Nyungwe's troops of Angolan black-and-white colobus monkeys are among the largest recorded anywhere — groups of 300 to 400 animals have been observed moving through the canopy together, which is unusual for a species that typically lives in groups of 20 to 30. The reasons are not fully understood: the forest may be unusually productive, or the absence of large predators may allow super-troops to form.
The tracking trip from Gisakura takes a half day. Sightings are reliable — the troops are loud, large, and habituated to observers. You also have a good chance of encountering grey-cheeked mangabeys and L'Hoest's monkeys on the same outing. The hike is moderate; mostly forest tracks rather than the steep scrambles required for chimps.