The great apes are the pinnacle of evolution. They include orangutans, chimpanzees, gorillas — and humans. Two species of orangutans live in Borneo and Sumatra, respectively. Two species of chimpanzees live in Africa, including the common chimpanzee and the bonobo. Three species of gorillas live in Africa, including the western lowland, eastern lowland and mountain gorillas. All of these wild apes are considered threatened or endangered.

Unlike monkeys, apes lack tails. For example, chimps are apes, not monkeys.

The orangutans pictured here were in the Sabah Province of Borneo and at the Singapore Zoo. The images of chimpanzees come from expeditions to Gombe Stream & Mahale Mountains National Parks in Tanzania, and Kibale and Queen Elizabeth National Parks in Uganda. Odzala National Park in the Republic of the Congo is the site for the western lowland gorillas, viewed during a 4-week camping expedition, while Bwindi Impenetrable Forest National Park is the site for the mountain gorillas.