their lives in the trees), rarely descending to the forest floor. The only time they are known to descend to the ground is when traveling with Diana monkeys (Cercopithecus diana). Western red colobus monkeys are active during daylight hours, making them diurnal. To efficiently travel through their treed environment, these highly agile monkeys use a form of arboreal locomotion known as “brachiation.” They advance by swinging from tree limb to tree limb using their strong arms to support their weight as their long, nimble fingers grasp purchase. While their tail is incapable of grasping, it acts as a rudder and provides balance as the monkeys maneuver. They might also leap from tree to tree or run quadrupedally, using all four limbs.
Western red colobus monkeys spend their days foraging, feeding, grooming, playing—and resting. Pads on their bottoms, known as ischial callosities, enable these monkeys to sit comfortably on tree branches for long periods of time. (Ischial relates to the ischium, the curved bone at the base of the pelvis that forms the lower and back part of the hip bone; callosities refer to the hardened skin that encloses these comfy pads.) Because they tend to rest a lot when their bellies are full, these colobus monkeys are easy prey to predators who include chimpanzees (Pan troglodytes), leopards (Panthera pardus), crowned hawk-eagles (Stephanoaetus coronatus), and humans (Homo sapiens). Fortunately, western red colobus monkeys’ association with Diana monkeys is beneficial to both species, enhancing their ability to detect and evade common predators. Overnight, colobus monkeys typically sleep in the same trees where they feed.
The name “colobus” is derived from the Greek word for “mutilated” and refers to the species’ lack of thumbs.
Group size ranges from 20 to 90 members and includes both males and females, young and old. A study conducted in Taï National Park in Côte d’Ivoire, reported in 2007, revealed the average group size to be 53 individuals for that population. An earlier study at Abuko Nature Reserve in Gambia revealed average group size to be 26 individuals.
Within a group (also known as a “troop”), females largely outnumber males. A social hierarchy exists, ensuring that more dominant individuals enjoy such perks as preferential access to food, personal space, and being the privileged recipients of grooming. Showing no favoritism, females groom both other females and males of their group equally—though they appear to favor the company of males, generally. Males, themselves, tend to groom infrequently.
A group’s home range is between 123 and 161 acres (50–65 hectares), often overlapping with that of the three subspecies. The species is highly territorial. Upon reaching sexual maturity, females leave their natal (birth) group and move freely between other groups. Males are homebodies and usually remain with their natal group.
Besides Diana monkeys, other colobus monkeys, and chimpanzees . . . other wildlife species found throughout the geographic range of the western red colobus include: elephants, lions, baboons, hyenas, warthogs, gazelles, antelopes, wild dogs, and servals (wild cats). All these species, like the western red colobus monkey, face an uncertain future due to habitat loss and other anthropogenic (human-caused) hazardous activities.
Western red colobus monkeys draw from a repertoire of vocalizations to communicate. Alarm calls are particularly important in alerting group members to a predator. These calls vary in duration, depending on the type of predator and the impending threat. As example, upon detecting a chimpanzee, group members emit a quick alarm call before retreating to safety high into the trees, up to 85 ft (26 m). If the predator threat is a leopard, group members emit an extended alarm call and then several of the group’s males attempt to chase away the big cat.
As a tactile communication activity, mutual grooming sessions help to foster social bonds with one another.
Visual communication cues are not what they seem. Juveniles rely on deceptive visual mimicry (a visual fake-out that is natural and biological) to avoid confrontations with older, dominant males. Because these youngsters—both males and females—display pink genital swellings similar to (or mimicking) that of ovulating females, the older males are duped into not bothering the juveniles. At this younger age, the penis and scrotum are not yet obvious, further lessening the chances of harassment from older, bullying males. As individuals reach maturity, this genital swelling subsides in both sexes (swelling again only in ovulating females), and the pinkish genital coloring in males changes dramatically to a grayish-yellowish-red color.
Wildlife biologists are uncertain whether the species’ mating system is polyandrous (females have multiple male sexual partners) or monogamous (a male and female are exclusive partners). But it appears that females get to choose their mating partner; if no male catches her fancy in one group, a female simply moves to another group to find a male to her liking.
When a female is ovulating, her genitals become swollen and pink—a biological indicator that she is ready to mate. Males, aware that a female selectively chooses her mating partner and may seek one outside her group, may engage in aggression with one another as they vie for her attention.
