If you ever encounter a casteroids around, there is likely a dam nearby( it looks like a tent made of sticks). They contain lots of wood, cementing paste, and rare ingredients and resources(silica pearls, rare flowers and mushrooms). However, make sure you get rid of the beavers first, since they become aggressive if you loot the dam.
On mobile, usually they spawn on hidden lake or in the souther islets (where that hunter cave is lying down) if you see their dams get all of its resources-quit the game-and then re enter the game (it resets their aggro on you so you can farm wood without being hurt
Outstanding wood collectors. Mine has 770 weight and can carry 3K wood plus rider. Holds wood at 1/5 weight and can be used as mobile smithy. This teamed with a doed can construct a base in minutes. Must have.