How smart are orangutans?

Related posts:

1. Red-heads get free entry to zoo on World Orangutan Day!!!
2. How an orang-utan cools itself...
3. Orang-utans know how to give and take favours...
4. Good thing these monkeys are not customs officers!!!
5. Living with orang-utans...
6. How a chimp prepared his weapons to attack humans...
7. The amazing intelligence of crows...