Piliocolobus parmentieri

Geographic Distribution and Habitat

The Lomami red colobus (Piliocolobus parmentieri), also known as the Lomami River red colobus, is endemic to the Democratic Republic of the Congo, deep in the rainforests of the Congo Basin. A species is “endemic” to a place when it is found nowhere else in the world. The historic range of the monkeys covered roughly 7,200 square miles (19,000 square km). Today, largely due to conversion of forest to agricultural land, they inhabit just over half of their historic range, an area of about 3,800 square miles (10,000 square km). They have even disappeared from what was once considered their stronghold, the Lobaye River basin. They seem to favor primary forest — that is, forest that has not been substantially altered in at least the last few centuries (and oftentimes much longer than that—even thousands of years). They do not seem to spend time in young forest that has grown back following clear-cutting. They are believed to live in highly fragmented and isolated population groups. As is sadly the case for many endangered primates, Lomami red colobuses are severely under-studied. There have been no field studies focused on them, so their ecology and behavior are largely a mystery, and can only be inferred from what we know of related species.


The taxonomic arrangement of the red colobus monkeys has long been disputed. Red colobus monkeys are sometimes considered to be their own genus, Piliocolobus, or are sometimes lumped in with the olive colobus monkeys under the genus Procolobus. This profile follows the classification of the International Union for Conservation of Nature, which adheres to the former. In the past, Lomami red colobuses have been considered subspecies of Oustalet’s red colobus (P. oustaleti), Foa’s red colobus (P. foai), and Pennant’s red colobus (P. pennantii). However, they are now commonly considered to be their own species, joining 16 other species of red colobus in the most widely accepted classification.

Lomami red colobus range, IUCN 2023

Size, Weight, and Lifespan

Lomami red colobuses weigh between 15 to 24 pounds (7-11 kg), with males on the heavier side. Their head and body ranges in length from 21 to 25 inches (53-63 cm), and their tail ranges from 24 to 28 inches (60-70 cm). Based on related species, they likely live to an age of about 25 to 30 years.


Lomami red colobuses, as their name implies, are a beautiful rusty red color over most of their body. They are distinguished from other red colobuses by their black “cape” that covers their shoulders and upper back, their white undersides, and black hands and feet. Their upper lip is also white, another feature that helps in identification.

Like other colobus monkeys, Lomami red colobus monkeys appear to lack thumbs, with only small bumps where you’d expect them to be — a surprising characteristic for a primate. In fact, the word “colobus” is derived from the Greek word “kolobus”, meaning “mutilated” or “truncated”, as they appear to have had their thumbs cut off. X-rays of colobus hands reveal that they do have a thumb bone, it’s just very small and mostly hidden within the hand. The evolutionary explanation for why these monkeys lost their thumbs isn’t known for certain, but it may have to do with their thumbs getting in the way as they speed through the canopy. Over time, monkeys with long, slim hands and small thumbs were better able to navigate the forests and survive to pass on their genes.

Photo: © Paul Falay/iNaturalist/Creative Commons

Lomami red colobuses are primarily folivorous, meaning that their diet is leaf-heavy. In addition to young leaves and shoots, they also consume fruits and seeds, and even fungi and clay. They can’t eat fruit that is too ripe, as colobuses have special complex stomachs that are capable of fermenting food. If they consume food that is too sugary, such as ripened fruit, their stomachs can fill with excess gas and acid as they digest. This can be painful and even lead to death. So Lomami red colobuses stick with unripe fruit. This allows them to access foods that would be difficult or impossible for other species to digest, reducing competition for food.

Behavior and Lifestyle

Lomami red colobuses are arboreal, meaning they spend nearly all their time in trees. They forage, eat, socialize, and even sleep in the trees, descending to the ground only rarely. A major advantage of this lifestyle is safety, as they don’t need to worry about predators on the ground. Lomami red colobuses are also diurnal, meaning that they are awake during the day and sleep at night. They move about quadrupedally — on all fours, walking on branches and leaping from tree to tree. They move very agilely, even elegantly, effortlessly navigating dense canopy from the time they are only months old. Unfortunately, very little else is known about their behavior due to a lack of field studies.

Fun Facts

Colobuses have special complex stomachs that are capable of fermenting food. Ripe fruit can cause gastrointestinal pain and, in extreme cases, even death, as the sugars within them ferment in the stomach. The upside to this unique digestive system is that colobus monkeys can consume foods that other primates can’t easily digest, like mature leaves and unripe fruit.

Lomami red colobuses are considered a “surrogate” or “indicator” species — species which, when they have an abundant population, indicates a healthy ecosystem. Prioritizing the conservation of surrogate species can improve the health of the overall ecosystem. Surrogate species can be used to increase support for the conservation of an overall ecosystem. When Lomami red colobuses do well, so do the many species that share their habitat.

Daily Life and Group Dynamics

Lomami red colobuses live in large groups of multiple males and females, usually with a higher proportion of females. Females stay in the group they were born into, their natal group, for life, while males usually join multiple groups throughout their lifetime. Occasionally, stray males form loose, all-male bachelor groups. Relations between groups are usually peaceful, though occasionally a group may force another out of a prime feeding location. There is a dominance hierarchy within the group, though it is not well understood. Higher-ranking males tend to perform dominant behaviors, while lower-ranking members, including females and young males, tend to perform submissive behaviors.


