One of those odd questions that pops into ones head. Free ranging Animals/Birds not domestic that you have seen in mixed Zoological Collection. I think whipsnade used to/still does have wallabies & mara and Shepreth used to have A couple of Squirrel monkeys roaming free. Any others you can chuck into the mix
Whipsnade still has lots of free-ranging wallabies, mara and Chinese water deer. There are still a few Reeves' muntjac too although I haven't seen any of the latter on my last two visits.