Of the nine primate species recorded in Bwindi Impenetrable National Park, the red-tailed monkey (Cercopithecus ascanius) is one of the most frequently encountered on gorilla treks—and one of the most rewarding to observe for visitors who take the time to look upward into the mid-canopy. Loud, social, and acrobatically impressive, red-tailed monkeys represent the kind of forest wildlife encounter that enriches the gorilla trekking experience beyond the habituation encounter itself.
Identification and appearance
Red-tailed monkeys take their name from the distinctive chestnut-red colouration of the underside of their tail—visible when the animal moves at speed through the canopy and momentarily extends the tail as a balancing aid. The face is also diagnostic: a white cheek patch on each side and a prominent white spot on the tip of the nose give it a distinctive “painted” appearance that distinguishes it immediately from other Bwindi monkeys. The body coat is olive-brown to grey, and adults weigh 2 to 4 kilograms—significantly smaller than colobus monkeys but larger than Bwindi’s smallest primates.
Troops of red-tailed monkeys typically contain 7 to 30 individuals, usually with a single dominant adult male and multiple females with offspring. They are vocal and somewhat confiding when accustomed to human presence—troops that regularly encounter trekking groups on gorilla trails become habituated to human noise and movement and may remain visible for extended periods rather than fleeing immediately at the group’s approach.
Diet and habitat use
Red-tailed monkeys are frugivore-insectivores: their diet includes forest fruits (particularly small figs and berries), leaves, flowers, and arthropods captured by leaf-searching and bark-gleaning. Their small, dexterous hands and quick movements through the mid-canopy reflect the ecological role of an opportunistic forager that exploits multiple food types across the forest vertical profile. In Bwindi, red-tailed monkeys regularly associate with grey-cheeked mangabeys in mixed-species foraging groups—a pattern that provides each species with enhanced predator detection and access to food sources disturbed by the other’s foraging activity.
Red-tailed monkeys interact with mountain gorillas in complex ways. Gorilla groups moving through an area may displace red-tailed monkey troops from preferred feeding trees, but the two species also exploit the same Ficus fruiting events, with monkeys feeding in the upper canopy while gorillas consume fruits that fall or that they pull from lower branches. Direct aggressive interactions are uncommon—the size differential makes the outcome of any confrontation predictable, and both species typically avoid escalation.
The best time to observe red-tailed monkeys on a gorilla trek
Red-tailed monkeys are most active and most visible in the first two hours after dawn, when they emerge from overnight roosting positions and begin active foraging. For gorilla trekkers departing the briefing at 7:30am, the walk to the gorilla group often takes place during this morning activity peak. The combination of good light, active monkey behaviour, and the absence of the midday torpor that characterises all warm-blooded forest animals in the early afternoon makes the pre-gorilla section of the trek the optimal monkey observation window.
Ask your ranger guide to point out red-tailed monkeys when they are visible—guides who know the trails know which fruiting trees reliably hold monkey troops and can direct attention upward at the right moment. A small pair of binoculars (compact 8×25 or 10×25 binoculars add minimal weight) transforms brief glimpses of movement in the canopy into fully resolved portraits of individual animals—and reveals the white nose spot and chestnut tail that distinguish red-tailed monkeys from the other primate species sharing the forest.
