Looks ok to me, especially for just one elderly bear. I'm sure you've read on here that Dudley's hand are very tied regarding listed buildings, this is part of one.
Photo's of these bear pits never do look good as they can't show the true size of them, IMO they are perfectly good for the bear, and the tiger one is even better.
I'd agree with Dom, the tiger pit is slightly bigger than the bear pit, also it's got much more cover, when the trees are in full leaf, it's sometimes hard to spot Sarah.