The Japanese weasel (Mustela itatsi ) is a carnivorous mammal belonging to the genus Mustela in the family Mustelidae. The most closely related Mustela species is the Siberian weasel (Mustela sibirica ). Its taxonomic species name, itatsi, is based on the Japanese word for weasel, itachi (イタチ). It is native to Japan where it occurs on the islands of Honshū, Kyūshū and Shikoku. It has been introduced to Hokkaidō and the Ryukyu Islands to control rodents and has also been introduced to Sakhalin Island in Russia.
It has an orange-brown coloured fur coat with darker markings on the head and varies in size depending on its gender. They have a long slender body, a long tail, relatively short legs and sharp claws. It is often confused with the Siberian weasel which has a different ratio of tail to head and body length. Unlike other species of weasels, their coat does not change colour in winter. 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. In the wild it can live for 2 to 3 years with the highest in the range living to about 5 years. The Japanese weasel has a tail ratio of 36–50% while the Siberian weasel has a ratio greater than 50%. 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.
It is often classified as a subspecies of the Siberian weasel (M. sibirica ). The two species are very similar in appearance but differ in the ratio of tail length to head and body length. There are also genetic differences which suggest that the two diverged around 1.6–1.7 million years ago. Mitochondrial sequencing of the two species suggests that the two species diverged in the Early Pleistocene. Their ranges now overlap in western Japan where the Siberian weasel has been introduced.
Adult males of the Japanese weasel can reach 35 cm (14 in) in body length with a tail length of up to 17 cm (6.7 in). Females are smaller. The species typically occurs in mountainous or forested areas near water. Its diet includes mice, frogs, reptiles, insects and crayfish.
Japanese weasels are small carnivorous mammals native to Japan. Their fur is orange-brown with darker markings on the head. The fur on the throat is usually white in color. Females in this species are smaller than males.
Japanese weasels are native to Japan where they occur on the islands of Honshū, Kyūshū, and Shikoku. They typically live in mountainous or forested areas near water. They can also be found in grasslands, villages, and suburbs, but try to avoid big cities.
Japanese weasels are solitary and very territorial animals. They will aggressively defend their home range, especially dominant males. When cornered or very frightened, these animals produce a smelly secretion from an anal gland to scare away predators. Japanese weasels are skilfull hunters and will chase down their prey by any means. They will run down through the tunnels, climb trees, or even swim. Anywhere prey can go, they will follow. The scientific name of Japanese weasels means “to carry off mice.” When searching for mouse runways, these little animals will investigate holes and crannies in rocks, trees, and undergrowth. They use their sensitive nose and ears to locate prey. Japanese weasels are active during the day and night. They live in dens in hollow logs and tree stumps and make their hole cozy with soft feathers or grasses.
Japanese weasels are carnivores. Their diet includes mice, frogs, reptiles, insects and crayfish.
Japanese weasels are polygynous which means that one males mates with more than one female during the breeding season. These animals breed from early May to late June. After the gestation period of about 30 days, the female gives birth to 2-12 kits, but usually 5 or 6. The mother nurses her young within 8 weeks. After this time they are fully weaned and independent. Both males and females become reproductively mature at one year of age.
The native population of the Japanese weasel disappears from lowlands in the western part of Japan. The main threat is habitat loss due to residential and commercial development. These animals may also suffer from competition with the introduced Siberian weasel.
The IUCN Red List and other sources do not provide the Japanese weasel total population size. Currently, this species is classified as Near Threatened (NT) on the IUCN Red List and its numbers today are decreasing.
Due to their carnivorous diet, Japanese weasels help control populations of rodents and other small animals.
