Scientists have identified a new species of monkey that has orange lips and makes unique roars and snorting sounds. The distinctive monkey lives in a remote region of the Democratic Republic of the Congo (DRC).

It is only the fifth new monkey species to be identified in Africa in the past 75 years, and there might be more unknown monkey species in the region, scientists behind a new study suggested. Researchers named the newly identified species of monkey Colobus congoensis, after the region, and it is known by the common name "lik­weli" in the local Kilanga language.

"This is remarkable because it's not very common these days to find a new, never-before-documented primate species, let alone a relatively large species of monkey," said Joshua Linder, an anthropologist and president and co-founder of the The Forest Collective, a nonprofit that aims to conserve and restore tropical rainforests.

In 2008, conservationists in the dense rainforests of Lomami National Park, within the Congo Basin in the DRC, photographed an unidentified monkey, but it was partially obscured. Then, in 2018 a similar-looking animal was captured on camera, prompting study co-author Junior Amboko, a Lomami National Park researcher and a Florida Atlantic University anthropologist, to set out to find the mysterious monkey.

To see what was already known, Amboko and his colleagues showed the pictures to people from 52 villages around the park.

"These people really know the fauna and flora in the forest," Amboko told Live Science. "In only eight villages, people knew the monkey ‪—‬ and these were hunters, who know the economic value of animals or how much food each animal can provide, but even they didn't know much."

Hunters of the Balanga ethnic group called the monkey "likweli," although the meaning of this name isn't known. Some in the Mituku local communities called the species "kasaba nkoni," which Amboko said means "the branch shaker." This refers to the way colobus monkeys leap from branch to branch, Amboko said.

In their searches between 2018 and 2022, the researchers recorded 114 sightings of the species across an estimated range of about 660 square miles (1,700 square kilometers) naturally isolated between the Lomami and Lualaba rivers. They reported their findings July 15 in the journal PLOS One.

The monkeys, seen hanging out in groups of between one and 20 individuals, are mainly glossy black, but they have a conspicuous orange patch around the mouth and nose. Bare gray skin on their cheekbones makes it look as if they're wearing masks. They also have a patch of white fur around the anus.

"We're going with the face and the rump as the two distinctive traits," said study co-author Kate Detwiler, an anthropologist at Florida Atlantic University. "If you see the face, you see this unique bare skin that's orange cream. And then if you're coming from behind, you see this white patch."

The monkeys, which weigh about 15 pounds (7 kilograms), also make deep, loud roars, punctuated by distinctive snorts. These unique‬ vocalizations distinguish them from other colobus monkeys, Detwiler told Live Science.

By taking samples, and sequencing DNA, from monkeys killed by hunters and destined for the illegal bushmeat trade, and comparing the results with what’s in museum collections and datasets of genetics, skulls, teeth and pelts for other colobus monkeys, the team confirmed that C. congoensis was a previously unknown species.

"My lab got the tissue sample and did the genetics, and we were shocked by how divergent the key area of the mitochondrial genome was from other colobus monkeys," Detwiler said.

The monkeys live in the same forest as the Angola colobus (Colobus angolensis), but their closest relatives are black colobus monkeys (Colobus satanas), which live around 750 miles (1,200 kilometers) to the west, in Cameroon, Gabon and Bioko Island.

"The fact that the results show that the closest living relative to this new species is the black colobus located 1200 km away in West Africa is equally remarkable," Linder, who was not involved in the new study, told Live Science via email.

Detwiler estimates that these close relatives diverged between 5.78 million and 3.44 million years ago ‪—‬ the longest known split between species within the Colobus genus. "The discovery is reshaping our understanding of African monkey evolution," she said.

Given the small geographic range, rare sightings and increasing habitat loss, the researchers recommend that C. congoensis be classified as endangered on the IUCN Red List.

The discovery also emphasizes the importance of Lomami National Park, where another previously undescribed monkey, the lesula (Cercopithecus lomamiensis), was reported in 2012 by a team that included Detwiler.

The Congolian rainforest ranging across this part of Africa is the world's second-largest tropical forest, after the Amazon, and about 60% of it is in the DRC. "It is a paradise for biodiversity," Amboko said, adding that there might be more undescribed primate species there. "If we are able to discover two big new primate species, who knows how many other new mammals, fish, reptiles or plants there could be?"

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