Gorillas are large apes. They can be strong like chimpanzees and orangutans. An adult male gorilla can weigh up to 225 kilograms and stand 1.8 meters in height. Gorillas live in family groups called troops. They have a broad chest, wide shoulders, short legs, and long strong arms. They have black skin and hair. Adult male gorillas' hair becomes silver/grey on their backs as they become older. Because of that, older males are called "silverbacks".