Symbolism, Imagery, Allegory
The beaver gets pretty potent… and we're not just talking about the smell. Part of it represents Dwight's general, um, Dwightness. He deliberately runs it over with his car and then pretends it's some kind of big trophy.
That pelt's worth fifty dollars, bare minimum. (10.6)
It's not, but Dwight's supposedly knowledgeable statement helps him assert his control and power over the situation. He also makes Jack a part of it by forcing him to pick it up and put it in the car.
Then, once he gets it into the curing tub, he promptly neglects it, losing its value and distorting it into something that would probably get the health inspector out to his house in a heartbeat. The mold that grows around it kind of looks like a beaver, but it's actually pretty hideous: just like Dwight's efforts to make a "normal" family make everything dysfunctional and awful. The beaver's pretty gross by the end of it, a fitting symbol of the kind of emotional entanglement Dwight and his jerkiness have brought.