Piliocolobus epieni

Geographic Distribution and Habitat

The Niger Delta red colobus (Piliocolobus epieni) is native to southern Nigeria. Historically, they occupied about 580 square miles (1,500 square km) of land between the Forcados-Nikrogha Creek and the Sagbama-Osiama-Agboi Creek in the Niger Delta. However, they have since experienced massive habitat and population loss, and exist only in small, isolated populations in fragmented pockets of habitat. Only about 500 individuals remain, and they are concentrated in a 77-square-mile (200 square km) area of land in the southeastern portion of their historic range. The Niger Delta region is highly unique—it is the largest river delta in Africa and supports the second largest swamp forest on the continent and the third largest contiguous mangrove forest in the world. Niger Delta red colobuses live in these marsh forests at relatively high elevations. They prefer primary, undisturbed forests, which are increasingly hard to come by in their range. Their habitat is a very carefully balanced combination of ecological features—for example, the forest grows in areas with a high water table but that do not experience deep flooding or tides. Hydrology changes from oil drilling—a massive industry in the region—have significantly altered the environment and degraded this important habitat.


​Depending upon who you ask, colobus monkeys are typically either split into two genera, Piliocolobus and Procolobus, or contained under one genus, Procolobus, with two sub-genera. This profile will follow the IUCN and consider the Niger Delta red colobus to be within the Piliocolobus genus. Niger Delta red colobuses became known to science in 1993 and were originally considered to be a subspecies of Western red colobus (Procolobus badius) and then Pennant’s red colobus (Piliocolobus pennantii). In 2008, further morphologic and mitochondrial studies suggested that they are not especially closely related to either species, and were then elevated to full species status. Some older sources still consider them a subspecies of Pennant’s red colobus.

Niger River red colobus range, IUCN 2017

Size, Weight, and Lifespan

They weigh between 15 and 24 lbs (7 and 11 kg) and have a head and body length between 21 and 24 inches (53 and 63 cm). Their tail adds another 24–28 inches (60–70 cm). Males tend to be larger than females. Based on other species in their genus, they likely live to be about 30 years of age.


Niger Delta red colobus monkeys have a strikingly beautiful coloration. Their backs are a rusty orange color, while their faces, their hands, their legs, and portions of their upper back are black. Their bellies and upper arms are white. Their heads are rather small and they have round bellies. Like many other tree-dwelling primates, they have very long arms and legs—essential for a life spent leaping from branches. Their tail is also very long and is important in helping them to navigate their arboreal environment.

Like other colobus monkeys, the Niger Delta red colobus lacks thumbs. Instead, there is only a small bump where the thumb would be. It’s not fully understood why colobus monkeys have lost their thumbs. Perhaps, given that they spend their lives moving among thick tree branches and other foliage, thumbs were more of a hindrance than an asset, and smaller—and eventually missing—thumbs became an evolutionary advantage. Their other fingers are elongated and act like hooks when swinging from branches.

This is the closely related Pennant’s red colobus, of which the Niger River red colobus was once considered a subspecies. Photo credit: ©nathanaelstanek/iNaturalist/Creative Commons

​Colobus monkeys have a unique digestive system that uses fermentation to break down very tough plant materials that aren’t available to many other animals. The downside to this is that very ripe, sugary fruit produces so much gas when it’s fermented that it can be lethal. As such, colobus monkeys, including Niger Delta red colobus monkeys, can only digest tough, unripe fruit instead of sugary, ripe fruit. They also eat plenty of young leaves and leaf buds, seeds, flowers, and flower buds.

Behavior and Lifestyle

​​Niger Delta red colobus monkeys are arboreal, living almost their entire lives in the treetops. They are quadrupedal and move gracefully throughout the trees by leaping. They can sling themselves across breaks in the canopy by vaulting from a slim branch. They spend most of their day traveling.

Fun Facts

​Niger Delta red colobuses’ scientific name, Piliocolobus epieni, comes from the word for the species in the local language, Ijaw: “epieni.

Daily Life and Group Dynamics 

Niger Delta red colobus monkeys live in groups composed of many males and females, usually with a higher proportion of females. A typical group size ranges from 15 all the way to 80 members. Females stay in their natal groups for life, while males change groups multiple times throughout their lives. They may also spend time in an all-male bachelor group. They are not territorial and intergroup dynamics are typically peaceful, though large groups may force smaller ones away from the best feeding spots. A typical home range size is 250 acres (100 ha) or more, and overlaps with other groups.


There is little information available about the communication methods of Niger Delta red colobus monkeys specifically, although there is some information available about the Pennant’s red colobus, of which the Niger Delta red colobus was once considered a subspecies. Based on that information, it is likely that Niger Delta red colobus monkeys engage in three primary social behaviors. Social presenting is a behavior in which an individual turns around and presents its rear to another individual. This is considered an act of submission, and adult males never engage in it. This sometimes leads to what’s known as social mounting—or, in some cases, actual copulation. This act mimics copulation and is considered a dominant behavior. It is performed by all, except for infants. Allogrooming is another important form of intragroup communication that helps to strengthen bonds. In terms of vocal communication, Pennant’s red colobuses have been documented emitting noises such as barks and squawks, and it is likely that Niger Delta red colobus monkeys have similar sounds in their repertoire.

