I see that the base of some of those trees are hotwired, along with the line of hotwire down by the water's edge. This is very much an 'open' exhibit, with little canopy for the gorillas and probably not a lot for them to do. I've never visited, but I've always thought that this is a poor example of a gorilla enclosure.
A photo like this one portrays a bleak picture, even with the painted trees on the white wall:
