This boys collects wood passiveley and their saddle acts like a smithy.
They have also much healt and are faster than a player and in the wild they make wood things avere you can find clemente paste, wood, rare flowers and musrooms...
But watch out, just open the inventory of it and the near castoroides will became aggressive.
They can usually can be find in the zone south 2 and in redwood rivers.
Seems to harvest more wood per hit than a mammoth, but the mammoth has better weight reduction, so just get your hairy-elephant to follow your splinter-mouse. Now admire the open plain where a proud forest once stood and laugh uncomfortably.