I have tamed two of these dudes so far, and one is called Goldfur and her fur is golden and I have another one called Graystripe because of his gray stripe. All you have to do to tame these guys is: find one on land (like where I found graystripe and goldfur) go very close to the giant beaver if you have bad aim and then bola the beaver, use tranq arrows or club, once it’s knocked out feed it mejoberrys or just any berrys and you might have to punch it or just do something to keep it knocked out. And then soon you will have a pet castoroides. And when you get one of these dudes BRING HIM/HER HOME STRAIGHT AWAY, OR ELSE YOU MIGHT RUN INTO A HIGH LEVEL CARNIVORE AND YOU WILL HAVE TO WATCH YOUR NEW FRIEND DIE. (That happened to my first castoroides, who had no name because I just got him) And I’m around level fifty so don’t feel sad that you can’t tame one of these giant beavers because your only level forty. These beavers will be your best friend.