Orangutans are two species of great ape that live in the rainforests of Borneo and Sumatra. Their name comes from Malay phrase orang utan, which means "man of the forest." Early translations of the term used -ng instead of -n, making it "orangutang," but this is incorrect, only deriving from the temptation of Westerners to repeat the end of the first syllable on the third. The real world is pronounced just like it is spelled: orangutan.
The orangutans are famous around the world for their high intelligence, their placid (calm) nature, their long red hair, and lengthy arms. The two species are the Sumatran Orangutan, found on the island of Sumatra, and the Bornean Orangutan, found on Borneo. The Sumatran Orangutan is critically endangered, with only about 3,500 individuals living in the wild. The Bornean Orangutan is "only" endangered, with about 45,000 individuals in the wild. Together, the orangutans are the only great apes native to Asia (the others -- humans, chimps, and gorillas -- are all native to Africa).
With the males of the species growing up to 5 ft 9 in (123 cm) in height, and weighing up to 260 lbs (118 kg), the orangutan is the world's largest arboreal animal -- it spends its time almost exclusively in trees. This distinguishes the orangutan from other great apes, none of which are very arboreal. As arboreal animals, fruits make up 65% of the orangutan's diet. They are especially fond of figs. Lowland forests are favored by orangutans for their high fruit content, but unfortunately these are the same forests that are in great demand for logging.
Unlike the other great apes, orangutans are basically solitary, with males and females only coming together to mate. There is also great sexual dimorphism, with males being more than a foot taller and weighing around twice as much as the females. Male development is bimodal, with "flanged" males possessing numerous secondarily sexual characteristics such as a throat pouch, long fur, and the characteristic cheek flanges. Flanged males have a completely different hormonal pattern than unflanged males -- only flanged males defend territories, for instance. Flanged males establish harems over territories, soliciting female attention with calls, but unflanged males can only procreate by rape. A study of orangutans in Sumatra found that each strategy was about equally effective in impregnating females.