Beaver are very territorial and will fight frequently. If population numbers are too high the problem seems to be much worse.
I was asked to trap several farms along a small river in Eastern Washington back before the peoples republic of Snohomish and King counties deemed we would manage wildlife through the ballot box. No trapping had occurred on that river in several years. I was primarily a coyote trapper but it was coming into spring and I was done coyote trapping for the year. I thought it might open up some more good areas for me for coyote and cat and the beaver prices were fair at the time. The damage to trees in the riparian zone was tremendous.
I never before saw such bit up beaver. Nearly every one had multiple bite marks over the hips and lower back, both male and female. Some were so badly scarred up the buyers didn't want them. Fortunately castor was worth a lot that year or it would have been a loosing proposition. I took 88 beaver out of a twenty mile stretch of river. Only a handful were not scarred up. They usually came from small side drainages where they had built dams. The main river had no dams and I always felt that had some to do with the fighting as they had more territory overlap.
It took a couple seasons to thin the population to a level where the fur damage from bites was lessened significantly. It still occurred but with far less frequency.
