I didn’t know that. Is it a territorial thing?
Mostly territorial, I think.
Kits (young beavers) are reported to be killed frequently if a pond or lake is at carrying capacity.
I suspect beavers are cannibals because I trapped hundred of muskrats when in the 1960’s before the anti-trapping craze.
Muskrats are much like small beavers, but they don’t build dams. They routinely cannibalize muskrat carcasses. I used the carcasses as bait in some cases, and caught more muskrats than other animals in those sets.
Most rodents are omnivores. I do not know for certain about beavers, whose digestive system might be a bit more specialized.