They know longer cut the weight of wood by 1/4. They reduced it to 1/2. Like so people can see this

Wild castoroides sometimes build dams which can contain cementing paste, wood, silica pearls, rare flowers and mushrooms. But accessing the inventory of a dam will make the beavers angry so watch out!

A castoroid will collect wood from trees if it's on wandering.

If wild castoroides are penned in a small area (large tamming pen) they will create dams you can harvest for wood, cement, etc.