I think the perspective of depth is somewhat warped in this picture, if you look closely there are full sized viewing windows behind the trees and they look tiny in comparison. This actually looks like a really nice naturalistic enclosure.
@Giant Panda It looks like a pretty decent size, sure its not huge but more than adequate. How accurately this photo shows the size is pretty subjective. I agree with FunkyGibbon I think it is farther to the back side of the exhibit than it looks at first glance, to hazard a rough guess maybe 9000 sq ft.
@DelacoursLangur 9000 square feet (836 square meters, why do some people still not use the metric system ) seems like an overestimate. It shows you have to be really careful with judging exhibits from pictures...
@lintworm Maybe its a bit high . I was guessing like 35 feet wide and 250 long. On second thought I think im significantly off, probably closer to 30x100. Thanks for checking my overestimate!