There are only two beavers in all the world: Castor Fiber or the Eurasian beaver, and Castor Canadensis, our North American beaver. It’s been reported that both kinds of beavers mate for life, and new research has proven that Castor Fiber really does! Thanks to Heidi at Worth A Dam for the following link: Beavers don’t cheat on partners.
Castor Canadensis, on the other hand, pursues genetic diversity just like humans do. From the article, “The same cannot be said for their American counterparts. North American beavers are known to mate with beavers other than their bonded partners. They cheat a lot. In 2008, researchers discovered that the “father” of a pair of young was unrelated to at least one of them about half of the time.”
Science has proved it: somewhere out there, the beaver equivalent of this is happening:
We poor humans are stuck with the internet and its risk of hackers, while our little furry friends get frisky (but not risky so far as the non-existent animal std research I’ve done says) and somehow make blended families work just fine. This in spite of their hyper-acute sense of smell and ability to readily identify family members through phenotype matching (sniffing butts), even generations apart!