If you temd one and can't ride it because you don't have a saddle it's still very useful!!! Have it follow you while your gathering and put all of your wood, thatch, and stone on it. It has a good amount of weight, and wood weighs 20% less and stone weighs 10% less.
The way to tame these guys is to run up to one of their dams and then open it and then immediately close it (you don’t have to take anything from it, opening the dam will immediately aggravate all and any nearby beavers). Once this step has been done, you must bola the beaver (assuming only one tries to fight). I actually made a hearty mistake and bolaed the first one that came whereas I should’ve killed the second first (I was making a video, the second one got killed). Once the beaver is bolaed and separated from its mates, go behind it where it can’t hit you and hit it with a bat until you knock it out, but before doing any of these either kill jellyfish for bio-toxin for torpor (the beaver’s torpor will drain quickly) or farm a bunch of narcoberries in preparation. These guys are herbivores so you should also farm other berries besides narcoberries, or gather from the nearby forests. Keep in mind that beavers EXTREMELY slow eaters when knocked out, so patience is your weapon here.