What Gorillas Leave Behind
Mountain gorillas leave a rich trail of physical evidence as they move through Bwindi’s forest: footprints, knuckle prints, nest sites, dung, feeding remnants, and vegetation disturbance that experienced trackers read as fluently as text. The ability to interpret gorilla signs is the foundation of both conservation monitoring and the guided trekking experience. Understanding what gorillas leave in the forest — and what each sign reveals — enriches the trekking experience and provides insight into the daily movements of animals you may not yet have seen.
Footprints and Knuckle Prints
Mountain gorilla footprints are large, distinctive, and structurally different from the footprints of any other forest animal. The foot is humanlike in its basic plantar structure — heel to ball to toe — but considerably wider and with a divergent hallux (big toe) that functions as a grasping digit and leaves a noticeably separated impression on soft substrates. Adult male (silverback) footprints can be 30 centimetres or more in length and 18 to 22 centimetres wide at the ball of the foot, making them unmistakeable even to inexperienced observers.
Knuckle prints, produced by the curled fingers during quadrupedal locomotion, appear alongside footprints in the gorilla’s trackway. The knuckle impressions are oval, roughly 6 to 10 centimetres in diameter for adults, with the characteristic curved imprint of the middle phalanges rather than the rounded impression of a full palm or individual fingertips. The pattern of alternating knuckle-foot-knuckle-foot impressions, with the front-heavy weight distribution typical of knuckle walkers, is distinctive and readable at a glance by experienced trackers.
Fresh prints in soft mud retain moisture and appear dark; older prints show the beginning of drying at their edges. In leaf litter and on harder substrates, prints are less well preserved but the disturbance of leaf surfaces and slight compression of the soil beneath often provides readable indication of passage. Trackers in Bwindi assess print age partly from substrate conditions and partly from their knowledge of where the group was last sighted — a contextual interpretation that experienced rangers perform rapidly and accurately.
Night Nests
Gorilla night nests are among the most unambiguous signs of gorilla presence in any patch of forest. A fresh nest — constructed within the last 12 to 24 hours — consists of bent and broken vegetation forming a recognisable circular or oval platform. The vegetation used is still green or only beginning to wilt; the construction is tight and the platform is identifiably structured. Inside the nest, compressed vegetation retains the impression of the animal’s body.
Older nests show progressive wilting and browning of vegetation, eventual decomposition of plant material, and gradual collapse of the platform structure. An experienced observer can estimate the age of a nest from the degree of wilting and decomposition, providing information about how recently the group was present. Nest density and pattern — multiple nests clustered together — indicates the sleeping site of a complete family group, with the spatial arrangement of nests reflecting the group’s social structure.
Trackers note nest cluster location each evening when they see the group to nest, allowing the following morning’s search to begin from the previous evening’s known location rather than from scratch. This continuity of tracking — each day’s search beginning from the previous day’s last known position — is what makes reliable daily gorilla location possible in dense forest where visual detection from a distance is impractical.
Dung and Faecal Deposits
Mountain gorilla dung is substantial, distinctive, and informative. Individual deposits can weigh 0.5 to 2 kilograms, reflecting the enormous throughput of a large-bodied herbivore processing 25 to 30 kilograms of vegetation daily. The dung is fibrous, roughly cylindrical, and composed largely of partially digested plant material. The smell is distinctive and familiar to experienced trackers — a characteristic odour that can be detected from several metres in still conditions.
For researchers, faecal samples from gorilla dung provide non-invasive access to DNA (for individual identification and genetic analysis), intestinal parasite eggs and larvae (for health monitoring), hormones (including stress hormones, reproductive hormones, and health indicators), and dietary information (from undigested plant fragments). Monthly faecal sampling programmes in Bwindi’s habituated groups provide the health monitoring data that informs veterinary intervention decisions.
Vegetation Disturbance and Feeding Signs
Gorilla feeding leaves unmistakeable traces in the vegetation. Stripped stems with characteristic bite marks, broken branches where gorillas have pulled vegetation toward themselves, discarded leaf material where only the most nutritious portions were consumed, and bark stripped from tree surfaces all accumulate in areas of intense gorilla feeding activity. These feeding signs allow trackers to assess how recently the group fed in an area and how productively — a group that lingered in one spot for multiple hours leaves a denser accumulation of feeding signs than one that passed through briefly.
The Alarm Scent
Experienced gorilla trackers and rangers report being able to detect the distinctive alarm scent — a pungent, musky odour produced from apocrine glands when gorillas are stressed or alarmed — before seeing or hearing the gorillas themselves. This olfactory sign is less amenable to description than visual signs but is reliably identifiable to experienced noses and provides advance warning of a gorilla group’s emotional state during approach.
Final Thoughts
The ability to read gorilla signs transforms a walk through Bwindi’s forest from a nature walk into a detective exercise. Trackers who lead gorilla trek groups are reading a continuous text written in bent vegetation, pressed mud, and scattered dung — a narrative of where a family of gorillas slept, what they ate, how they moved, and what they encountered. Visitors who pay attention to these signs on their way to the gorilla encounter often arrive with a deeper appreciation of the landscape that the gorillas inhabit and the life they live within it.
