Its taxonomic species name, itatsi, is based on the Japanese word for weasel, itachi (イタチ).

[3][4] It has an orange-brown coloured fur coat with darker markings on the head and varies in size depending on its gender.

[7] Average lifespan of a Japanese weasel is highly dependent on the availability of food and to a lesser extent other factors that affect its life.

The population of the Japanese weasel has seen a decline of 25% over the last 3 generations which has been used to justify its status as near threatened on the IUCN Red List.

The government of Japan has prevented the hunting of female Japanese weasels as a measure to conserve the species.

[6] Both sexes are capable of creating a smelly excretion known as musk from an anal gland used to repel predators[5] which is employed by rubbing this secretion on rocks, branches and other natural obstacles.

[7] The diet of the Japanese weasel involves a mix of animals including mice, reptiles, crayfish and frogs.

[5] The only situations that force them to leave their solitary lifestyle is cases of mating and mothers feeding their young.

Scent marks hold information that can be comprehended by other weasels about "sex, identity, social status, and breeding condition, but also the probable outcome of a confrontation.

"[11] The calls and sounds made by a Japanese weasel are varied and include trills, screeches, hisses and barks.

Once the female is tracked down, hours or days of play biting occurs before the relatively brief act of copulation.

[11] For Japanese weasels, hunting most often occurs along rivers though, at times, they enter suburban areas and grasslands to find prey.

Foxes, martens, preying birds and domestic cats hunt Japanese weasels and pose a threat to their life.

[11] In snowy areas in winter, Japanese weasels chase rodents through tunnels in the snow, using their slender bodies to their advantage.

Japanese weasels maintain this supply of excess food in their cache, and this is done at a greater importance in winter as there are days when weather prevents hunting.

Where there are chicken coops or other locations of extremely vulnerable prey, the supply of cached food can far exceed its dietary needs.

In 1932 it was also introduced to southern Sakhalin Island in Russia however there are no reliable records on the current state of the Japanese weasel's population there since 1980.

[1] The introduction of the species in some cases, especially Miyake Island has inadvertently affected population of Japanese bush warblers as they hunt eggs and chicks of the bird.

After introduction of the Japanese weasels, the survival rate of the warbler in nestling and incubation stages has been measured to be around 0.498 and 0.848.

In Japanese itachi gokko ("weasel play") defines the vicious cycle of repeating the same message.

Named kamaitachi (鎌鼬), the yokai is depicted as having long, sharp nails similar in shape to sickles.

(Y. Tanaka), writing for the British Medical Journal explains with the phenomenon that "...during thunderstorms a temporary vacuum may occur in places as a result of stray air currents, and if a part of the body comes into such a space a tear may result from the internal pressure unmodified by the action of external pressure.