My main point was that there are two or three very similar enclosures in the African section and this is an example. But I certainly didn't notice that this particular one was signed for mangabey. If you look at this indoor enclosure it looks like it links to the outdoor one featured here so I wonder if there is some rotation going on here.
Always a big fan of rotation so hopefully! Although on second thought it looks like a fixed sign so unless there are others out of frame I doubt it is rotational.