These great apes are peaceful, family-oriented, plant-eating animals that live in complex social groups. They are the largest of all primates. Their arms are much longer than their legs, and gorillas can use the backs of their fingers like extra feet when they walk—a practice called the knuckle walk. Like all great apes (except humans), gorillas require rain forests to make their living, and the forest depends upon them, too. The gorilla’s fibrous scat acts as rich fertilizer for the forest, and seedlings sprout from it rapidly, making these animals important forest regenerators.