The ISIS listing is a little confusing, with different numbers being listed under 'group' and the normal section, but I'd be surprised if there were more than 100 animals on this island. Even that number presents a wonderful spectacle, and this is one of the great European zoo exhibits. Not sure what the micro-management of the baboons is like, though.
Good exhibit and visitors' favorite. But it is overcrowded and zoo is trying to curb breeding. When one baboon moves, a whole row of animals along a narrow ledge has to move - animal traffic file!
It should hold no more than 40-50 baboons in my opinion.