This is without a doubt the greatest orangutan exhibit in zoos today. Actual rain forest to live in, live trees to climb on, and pretty much control over the whole zoo. It's also, as far as I'm aware of, the only zoo with free-ranging great apes.
Whilst this exhibit is certainly unique and is able to provide a great space for the orang-utans to live in, I think many Zoochatters aren't seeing the limitations of this set up. The apes that live here are mostly young or more docile females and are restricted to the tops of a select few trees through the use of hotwire. They definitely don't have control over the whole zoo. Singapore Zoo also has two more traditional exhibits where the adults are kept.
A large group of Bornean orang-utans live on an island (quite basic lawn and tree trunks) and the Sumatrans live in a meshed exhibit that seems pretty out of place in the relatively cage free Singapore Zoo.
