Japanese weasel

The Japanese weasel, Mustela itatsi, is a carnivorous mustelid of the genus Mustela, native to the Japanese islands of Honshu, Kyushu and Shikoku and introduced to Hokkaido and the Ryukyu Islands to control rodents and to Sakhalin Island in Russia. Its closest relative is the Siberian weasel, with which it is often confused and of which it is sometimes treated as a subspecies; the two differ in the ratio of tail to head and body length, 36 to 50 percent in the Japanese weasel against more than 50 percent in the Siberian weasel, and genetic differences suggest they diverged about 1.6 to 1.7 million years ago. The species name itatsi comes from the Japanese word for weasel, itachi. It has an orange-brown coat with darker head markings that does not change colour in winter, a long slender body and tail, short legs and sharp claws, and adult males reach 35 centimetres in body length. It typically lives in mountainous or forested areas near water and eats mice, frogs, reptiles, insects and crayfish. Its population fell by 25 percent over three generations, which is why the IUCN lists it as near threatened, and Japan has banned the hunting of female Japanese weasels.