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A wild adult silverback mountain gorilla usually weighs around 140–200 kg (about 300–440 lb), roughly twice the weight of an adult female, which typically weighs 70–100 kg. Eastern lowland (Grauer’s) gorillas are the largest gorillas and can be heavier, and gorillas in zoos often weigh more than wild ones because they eat richer food and move less. Most of a silverback’s weight is muscle in the chest, shoulders and arms, which is why he looks so massive up close.
Males, females and young
Gorillas show one of the biggest size differences between the sexes of any primate. Females reach adult size at around ten years old. Males keep growing into their teens: as blackbacks, at roughly 8–12 years, they are larger than females but not yet fully grown, and they become silverbacks, with the silver saddle of hair on the back, at around 12–15 years. A newborn gorilla weighs only about 2 kg, smaller than many human babies. See our guide to gorilla life stages and lifespan.
Why wild weights vary
Wild gorillas are rarely weighed, because doing so means sedating them, which vets only do for medical treatment, such as removing a snare. Published weights therefore come from a limited number of measurements and from comparisons with zoo animals, which explains why figures online differ. A silverback’s weight also changes with age, health and season: older silverbacks lose condition, and those that have recently fought or been ill may be lighter. Captive gorillas sometimes exceed 250 kg, but this is not typical of wild animals.
What it takes to fuel a silverback
Mountain gorillas eat mainly leaves, stems, shoots and pith, which are low in energy, so they must eat a lot: an adult male can eat around 20–30 kg of vegetation a day. Much of the day is spent feeding and resting while a long gut digests the plant fibre. Bwindi’s gorillas also eat more fruit when it is in season. See our guide to what gorillas eat.
Seeing a silverback up close
On a gorilla trek, you keep at least 7 m from the gorillas, but a silverback sometimes walks past much closer, and his size is one of the things visitors remember most. Despite their strength, silverbacks are generally calm with habituated visitors who follow the rules; a chest-beat or bluff charge is a warning, not an attack. See our guides to what to do if a gorilla charges and the silverback’s role in the family.
Frequently asked questions
A wild adult silverback mountain gorilla usually weighs about 140–200 kg (300–440 lb).
Usually about 70–100 kg, roughly half the weight of a silverback.
The eastern lowland (Grauer’s) gorilla is the largest subspecies.
Around 20–30 kg of vegetation, mostly leaves, stems and shoots.
