The free-ranging wallabies, muntjac and Chinese water deer date from the very early days of Whipsnade; they are mentioned as being free-ranging in the early 1930s guides.
Free-ranging maras date from a little later but have certainly been present for many decades.
Compared to Reeves' Muntjac, Chinese Water Deer haven't spread far in England. Having been familiar with them at Whipsnade for over 30 years I am liable to be surprised as to just how uncommon the species actually is in captivity.
I think that is probably because they are more specialist- reedbeds and marshes being their true home. They are common in the Norfolk Broads for example. You probably know that unlike most deer they can have multiple litters of up to half a dozen young or so. I saw one at Hickling Broad with babies climbing all over/round it.
