There ARE werebears in Dawnguard. It's the big Dawnguard secret. The Dawnguard members will be able to become one.

-The new Lycanthropy perk tree will apply to the new form as well. Werebears are slower than werewolves, but can unleash devastating charging attacks.

- You can't be both a werewolf and a werebear.

- There's an all new quest involving the Prince of the Hunt.

- Lycanthropes get a damage bonus against vampires.