Current Biology has a Q and A with orangutan researcher Anne Russon. It's a good discussion to freshen one's knowledge of orangutan behavior. Here's an interesting passage:
Orangutans also show chimpanzee-like traditions, so they too sustain cultures. Given their dispersed sociality, how they do so is unclear. Youngsters learn an enormous amount from their mother, but mostly basics. Consorts could learn from each other, but opportunities are very rare. And neither network can spread traditions community-wide. Adolescents may hold the answer: gregarious and keen on widening their horizons, they range beyond their natal range and hang out with non-kin — probably swapping knowledge and skills and jointly concocting new ones.
This is a bit of a mystery, even in chimpanzees where the geographic distribution of "cultural" behaviors is better known. How do these traits manage to stake out territories larger than a local group, when opportunities for diffusion among groups are so few? Do they go along with dispersing females? Is mother-offspring learning (in chimpanzees, the major "broadband" channel of information transfer) sufficient, or are peers more important? How does transfer differ among behaviors?
Russon herself has a very informative website with resources on orangutan conservation. Russon's 2004 book is Orangutans: Wizards of the Rain Forest (The Amazon page seems like a portal to everyone else's orangutan book, as well).