As other's have said, RAW it's pretty clearly only possible to use it with a warhound. However if your opponent is ok with it (and I would be), I don't see why you couldn't use it for an animal companion in a campaign. Perhaps not with a bear, but at least with, say, a wolf.
Although, given how much better bears are than pretty much any other animal companion, I'm not sure why you wouldn't take one.