Thank you for all your comments and I'll do my best to respond to them soon. Another interesting thing happened on Sunday at Camp Leakey: Siswi almost completely submerged herself in water. Orangutans can’t swim though they do wade. The rehabilitated, ex-captives at Camp Leakey will also play with water but that is probably a behaviour learnt from watching the staff. What made Sunday interesting was that Siswi spent so long in the water. She sat there for a good fifteen minutes and actually bobbed up and down so the water rose up to her chin.
Siswi - adult female orangutan in the river.
I am quite convinced she was simply trying to cool off. However, that does not fully explain a) quite how an orangutan’s natural wariness of water could be so totally overcome; let’s not forget there are crocodiles in these rivers and b) how an orangutan who instinctively shelters from rain, which makes them cold, would on another occasion use water for exactly that purpose.
Siswi sitting in the river
Who knows whether Siswi would have sat in the water for so long if we had not been there and it is not a huge intellectual leap to realise water makes you cold and you can choose when you want to be cool or dry. However, none of that dry scientific reasoning detracts from the interest: orangutans are fascinating!