How scientists tracked down a new monkey species in the Congo rainforest

Deep in the Congolese rainforest, scientists have discovered a new species of monkey so elusive even local communities knew little of its existence.

Dubbed “Likweli,” it sports a black coat, a pink and orange mouth and a low, roaring call. Scientists estimate the monkeys weigh about 15 pounds, similar to a small dog, and span around four feet in length from nose to tail.

To find the monkeys, researchers did periodic patrols over several years that together traversed more than 3,000 miles n a remote and thickly forested part of the Democratic Republic of Congo. The discovery, published Wednesday in the peer-reviewed journal PLOS One, marks the second species discovered in the past 15 years around the Lomami River, which runs down the country’s center.

The first sighting of Likweli monkeys came in 2008 on a research expedition down the waterway, which ended up in an isolated portion of the forest nestled in between two bends of the river.

“Probably not many people who would be interested in discovering monkeys and things had ever gone there,” said Ashley Vosper, a conservation field scientist who snapped the first photo. To the Congolese researchers who accompanied the expedition, he said, the blurry visual of the monkey “just didn’t fit.”

Likweli monkeys managed to avoid further detection for more than a decade. Then, a spate of sightings in 2018 gave researchers an inkling that they had something unusual, and they launched a dedicated project to find the species in the rainforest via foot patrols.

“You go out there for 10 or 15 days. A typical day, you wake up, you pack your stuff, and you start moving,” said Junior Amboko, a field conservationist at Florida Atlantic University and one of the paper’s co-authors. Every time they saw a group of monkeys, they’d stop and have a smaller team of two or three people follow the pack to observe them.

“You have to be as quiet as possible and try to make sure that you can record some behavior, because the idea is not to disturb primates,” he added.

In addition to field observations — 114 of them over four years — the scientists also collected skin, skeleton and tissue samples from three dead monkey specimens to confirm that they had a new, distinct species.

“We brought in every piece of evidence that we could,” said anthropologist Kate Detwiler, another author of the study. “Every piece said, ‘Wow, this is distinct.’”

The estimated range of the Likweli monkey, in the center of Congo, is tiny — only about 650 square miles, or two-thirds the size of Luxembourg. That’s one of the reasons it might have evaded discovery for so long.

However, this region of the Congo basin has yielded new primate species before. In 2012, researchers announced the discovery of the Lesula species, striking for its blue bottom and humanlike eyes. That discovery helped spur the creation of Lomami National Park, where most of the Likweli sightings occurred.

While most locals knew about the Lesula monkey — scientists came across one being held as a pet — only hunters in the area seemed aware of this other species.

John Hart, the new paper’s lead author, helped create a national park where Likweli monkeys live after he and other researchers discovered the Lesula in that same area. Hunting is illegal in national parks in Congo, which afforded the animals some protection.

“We were lucky that included in that park area was the range of this unknown monkey,” Hart said.

To obtain genetic samples, the researchers collected the bodies of Likweli monkeys that had been confiscated from hunters during government patrols. Their analysis estimates that the species split off from its closest relative about 5 million years ago.

Likweli monkeys belong to the genus Colobus, a family of monkeys in West and Central Africa, often with fur in a striking black-and-white pattern. The scientific name, Colobus congoensis, is a tribute to Congo, which Amboko said has never had a monkey species named after it before. Another local name, based on its behavior, is “kasaba nkoni,” meaning branch shaker.

But much else is unknown about the species, such as its mating behavior, diet, or even why it’s confined to such a small geographic region.

“I think it’s going to be a very important species for the ecology,” Hart said. “I also think that once its genomics are fully explored, people are going to know a lot more about the evolution of African primate fauna. ... It looks to be an ancient lineage.”