It is definately one of the Rhino paddocks and the idea was to mix the two species. There is a rhino house and yards at the top end of the enclosure nearest the Mansion. I guess the two species would just be given access to the paddock at the same time.
I didn't know they had already mixed them. I wonder if it has been stopped or just that they weren't out together on that day for some reason?
I think there was a news article that focussed on the mixing of the two species, and they claimed it had been very successful at first. I really don't know why they stopped it.