I can recall straining my eyes in an attempt to locate a pair of tiny duiker on many zoo visits, and if I'm not mistaken the zoo has held the species in this exhibit for probably close to 20 years. However, now it is home strictly to a pair of geriatric colobus monkeys and a couple of platforms and several vines have been added to the canopy. There is a young pair of duikers at the zoo but they will be kept off exhibit to encourage breeding while the monkeys have this magnificent exhibit all to themselves. It is really a disappointment as there is already a troop of 3-5 younger colobus monkeys in an enclosure just down the trail, and so to have two slow-moving, elderly ones in this large habitat seems a shame from a visitor's perspective.
I have no idea. The zoo will be dealing with a rash of elderly primates in the future as 2 colobus monkeys, 2 orangutans and 2 gorillas are all approaching the end of their lifespan within the next decade or less.