Orange lips and a froglike roar: New monkey discovered after 18-year search in Congo rainforest

A blurry 2008 photograph led researchers on an 18-year search to confirm a new monkey species. Almost two decades after an unusual monkey was first sighted in the treetops above a Congo rainforest, an international team of researchers has described it as a new species. Small, orange-mouthed and living in what is today part of Lomami National Park in the Democratic Republic of Congo, the monkey is known as Likweli among the members of the Balanga ethnic group. In scientific annals, it’s now officially described as the Colobus congoensis – the sixth species of the Colobus monkey, all native to Africa. “Our team evaluated multiple datasets that all reached the same conclusion: Likweli is a distinct species of Colobus monkey we haven’t seen before,” says Julia Arenson, a postdoctoral fellow in Yale’s Department of Anthropology and the Yale Institute for Biospheric Studies, who co-authored a study that formally recognised the monkey. “Discovering a primate species is exceptionally rare, especially from populations previously unknown to science.” A blurry clue in the canopy For the researchers, a fleeting glimpse of this curious creature eventually became an 18-year investigation. In 2008, researchers photographed an unfamiliar black monkey high in the rainforest canopy. While the animal looked unfamiliar, the image was too blurry to determine whether it represented a species unknown to science. A decade later, a second sighting revived interest and prompted a research project. “Only after 10 years of exploring the Lomami Forest did we have enough clear views and convincing photos to allow us to say that there was yet another new monkey,” says co-author Terese Hart. “This primate was not only new – it was extremely rare and with a limited range.” Between 2018 and 2022, scientists surveyed forests, recorded the monkey’s roaring, froglike calls, analysed genetic samples and interviewed residents in 52 villages bordering the animal’s range. The researchers documented 114 sightings across roughly 1,700 square kilometres of forest, but the monkey still proved elusive. Residents in only eight of the villages they surveyed recognised the species – notable because the communities had extensive knowledge of the wildlife around them. Study lead John Hart credited the discovery to the Congolese researchers who first realised they were looking at something unusual. “The discovery and documentation of the Likweli never would have happened without our team of Congolese explorer naturalists,” he says. “These field leaders recognized when they were in front of something they did not know. They put in the extra effort needed to document and confirm it.” A rare find with urgent implications Published in the scientific journal PLOS One, the findings make the Likweli just the fifth African monkey species to be described from a previously unknown wild population in the past 75 years. Researchers estimate that the monkey occupies a limited area of forest between three tributaries of the Congo River and warn that hunting and expanding human activity threaten its survival. The team has also recommended the species be classified as endangered. “This is a rare discovery with significant conservation implications,” says Eric Sargis, professor of anthropology at Yale University. Now, with Colobus congoensis officially recognised by science, the researchers hope its discovery will help draw attention to the need to protect Lomami National Park, its extraordinary biodiversity and the species yet to be discovered there.