Tradition: Japanese Mythology
Alternative Names: 隠鼠, Inso, Enso, 鼴鼠,偃鼠, 鼠母, Hidden Rat, Mountain Rat
Category: Pig
The Myth
Buta Nezumi, meaning “Pig Rat,” is a mysterious beast described in Terashima Ryōan’s Wakan Sansai Zue, an illustrated encyclopedic work from the Edo period. Drawing on the Chinese medical text Bencao Gangmu, the work describes the creature as a mountain-dwelling animal that belongs to the category of beasts rather than rodents. It is said to be as large as a water buffalo and shaped like a wild boar, with a greyish-red body, legs resembling those of an elephant, and hooves like those of a donkey. Its muzzle is sharp, while its chest and the area above its tail are white.
Despite its great strength and heavy build, the creature is reportedly afraid of dogs. Its appearance is also considered an omen of water disasters. Ryōan connects this description with a passage in the Chinese Book of Liang, which mentions a mountain rat in Wa (Japan) as large as a calf. However, he notes that he has never heard of such a beast existing in Japan and wonders what the creature might actually be.
A related account appears in the Chinese supernatural collection Soushen Ji, which records the appearance of an yanshu in the eleventh month of 311. The diviner and scholar Guo Pu interpreted this apparition as a possible omen that a powerful claimant would emerge and later die by suicide. These accounts associate the mysterious animal with extraordinary events and disaster, although its precise identity remains uncertain.
Sources
“Butanezumi.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1076684724.html