Orangutans are a kind of Apes that can only be found in Asia.
Although some fossils have been found in China, Vietnam and Laos, they currently leave ONLY in Borneo and Sumatra island, which were a unified land until 40.000 years ago.
When the two areas divided, Orangutans, leaving on both sided, developed many important characteristics and were classified as separate species in the late 90’s.
Sumatran Orangutans were the first orangutans to be classified as critically endangered, unfortunately, they have been recently followed by the Bornean Orangutans as well.
There are 3 subspecies of Bornean Orangutans and many argues that Tapanuli Orangutan is more similar to the Sumatran Orangutan, but smaller and with frizzier hair.
Orangutans have been recently classified as the smartest of the Great Apes.
They use various tools, such as leaves to cover themselves from the rain, or sticks to clean their teeth, they can be taught to use a hammer to nail structures together and even siphon liquids through a hose. It is not just the capacity of imitating that make the Orangutan smarts, but is the ability to understand why we complete these actions and use them in the wild when they might be helpful, and it has been observed that Sumatran Orangutans use more tool.
Also, it has been compared the problem-solving ability of the 2 species.
It has turned out that Sumatran Orangutans (more gregarious and social tolerant) showed superior innate problem solving ability, together with more caution and less rough exploration style.
This experiment supported the cultural intelligence hypothesis according which among two sister species the most sociable is the one with higher intellectual abilities.
In fact, the greater the quantity and quality of social inputs an individual (of a species that learns socially and transmits this knowledge across generations) receive, the more learned skills an individual can acquire. Also, the more experience it can accumulate the better it will be at asocial learning or problem-solving.
(If you want to learn more about the cognitive differences between orangutans and the cultural intelligence hypothesis check https://www.nature.com/articles/srep30516)