I think it's probably a zoo trying to shake off some of its past. Certainly it still feels a very traditional German zoo - even the relatively recent Asian cat (and these days Fossa) house feels very traditional. Houses like this one and the rhino house feel distinctly of their time, and there are lots of indoor-only exhibits (Bird House, Grizmek House etc), which is probably not how exhibits for many of their inhabitants would be approached now.
