A new Congo monkey arrives with a 1,700 sq km range and almost no sighting record

A team including Junior Amboko, a doctoral student in biological sciences, and anthropologist Kate Detwiler has described Colobus congoensis, known locally as Likweli, from a remote corner of the Democratic Republic of Congo ^[3]. It is one of only five new African monkey species described in the past 75 years, against a world total of 536 monkey species ^[2][1], but the number that should hold an operator's attention is the size of its known range: roughly 1,700 square kilometres, about 660 square miles ^[9].

The animal itself is unremarkable in build and distinctive in detail. It is a relatively small colobus of about 7 kg, with silky black hair, a long black tail and, like all colobus monkeys, no thumbs ^[5]. Its face is black and dark grey, framed by long spiky black hair running across the forehead; the pale orange-cream skin around the mouth and under the nose is its most striking feature, conspicuous when the animal makes its deep roaring calls, and there is a bright white patch at the base of the tail ^[6].

The species case rests on more than pelage. According to the team, genetic analysis put the split between the ancestors of Likweli and of Colobus satanas at about four to five million years ago, considerably deeper than they had expected ^[7]. The two species now sit more than 1,200 km apart, separated by several major rivers, which turns the description into a question about how the Congo Basin's rivers have shaped mammal distribution over geological time ^[8]. Vocal evidence was gathered separately: roaring calls recorded at six locations in Lomami National Park and compared against those of close relatives ^[13]. The full case drew on years of searching on foot and by canoe, field observations, photographs, audio recordings, and genetic and anatomical analysis ^[15].

The cost of that evidence explains the sighting record. Reaching the forest requires a flight, a motorcycle ride, two days of hiking and a dugout canoe, with no paved road access ^[12]. The team visited 52 villages, asking residents and hunters what animals they had seen, what they called them, where, and whether they hunted them, then asked those who described something like Likweli to guide them to the spot ^[11]. Even so, the monkey is rare, shy, usually high in the canopy, and rarely seen by the communities living beside its habitat ^[10]. Despite the orange mouth patch, locals have reported only a few sightings since 2008 ^[4]. Moving biological samples out of the DRC for analysis required lengthy paperwork ^[14].

That is a description without a demography. The published account carries no population estimate, no formal conservation assessment and no figure for hunting pressure, and the team has not yet studied what Likweli eats, though colobus monkeys generally take leaves, flowers and fruit and disperse seeds as they do ^[16][17]. Five African monkey descriptions in 75 years works out to roughly one every 15 years ^[18], so the taxonomic event is genuinely rare. The operational problem is that the species enters the record already scarce, hard to reach and confined to an area smaller than many single logging concessions, with the survey work that would size the population still outstanding.