Nice interview touching on Carel van Schaik's new book, Among Orangutans : Red Apes and the Rise of Human Culture. Much on van Schaik's observations of orangutan sociality in densely occupied forest, including tool use (via Gene Expression).
Q. What were you looking for in the Suaq swamp?
A. We'd been working in a mountainous area in northern Sumatra, and it felt as if we were missing the full picture of orangutan social organization. All higher primates - all of them - live in distinct social units except for the orangutan. That's a strong anomaly, and I wanted to solve it.
Q. How was Suaq different from other orangutan habitats?
A. It was an extraordinarily productive swamp forest with by far the highest density of orangutans - over twice the record number. The animals were the most sociable we'd ever seen: they hang out together, they're nice to each other, they even share food.
And this is an interesting thought:
Q. Were orangutans more social in the past?
A. I guess the rich forest areas that allowed them to live in groups were much more common in the past - they're the ones that are best for rice growing and farming - but there's no way of knowing for sure.
Orangutans and their relatives used to live across a huge swath of East and Southeast Asia, so it is very credible that much of their current habitat on Sumatra and Borneo is actually relatively marginal compared to their former range. Are most of today's orangutans a shadow of a formerly very gregarious species? And how related is their highly arboreal existence to their long life history and exceedingly long interbirth interval? They are a very interesting species from that regard -- a true survivor of the Miocene age of the apes.