Reproduction and Family

​Little is known about the reproductive lives of Niger Delta red colobus monkeys. However, we can glean some information from related species in their genus, as they likely share many commonalities. They are most likely polygynous, meaning that each male mates with multiple females. The anogenital region of a female Niger Delta red colobus swells when she is in estrus and ready to breed. To drive the point home, she presents herself to a male to indicate that she is receptive to breeding. Females give birth about every two years, and there doesn’t seem to be any seasonal pattern associated with births. Their gestation length is unknown, although it is likely between 5 and 7 months. They give birth to a single offspring. Females likely reach sexual maturity at about age 3 or 4, and males a bit later at about age 5 or 6. While we don’t know much about parenting among Niger Delta red colobus monkeys, the mother likely takes on the role as primary caregiver, at least for the first few months of the baby’s life. The baby most likely clings to her mother on her belly. After a few months of life, other group members may also play a role in child-rearing. Both male and female young resemble adult females in the genital area. This may be an adaptation to protect male babies from being harmed or pushed out from the group by adult males seeking to reduce competition.

This is the closely related Pennant’s red colobus, of which the Niger River red colobus was once considered a subspecies. Photo credit: ©nathanaelstanek/iNaturalist/Creative Commons
Ecological Role

​The main predator of Niger Delta red colobuses is crowned eagles. They share habitat with a number of other rare primates, including the red-capped mangabey (Cercocebus torquatus), the Nigerian white-throated guenon (Cercopithecus erythrogaster pococki), the putty-nosed monkey (Cercopithecus nictitans), and the mona monkey (Cercopithecus mona). Because of their unique digestive system that allows them to digest tough cellulose and unripe fruit, colobus monkeys do not tend to compete very much with other primate species in their range. Niger Delta red colobus monkeys also play an important role as seed dispersers due to the fruit they eat.

Conservation Status and Threats

According to the IUCN, the Niger Delta red colobus is considered Critically Endangered (IUCN, 2018) since its most recent assessment in 2018. This is the final step before extinction in the wild. This assessment is based on an estimated population loss of over 80% over the last three generations (about 30 years). One study estimated the population loss at closer to 90% over the last 20 years. The main threats against Niger Delta red colobus monkeys are habitat loss and degradation, largely due to logging and hydrologic changes from the oil industry, coupled with intense hunting pressure. The monkeys still live in small pockets of fragmented, degraded habitat, but the vast undisturbed swaths of habitat that they need to thrive has unfortunately been destroyed. It is believed that Niger Delta red colobus monkeys now only number in the low hundreds.

Logging in the Niger Delta red colobus range has significantly degraded their habitat, particularly by removing food trees that are extremely important to the monkeys. Over the last several decades, habitat loss and degradation has only increased in severity as the human population has grown and migrated further into the monkeys’ range. One study has found that between 1991 and 2013, forest loss in this area has occurred at an average rate of 1.2% per year. This adds up to a massive loss and a significant threat to the species over the years.

Oil extraction has also significantly degraded habitat in the Niger Delta region. There are an estimated 240,000 barrels of oil that are spilled in the delta on an annual basis. The oil spills kill trees that many animals, including Niger Delta red colobuses, rely on for survival. They also disrupt other industries, such as fishing and farming, that local people rely on for their livelihoods. The local people are often forced into hunting and logging to stay afloat, further exacerbating the environmental issue.

Conservation Efforts

Niger Delta red colobus monkeys are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES) and on Class B of the African Convention on the Conservation of Nature and Natural Resources. Unfortunately, there are no formal protected areas within the Niger Delta red colobus range. A lack of political will to conserve habitat, coupled with significant instability and unrest in the area, makes it extremely difficult to take meaningful conservation action. The government has historically not reacted kindly to people protesting the environmental degradation of the Niger Delta region. There are also armed militant groups that pose threats to conservationists, scientists, and environmental officers trying to work in the field. Logging and hunting laws are critically under-enforced, resulting in rampant deforestation, particularly of important food trees.

One organization, the Southwest Niger Delta Forest Project, is attempting to engage with local stakeholders, including authorities, hunters, bushmeat traders, and farmers, to conserve the species, although this is a difficult task considering the poverty that plagues the area. Many locals are understandably reluctant to give up logging, as it is one of the limited ways to earn a living in the region. Still, the organization is taking action. In 2020, it established a new 2,700-acre (1,000 ha) community conservancy in the Apoi Creek Forest, which will provide protected habitat to an estimated 150 to 200 Niger Delta red colobuses. The group will work with the local community to manage the conservancy.

While this new development is a step in the right direction, the decline of Niger Delta red colobus monkeys is expected to continue without immediate and significant conservation action. They are well and truly teetering on the edge of extinction.

  • Ikemeh, R. A. 2015. Assessing the Population Status of the Critically Endangered Niger Delta Red Colobus (Piliocolobus epieni). Primate Conservation 2015(29):87-96.
  • Mittermeier, R.A.,Wallis, J., Rylands, A. B., et. al. 2009. Primates in Peril: The World’s 25 Most Endangered Primates 2008–2010. Primate Conservation 24(1):1-57.​

Written by K. Clare Quinlan, January 2022