In fact, orangutans look a bit awkward on the ground, using their arms as we might use a pair of crutches or lifting those arms high above their head when they walk.

Sumatran orangutan: Lives on Sumatra. The hair is longer and lighter-colored than the Bornean species. The adult male’s cheek pads, called flanges, form rigid half circles on the sides of his face and both males and females usually develop beards as they age.

Bornean orangutan: Lives on Borneo. Adult males have much larger flanges and a large throat pouch. The hair is shinier and the females rarely have any beard at all. Bornean orangutans are more heavy-set than the Sumatran species.

Sumatran orangutans, especially younger ones, have to worry about tigers, as well as other predators such as clouded leopards, large pythons, and crocodiles. To stay safe, they tend to spend more time in the trees than Bornean orangutans, which don’t have those predators on their island so can safely spend more time on the ground.