Are DeBrazza Monkeys not exhibited here any longer? They were here for years, but I remember reading about them "escaping" a few years ago. The original inhabitants of this extraordinarily beautiful exhibit were Lion-tailed Macaques, who could essentially leave the island whenever they wanted to (to forage in the trash cans next to the old Primate House, among other things), but always returned on their own. This was one of the first exhibits built under the famous 1976 master plan, and still one of the nicest anywhere.
I too remember seeing DeBrazza monkeys here perhaps a decade ago, and there are still a few DeBrazzas at the zoo but they are all off-exhibit behind the scenes. I believe that it was last year when the monkeys were reintroduced to the enclosure, but within a few hours one had leapt to freedom. Since then it has only been a showcase for duikers, which are extremely difficult to find amongst the lush foliage. This enclosure, along with the adjacent red ruffed lemur exhibit, are sheer brilliance in terms of naturalism. I agree that 30 years later they are exceptional, and are a pair of the best enclosures in the world for the species that occupy them.