Forgive me if I'm mistaken, but I believe that this is the Pere David's deer enclosure, in which case the pond is absolutely appropriate for this water-loving deer species. Also, beaver would not be geographically appropriate with this species.
I'm thinking North American or European Deer. I've never been there and was only thinking in terms of those two continents. I guess it would be quite appropriate for Chinese Water Deer as well. Can't really make out species from this shot though. Have you been to Bronx Zoo before Ituri?
I haven't but I know there collection pretty well and I've seen photos of most exhibits, so I was judging off the exhibit as to which species it was, and I see that I was correct.
