There are at least two others, the addax were in one, they seem to like the other house, last time I was there one of the addax was standing up to the anakole that was in it. There is another one that probably held some of the lechwe because there are a lot of them and there were not that many out but I couldn't see into that one.
I think they can shut them in the houses but don't think there are any yards.
The stuff behind seems to be owned by Trent Water. I wish they could grow something to screen it off!