tbh bunny dungeon would be better than fox, badger, bear or wolverine dens, imagining it, they would all play out the same, hoards of animals spawning in waves, the game wouldn't feel the same anymore + those aren't type of animals that live in packs... troll villages are okay, rabbit burrows are nice, maybe even moles, but please don't add a dungeon for every single animal type, and for those that you do, don't make them play out the same hoard killing wave after wave as it'll get boring really fast, and make animal encounters outside less interesting/meaningful. maybe add actual creature dungeons instead, that follow the game theme instead and make them expand over time.
the wolf den for example, might be an interesting idea but i feel it'd be more interesting if they were to hunt in packs in the outer world and make it dangerous to travel solo in their territories. raiding a wolf den would make them spawn less often for some time, but if you want to hunt them for their resources, make it so that not attacking a wolf den would actually be more beneficial than going in and committing a genocide as soon as you see the den spawned. if the wolf dens would expand over time making more wolves spawn in the area until they become a real problem if kept untouched for too long, becoming visually bigger (both wolves and the den) and making wolves inside stronger (not more in quantity), it'd be something fun to see and experience.
maybe even do the same for the beavers, and have more beavers around the dam, less inside (than there is now), but make them more dangerous with more abilities, such as causing the ceiling to collapse by breaking down their own supports, like a cave-in with logs and debris, so you'll have to focus and kill those asap.
for the bears, i can't imagine large packs spawning like they did at the end of the first 3d world, even though it was fun, but it'd be really silly and make the bear resources less valuable. mini-dungeons might work with 2-3 bears inside, being more dangerous and doing aoe attacks or even fear stuns, just having them spawn near and inside already existing burrows at rare occasions, maybe even jumping out of the burrows at players passing by, would feel better than a beaver dungeon with bears inside.
perhaps raiding bear burrows and wolf dens would give you a rare chance to steal their cubs to train as pets. ¯\_(ツ)_/¯
p.s. also how come is this in Moot and not C&I?