Were the baboons constructing some type of spaceship in the middle of their enclosure? Perhaps they were attempting to blast out of their brutal exhibit.
They succeeded in so much as they now live on a larger 'earthy' island in a different location. Not a very attractive exhibit either but they do have a lot more room.
Thanks for posting the photo. I have one of the Baboon Island taken in the 70's.. it seemed more bare then. Whenever I left work, one of the male Baboons used to be sitting right at the top waiting for me and would rush down making hell of a noise, so all the other Baboons would join him. This caused the crowd of people looking at the Baboons to turn their heads wondering what they were all looking at... ME! lol As soon as I got to the fence and shouted his name, the male baboon used to do his party piece... put his head on one side and stick his tounge out at me.. it certainly made everyone laugh.. and I thought it was hilarious every single time he did it! lol