There are 536 species of monkeys in the world today and the Democratic Republic of Congo has a new one. Named Likweli, this rainforest primate is one of only five new African monkey species described in the past 75 years. Despite its distinctive orange lips, it has only been spotted by locals a few times since 2008. It took PhD student in biological sciences Junior Amboko (who named the new monkey) and an international team that included anthropologist Kate Detwiler years of searching by foot and canoe, and conducting field observations, photographs, audio recordings, genetic analysis and anatomical analysis to prove that Likweli was a species new to science. They explain their search.What is Likweli and what convinced you that this was a new species?Likweli (Colobus congoensis) is a relatively small colobus monkey, weighing about 7kg, with silky black hair and a long black tail. Like all colobus monkeys, it has no thumbs. Its most distinctive features are its face and rump. Its face is black and dark grey, framed by long, spiky black hair that continues across the forehead and onto the top of the head. The most striking feature is the pale orange-cream skin around the mouth and beneath the nose, which stands out against the dark face, especially when it makes its deep, roaring calls. At the base of the tail is a bright white patch.We became convinced that Likweli was a new species of monkey because our genetic analyses showed that the ancestor of Likweli split from the ancestor of Colobus satanas, another similar species found today in the region, about four to five million years ago. This was much further back than we expected and provided strong evidence that Likweli is a distinct species.What’s more, the two species are separated by more than 1,200km and several major rivers. This raises questions about how the Congo Basin’s river system has shaped the evolution and distribution of mammals over millions of years.Why did it take so long to confirm that Likweli existed?Likweli lives in one of the most remote parts of the DRC, in a small area of about 1,700km². It is rare, shy and usually stays high in the forest canopy. It has rarely been seen, even by communities who lived next to its habitat We had to visit 52 villages and speak to local residents and hunters to find out where the monkey lived and how it behaved. We asked them to describe the animals they had seen, what they called them, where they had spotted them, and whether they hunted them. If community members described a monkey that looked like Likweli, which had been seen from time to time by locals for generations, we asked them to guide us to the place where it had been spotted. Read more: Red colobus are Africa’s most endangered monkeys – protecting them will also safeguard forests It took some time to reach these sites because the forest where Likweli lives can’t be reached by a tar road. Reaching Likweli’s forest home means taking a flight, a motorcycle ride, two days of hiking and finally a dugout canoe. These difficulties help explain why the region remains so little explored and why Likweli escaped scientific recognition for so long. We also needed to bring in researchers with expertise in ecology, anatomy, genetics and the monkey’s calls. We had to record the monkey’s distinctive roaring calls at six locations in Lomami National Park and compare them with calls from closely related colobus monkeys to make sure they were different. Read more: Wild animals leave DNA on plants, making them easier to track – here’s what scientists found in a Ugandan rainforest It took even more time for us to analyse the recordings to see whether the Likweli’s calls were unique enough to support it being recognised as a separate species.Getting biological samples out of the DRC for analysis also required lengthy paperwork. All of this work meant it was a long time before we could confirm Likweli as a new species.What is the discovery of Likweli so important?Like other colobus monkeys, Likweli is an important part of the Congo rainforest ecosystem. We have not yet studied what Likweli eats, but colobus monkeys generally feed on leaves, flowers and fruits. By eating and spreading seeds, they help new plants grow and shape the forest around them. In this way, Likweli contributes to the natural balance of the rainforest. We still have much to learn about the Likweli monkey specifically. Protecting it also helps protect the entire forest and the many other species that share its habitat.What have you learned about the monkey’s behaviour and what questions do you still have?Our research is really just beginning, so we don’t know much about Likweli’s behaviour yet. We did observe though that it’s usually found in mixed groups with other monkey species. What is special about Likweli is that it seldom flees from humans. Instead, the monkeys climb high into the canopy and watch the humans who are watching them. We sometimes stood for over one hour observing each other.This is unusual because other sympatric species (animals that share the same habitat with other species) generally do flee. Read more: Africa’s rainforests are different. Why it matters that they’re protected We want to understand every aspect of Likweli’s natural history. We want to find out what it eats, how it behaves, how it moves through the forest, how it uses different levels of the forest canopy and how far it travels each day. We also want to know how it reproduces, how large its population is, how males and females differ, and how vulnerable it is to hunting and environmental change, including climate change. Every new finding will bring us closer to understanding and protecting Likweli.Will official recognition protect Likweli from hunting and habitat loss?Discovering a new species matters because you can’t effectively conserve what you don’t know exists. Once a species is formally recognised, we can study how it lives, assess how threatened it is, understand the dangers it faces and work out how to protect it. Formal recognition of the species also helps attract scientific attention and conservation funding. Read more: Protecting Congo’s forests: new timber parks will help fight illegal logging Our study shows that the Likweli monkey occurs in low numbers, and appears to only live in a small area of DRC rainforest. This means we now know it may be particularly vulnerable to threats such as hunting and habitat loss. The Lomami National Park management team will use that information to strengthen protection efforts, including targeted patrols within the species’ known range.Junior Amboko receives funding from National Geographic Society. Kate Detwiler receives funding from Primatology Lab, FAU Foundation, Inc.