The dwarves selectively bred owlbears for toughness, ferocity, and slightly more discipline and intelligence. They also managed to introduce a bulette trait they considered desirable into the creatures: specifically, the ability to burrow rapidly. The dwarves termed the result "dire owlbears," although that label isn't really correct. Most "dire" creatures are primitive branches of a family tree that managed to survive for eons unchanged from more savage versions, usually in isolated regions far from civilization.