|Orangutan resting in a tree|
Orangutans are species of great apes belonging to the taxonomic genus Pongo. The name Orangutan means "man of the forest" in the Malay language. There are two living species: the Bornean and the Sumatran, and one that is extinct (P. hooijeri). Because they depend so greatly on trees, they have become endangered due to large amounts of deforestation. There are 41,000 Bornean orangutans living today while only 7,500 of the Sumatran orangutans still live. Orangutans are highly intelligent and have an intelligence that is similar to that of a human. 
Orangutans have long, red or orange fur. They are around four to five feet tall with an arm span of about seven feet from fingertip to fingertip. Orangutans have long, powerful arms and grasping hands and feet that enable them to be more efficient while in the trees. They can weigh up to 200 pounds. Male orangutans can be either flanged or unflanged. Flanged males have prominent cheek pads called flanges and a throat sac to make loud noises called long calls. Unflanged males look like adult females. It is possible for an unflanged male to become flanged. Sumatran orangutans have longer facial hair than Bornean orangutans.
Female orangutans have a reproduction system that is very similar to that of a human. They menstruate with a cycle that lasts around 30 days. Orangutans reproduce sexually. The female has a gestation period of about nine months. They give birth to a single infant about every eight years. This allows the mother to give her child all the attention it needs. Young orangutans stay close to their mothers for 6 or 7 years after birth until they are developed and able to care for themselves.  When born, an orangutan weighs around 3-5 pounds. There are three stages of development: infant, juvenile, and adolescent. A female reaches adulthood when her first infant is born. This happens at around 14-16 years. A male reaches adulthood when his laryngeal throat pouch, cheek pads, and long call emerge which usually happens when they are 18-20 years, but it is possible for this to occur earlier in life.
Orangutans are very dependent on and spend most of their time in trees. They live in the tropical rainforests of Sumatra and Borneo. Bornean orangutans do move around on the ground more often than Sumatran orangutans. Orangutans make nests in trees from vegetation. Their diet consists mostly wild fruits such as lychees, mangosteens, mangoes, and figs. They often eat leaves and insects as well. Orangutans drink water out of holes in trees. Though they are mostly herbivorous, they do eat meat on rare occasions. 
Orangutans are extremely intelligent animals. They possess human-like mental abilities. Orangutans have been known to imitate humans. This can be seen in the acts of sawing wood, hammering nails into wood, combing their hair, and making hammocks. They are able to figure out new ways to use the objects they find. An example of this is making tools out of sticks or rocks. A mother teaches skills to their young such as how to build nests and which foods are not to be eaten. Leaves are of much importance to orangutans. They are used as umbrellas, fly swatters, for holding spiny fruit when opening them, and even as toilet paper. Sticks are useful to orangutans when they need to open something, dig holes, or reach a further distance. Orangutans make cups, swings, and ladders out of what they are able to find. Orangutans are able to efficiently learn and understand sign language. 
An Orangutan imitating a boy in Borneo.
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