Can I ask why it is a bad idea? I've observed this combination twice (in 2009 and two weeks ago) and on both occasions the animals seemed pretty relaxed.
This mix has been at the zoo for a long time (almost 10 years) and there has never been any problems. They essentially ignore each other. The bisons are far too big for the black bears to consider them as possible prey and the exhibit is very large. The exact same mix is at Safari Parc Peaugres and if I remember right there's a third place with it (the name escapes me).
Interesting combo. And as someone who has lived in areas where these animals occur in the wild, I can say this isn't a bad combo. How common are bison and black bears in European zoos?
