An adult male mountain gorilla, called a silverback, can weigh 180 kilograms - more than two grown-ups put together. Despite their size, they are vegetarians. They spend their days quietly munching on bamboo shoots, wild celery, thistles and around 100 other kinds of plant. A big silverback can eat 30 kilograms of leaves in one day.
Mountain gorillas live in families of about 10 to 30 members, led by one silverback father. He decides where the family will eat, where they will sleep, and where they will travel. The mothers, aunties and youngsters live close together. Baby gorillas ride on their mothers' backs and play in the trees, just like human toddlers play in a park.
Each gorilla has a unique nose-print, like a human fingerprint. The bumps and wrinkles on their noses are all different. Rangers use nose-prints to recognise individual gorillas, and every gorilla in Rwanda has a name. Some are named at a special ceremony every year called Kwita Izina.
Gorillas share around 98% of their DNA with humans. They yawn when they are tired, hug each other, laugh when they are tickled, and grieve when a family member dies. Scientists who study them say that meeting a gorilla family in the forest feels like meeting cousins you have never met before.