Orangutans have high cognitive abilities and have been seen making simple tools with which to scratch themselves, using large leaves as umbrellas to shelter themselves from the rain and even using branches as tools during insect foraging. It helps that they have opposable thumbs like humans, as well as opposable big toes, making such activities possible.

There are now three known species of orangutan: Bornean, Sumatran and the recently discovered Tapanuli orangutan. There are also two different types of adult male orangutan - flanged and unflanged. Flanged males have prominent cheek pads called flanges and a throat sac which enables them to make 'long calls', which can be heard for miles around (think King Louie from The Jungle Book). Unflanged males look more like females, and can change to flanged males over the course of their lifetime.

Trek through the rainforests of the Danum Valley in Malaysian Borneo and the Gunung Leuser National Park on the Indonesian island of Sumatra, or spend days drifting down the Sekonyer River in Kalimantan's Tanjung Puting National Park in a traditional klotok houseboat to see orangutans at the park feeding stations. See them in semi-wild sanctuaries in Sepilok or Semenggoh where, especially at feeding times, you can really get up close and learn about their different personalities from the guides.