The species
The Rwenzori black-and-white colobus is the signature primate of Nyungwe. It is a leaf-eater, almost entirely arboreal, with a long white mantle and tail against a black body. Colobus have no thumbs — an adaptation for hooking through branches at speed — and watching them launch across gaps in the canopy, with that long hair fanning out behind them, is the reason people book this trek.
Why the Nyungwe troops are unusual
Colobus are sociable everywhere, but the Nyungwe animals move in semi-habituated troops of several hundred, which is exceptional. The park holds the largest arboreal troop of black-and-white colobus ever recorded. Practically, this means that once you find them, you have found a lot of them — sightings are not a matter of glimpsing one animal.
A group has also settled near the main campsite area, so a few are often visible without walking at all. Going deeper with a guide gets you closer and gives you the troop rather than the strays.
What the trek is like
Considerably gentler than chimpanzee tracking: a later start, shorter distances, less altitude and a much higher success rate. It suits anyone who wants a serious primate experience in Nyungwe without the pre-dawn start and the hard walking. There is a separate, easy colobus population in the tea estate just outside the park boundary — worth knowing if mobility is a constraint.
Booking
Colobus trekking is booked as a park activity through the Rwanda Development Board rather than as a permit in the gorilla sense, and it is far easier to arrange at short notice. See visas and permits for how the park activity fees work.