So I recently rewatched the sabaody archipelago and Bepo caught my attention. How can a bear talk? The answer is simple he shouldn't be able to. So the only thing I could think of at first was new race or its a devil fruit. It has to be either the bear bear fruit model: polar bear. Or it can be an artificial devil fruit.
I believe it could be an artificial devil fruit because one chopper should be the only animal that can talk because he ate the human human fruit. Secondly Bepo hasn't changed back into his human form if its a Zoan type. Their are reprocussions for eating a artificial devil fruit as we can see with Momonosuke. It being an artificial zoan would make a lot of sense considering Law has some shared history with Doflamingo, his own jolly rodger being an adaptation of his, also, Bepo seems embarrassed when somebody points out that he's a bear.
Lastly I thought it could be that I he was originally human but Law switched his 'soul' with a bear because his human body was diseased or something. Could be that you know "ROOM" SHAMBLES" lol.
So that is my theory let me know what you think.