Orange-lipped monkey confirmed as new species in DR Congo, only the fifth African primate discovery in 75 years

The search

A blurry photograph taken in 2008 first hinted at an unusual monkey high in the canopy of what is now Lomami National Park. The image showed only the animal's back, and no one followed up. A second sighting a decade later, with much clearer photos, revealed a medium-sized black monkey with a pinkish-orange mouth and mask-like grey cheeks. "We were able to tell that it was something unusual," said Junior Amboko, a PhD student at Florida Atlantic University who later led the study.

In 2020, an international team launched a dedicated project to track down the primate. Over four years they covered more than 3,000 miles on foot patrols, recorded calls at dawn, interviewed residents of 52 villages, and collected 114 field observations. Only people in eight villages had ever seen the monkey; those from the Balanga ethnic group called it Likweli.

Probably not many people who would be interested in discovering monkeys and things had ever gone there.

Physical traits

Colobus congoensis has glossy black fur, a long black tail, and a conspicuous white patch at the base of the tail. Its face is dark grey with bare grey skin on the cheeks and a black mask around the eyes. The most striking feature is the vivid orange skin around the nose and mouth, which contrasts sharply with the rest of the face. Adults weigh about 15 pounds and reach roughly four feet from nose to tail, smaller than related colobus monkeys.

The animal belongs to the colobus genus, confirmed by its tiny thumbs. Colobus monkeys lack fully developed thumbs, a trait that gives the group its name, derived from the Greek for "mutilated".

Behavior and habitat

The monkeys live in a narrow patch of closed-canopy forest between the Lomami and Lilo rivers, an area of at least 1,700 square kilometres roughly half the size of Rhode Island. They are shy and seldom descend from the high treetops. "You often hear them, but don't see them," Amboko said. Their low, roaring call punctuated by snorts carries through the forest, yet the primates themselves remain hidden.

They're kind of shy.

Researchers believe the orange facial markings may serve as a visual signal, helping individuals recognise one another or attract mates. Prof Kate Detwiler of Florida Atlantic University, the study's senior author, noted that the animal's role as a canopy herbivore makes it important for seed dispersal and forest regeneration.

Conservation

Because Colobus congoensis occupies such a small range and only a limited number of sightings exist, the authors recommend it be classified as Endangered on the IUCN Red List. The main threats are habitat loss and hunting pressure. In 2021, specimens confiscated from hunters inside the national park provided the tissue that unlocked the genetic evidence.

What it reveals

The DNA analysis showed the new species split from its closest relative, the black colobus (Colobus satanas), between 4.3 million and 5.8 million years ago, one of the oldest divergences in the colobus lineage. "When we got the genetics and we shared it with the team, we were like, 'Oh my gosh, it has such a deep divergence,'" Detwiler said. The two species are now separated by more than 1,200 kilometres, occupying entirely different forest blocks.

They're these herbivores of the canopy that are a critical part of the ecosystem. We think they have a lot to do with processing seeds and germination in the forest.

The discovery, published in the journal PLOS One, underscores how little is still known about the Congo Basin's biodiversity. It is only the fifth African monkey species described in the past 75 years and the second new species found around the Lomami River in the last 15 years.