Female colobus monkeys reach sexual maturity (ability to conceive and bear young) at about 4 years of age; males reach sexual maturity (able to sire young) at about 5 or 6 years of age. Breeding for western red colobus monkeys occurs throughout the year, though a peak in births occurs during the rainy season when new leaves provide an abundant food source.
Following a gestation period of 6 to 6.5 months, a single infant is born. Interbirth interval for the species is 24 months. Mothers nurse, groom, and protect their offspring. Beyond this initial care, little information is available about parental investment.
Thanks to their dietary proclivities, western red colobus monkeys help to regenerate their forested ecosystem by dispersing seeds, via their feces, throughout their environment.
With most of the species facing extinction, red colobus monkeys are the most threatened group of non-ape primates in mainland Africa.
Western red colobus monkeys are classified as Endangered by the International Union for Conservation of Nature (IUCN, January 2020), appearing on the IUCN Red List of Threatened Species. Total population size is unknown, though drastic population declines and even extirpation (total expulsion) in some areas have been reported through recent surveys.
Habitat loss and hunting are primarily responsible for the species’ decline. Large tracts of forest have been—and continue to be—razed through logging, charcoal production, and mining, and for transformation into agricultural land, plantations, and human settlements. Both subsistence hunting by locals and commercial hunting (the monkeys are killed and eaten for their flesh, known as “bushmeat”) have taken a devastating toll on the population. The monkeys are also killed and skinned for their fur. With the increase in logging roads, hunters have easier access to their prey.
Red colobus monkeys are especially sensitive to disturbances in their environment: stress kills them. Thus, civil war and political unrest throughout the western red colobus distribution has negatively impacted the species’ population, though the extent is unknown. Because the monkeys do not reproduce when their habitat is destroyed, they are driven to stress-extinction.
The three subspecies are also threatened with extinction: both the bay colobus and Temminck’s red colobus are classified by the IUCN as Endangered; Ms. Waldron’s is classified Critically Endangered and she may already be extinct. Even if a handful of individuals exist, a few does not constitute a viable population, according to wildlife biologists; the monkeys would not be able to reproduce; thus, they would be considered functionally extinct.
Western red colobus monkeys 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. The species is also listed as Class B in the African Convention on the Conservation of Nature and Natural Resources.
Protected areas include the Tai Forest National Park in Ivory Coast; Sapo National Park in Liberia; and Outamba-Kilimi National Park, Gola Forest Reserve, and Tiwai Island Wildlife Sanctuary in Sierra Leone. Of course, these protections mean nothing if they are not enforced.
Protection laws are routinely flouted by poachers.
A 2012 paper published in the scientific journal Conservation Letters identifies red colobus monkeys as a “Cinderella species—a species that is currently overlooked, but aesthetically appealing.” Wildlife biologists hope that this attention may help save the species and many other wildlife species who share red colobus habitat.
The Red Colobus Conservation Action Plan (ReCAP) was implemented in 2018, formed under the auspices of the African Primatological Society and IUCN-SSC (Species Survival Commission) Primate Specialist Group and the Red Colobus Conservation Network. ReCAP has put forward specific, ambitious goals: to expand and strengthen conservation for the genus Piliocolobus; to raise awareness for all red colobus monkeys and their dwindling habitats; to increase political support and support of conservation efforts from countries in the species’ range; to build research and conservation capacity through training and mentoring; and to develop continent-wide initiatives that link activities. Included in these activities are outreach and community education programs that cultivate local pride for the many red colobus species; anti-poaching initiatives that use monitoring technology; population surveys; and genetic studies of the various species. All these efforts are intended to support the next generation of conservationists.
Effective conservation of the genus Piliocolobus helps to protect many other wildlife species, including the roughly three-quarters of all African primates whose ranges overlap that of red colobus monkeys.
The conservation group Re:wild, launched in 2021 and founded by Hollywood film star/environmental activist Leonardo DiCaprio, in unison with Global Wildlife Conservation, embraces a mission to “protect and restore the wild to build a thriving Earth where all life flourishes.” Re:wild boasts over 200 active project sites in more than 80 countries, leading direct conservation action for over 160 threatened species while leveraging support for an additional 30,000 species.
Actively working with ReCAP conservation partners, Re:wild is committed to shining a spotlight on red colobus monkeys and supports expeditions to find “lost species.” Re:wild’s hope is that a collaborative effort will elevate red colobus monkeys, including the western red colobus, to a flagship species to serve as an ambassador for the conservation and protection of their environment—and save these primates from extinction.
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Written by Kathleen Downey, May 1, 2023