For example:
* Is it a fantasy world? Maybe beavers are magical creatures, or they're worshipped by other animals.
* Is it a post-apocalyptic world? Perhaps beavers are the only surviving mammals, and they've adapted to survive in a harsh environment.
* Is it a futuristic world? Perhaps beavers have been genetically engineered to be bigger and stronger, or they're used as laborers in some way.
Once you tell me more about your world, I can start brainstorming ideas for what beavers do in it!