和漢三才図会
They are sometimes seen to be the same as the yamawaro, spoken of in Western Japan, as well as the yamako in the Wakan Sansai Zue, and as it is thought that tree spirits would cause yamabiko to occur, they are also seen to be the same as the yōkai penghou that lives in trees. In collections of yōkai depictions like the Hyakkai Zukan and the Gazu Hyakki Yagyō, the yamabiko that looks like a dog is thought to be based on the yamako or the penghou.