Red colobuses employ a number of communication tactics. Social communication is particularly important and can include behaviors like allogrooming and social presenting. Allogrooming is the act of grooming a groupmate, picking them free of parasites, dead skin, and other debris. It is important not only for health and hygiene but as a form of bonding. Social presenting is a behavior in which a colobus presents his or her rear towards a groupmate and bows their upper half low. It is done by adult females and young of both sexes. This is sometimes followed by social mounting — an act that looks a lot like copulation but is used to enforce dominance hierarchies. All members of the group, except for infants, engage in social mounting. Vocal communication is also important and includes noises like barks and squawks.

Reproduction and Family

Reproduction among Lomami red colobuses is unfortunately not well understood, but the basics can be gleaned from other red colobuses, who likely all share similar traits in this regard. Females exhibit a swelling of their genital region when they are in estrus and receptive to breeding. They use social presenting to indicate their readiness to mate. Pregnant females often separate themselves from the group before birth, returning only after the baby is born. Their gestation time is unknown, but it is likely around five to seven months. Once their baby is born, the mother is the sole caregiver for the first few months. After this point, other members of the group may help to care for the baby, a behavior known as alloparenting. Babies cling to their mothers until they are about eight months old, after which they begin to have more independence, moving about on their own. Upon reaching maturity, male offspring leave the group to find their own, and female offspring remain with the group.

Photo: © Paul Falay/iNaturalist/Creative Commons
Ecological Role

Lomami red colobuses act as predators to the plants that they eat, and are themselves prey to the predators that live in their habitat, such as birds of prey. Red colobuses are extremely ecologically important and are considered a “surrogate” or “indicator” species — species which, when they have an abundant population, indicate a healthy ecosystem. On the flip side, when red colobus populations are struggling, this is an indication that an ecosystem is not doing well. Prioritizing the conservation of surrogate species can improve the health of the overall ecosystem.

Conservation Status and Threats

The International Union for Conservation of Nature lists the Lomami red colobus as Endangered (IUCN, 2017) appearing on the IUCN’s Red List of Threatened Species. This assessment is based on a predicted population loss of more than 50% over the next 30 years. It is believed there are less than 2,500 Lomami red colobuses remaining today. The main threats to Lomami red colobuses include rampant habitat loss and unregulated hunting.

The rate of forest loss in the Lomami River region was reported to have quadrupled since the turn of the century and has continued to accelerate since then. Models predict a loss of 20% or more of forest cover in the Lomami red colobus’s range between 2009 and 2038. The major reason for deforestation is clear-cutting in order to make room for agricultural fields. Lomami red colobuses are also a favorite target for bushmeat hunters. Data from market surveys suggests that the hunting of the monkeys for food will not reduce in popularity anytime soon. They are a prime target for hunters because they are relatively large-bodied, and they are rather curious towards humans, displaying interest instead of fear at the predators. They also form large, noisy groups, so they are not difficult for hunters to find. Without strict regulation, the colobuses will continue to be overhunted wherever they live.

Conservation Efforts

Lomami red colobuses 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. They are also listed on Class B of the African Convention on the Conservation of Nature and Natural Resources, a landmark continent-wide agreement enacted to protect Africa’s diverse natural resources. Animals in Class B are protected and can only be hunted or captured under special authorization. Lomami red colobuses are also protected federally under the Democratic Republic of the Congo’s Ministry of the Environment. Sadly, despite having international and federal protection, Lomami red colobuses are still over-hunted and are being driven to extinction.

There are five main priority areas for conservation action as identified by scientists: 1) Increasing legal protections, and enforcement of current laws, 2) Carrying out field studies and surveys of Lomami red colobuses to learn more about their behavior and ecology and more clearly define their range, 3) Creating more protected areas and improving their management, 4) Supporting and engaging people who live near the red colobuses, and 5) Investing in conservation education.

Lomami red colobus habitat is protected by the Lomami National Park, which was created in 2016. Satellite data shows that very little deforestation has occurred within the park since then, though it is not without controversy. The park has faced accusations of improper displacement of local villages, failure to include locals in decision-making processes that impact their lives, and heavy-handed military enforcement. While it is undoubtedly important to protect habitat, some conservationists argue that more should be done to promote the monkeys living in harmony near people, and not simply creating areas free of human settlements. This, they argue, would improve outcomes for both people and monkeys.

Because of their ecological importance as surrogate species, scientists predict that bolstering red colobus populations will likely have a ripple effect, improving the overall health of the ecosystems in which they live. Surrogate species also often make effective flagship species — these are those that can be used as a sort of rallying point to improve public awareness, secure funding, and increase support for the conservation of an overall ecosystem. In other words, when people promote red colobus conservation, they are also, often unknowingly, promoting the conservation of millions of plants, amphibians, insects, reptiles, and other species that don’t often get public support.

  • https://www.iucnredlist.org/species/40648/166604269
  • https://www.downtoearth.org.in/news/africa/red-colobus-conserving-these-old-world-primates-could-help-save-africa-s-tropical-forests-says-study-95900
  • https://newsroom.wcs.org/News-Releases/articleType/ArticleView/articleId/22406/A-Rare-and-Little-Known-Group-of-Monkeys-Could-Help-Save-Africas-Tropical-Forests.aspx
  • https://conbio.onlinelibrary.wiley.com/doi/10.1111/conl.13014
  • https://www.nps.gov/articles/surrogate-species-piecing-together-the-whole-picture.htm
  • https://www.bonoboincongo.com/2017/06/12/two-red-colobus-two-sides-of-the-lomami-river/
  • https://animaldiversity.org/accounts/Piliocolobus_pennantii/
  • https://portals.iucn.org/library/sites/library/files/documents/2021-015-En.pdf
  • https://news.mongabay.com/2019/10/bonobo-conservation-stymied-by-deforestation-human-rights-abuses/

Written by K. Clare Quinlan, June 2024