It's been said by the developers that they don't just add creatures to the game if they don't have some purpose or useful drops. This was the response to various AMA questions asking/requesting for creatures such as bears etc.

I want to call the developers out on this, citing two infamously useless creatures to encounter in the game: The Fenrig and the Ghost, among others. Lore and atmosphere-wise, sure they can fit night in the mountains(Werewolves) or lingering spirits in a burial crypt. These things have been around since the beginning though, and drop utter crap.

The Fenrig has a trophy and a wolf fang which wolves drop already, that's it. Wolf fang is garbage sooner than pelts ever will be. The Ghosts drop... absolutely nothing. I don't think I've ever seen a trophy of a Ghost.

So what now? Maybe they deserve some loot? Maybe Fenrigs can drop dark pelts for a DARK wolf cape with a rough look. Ghosts? I dunno.. something ectoplasm for whatever purpose.

Point is, using the bears requests some others make, the Fenrig of Ghost are proof that you can have creatures there that really fit where you find them and add something to the game (just not useful loot yet) so hopefully you devs can keep an open-mind about others. So why not bears in a forest or the mountain(and you're adding caverns too!)? They would make absolutely perfect sense. We already have deer in the meadows. And the bear is a deeply respected animal in the Viking Age as well.