I agree. This particular animal (as well as the black panther) was pacing back and forth and rocking the wire as if it was contemplating going insane. Keeping a single baboon in a tiny wood-and-wire cage is animal cruelty regardless if a place is a rescue center or not. If there is not a single alternative then I'd in all honesty suggest euthanasia.
A new primate house is the next big order of business after the new hippo house. Hopefully this will give the zoo a chance to make introductions between the different olive baboons at the zoo.
