Amy thanks for your question. Without entering into a debate about the value of zoos hopefully I can address part of your question. Stephen is currently very busy but he'll hopefully blog again at the start of next week. The assumption should not be made that just because orangutans spend a lot of time alone in the wild that this behaviour must be replicated in captivity. How solitary a wild orangutan is depends on factors such as food availability or type of forest habitat. For example, Sumatran orangutans are observed to be more social during times of increased fruit availability. If the habitat allows a higher density of orangutans then social behaviour is more likely to be observed. If food is scarce and long distances have to be travelled then orangutans don't necessarily have the time or energy to invest in social interactions. Zoos often keep orangutans in small family groups, an adult female orangutan with her infant and perhaps juvenile offspring and this reflects a grouping that is observed in the wild.
What is certain is that there still remains a great deal to be learnt about this highly intelligent great ape!