Mustela sibirica
Siberian weasel

Mustela sibirica can be found throughout eastern Asia, north to the Sea of Okhotsk, and south to Kwangtung in China. In the south they range west to the edge of Tibet and the Gobi Desert, and north of the Gobi extending to European Russia. They have also been introduced to many of the islands of Japan. (Xu et al.,1995; Honacki et al., 1982; Tate and Hamiliton, 1947)

In Taiwan, Siberian weasels are mainly found in secondary forests at elevations of 1400-1700m. Siberian weasels can also be found, in less abundance, in primary forest and coniferous plantations. The preferred terrain for this species varies from ridges with 13 degree slopes to areas near water with slopes up to 37 degrees. (Hai-Yin, 1999)

M. sibirica is pale brown on the back, gradually changing to a paler, yellowish brown below. The tip of the tail may be a darker shade of brown than the rest, but is not black. These animals measure 48 to 66cm from head to tail, with tail length from 18 to 25.5cm. The foot measures from 6 to 7.2cm. Average adult body weight is 57g with males slightly larger than females. (Tate and Hamilton, 1947; Gittlemen, 1985)

A study of wild populations in Japan showed that the average longevity of Siberian weasels was about 2.1 years. The oldest weasels were found to be between 5 and 6 years old. One captive M. sibirica lived to be 8 years and 10 months old. (Mayagi et al., 1983)

Siberian weasels are nocturnal and crepuscular. With the exception of the association between mothers and their young, these animals are solitary. They maintain territories, although they are known to migrate in times of food shortages. They have been observed moving up to 8 km in a single night. (Nowak, 1999)

Siberian weasels, like many other members of the genus Mustela, are efficient and ferocious predators. They feed on rice-field rats (Rattus argentiventer) in the coastal areas of southern China. In parts of their range (Nakdong Estuary, Republic of Korea) Siberian weasels may feed on little terns (Sterna albifrons) and their eggs.

In the subtropical forests of Taiwan M. sibirica was found to feed on a variety of small mammals (shrews, rats, mice) and to switch to a more invertebrate diet (including beetles, grubs and other invertebrates) when small mammal populations were low.

They store prey for later consumption, especially for eating during the winter. In times of food shortages, they have been known to make mass migrations

(Xu et al., 1995; Soon-Bok et al., 1998; Wu, 1999; Nowak, 1999)

Siberian weasels, like their relatives, are capable of standing up to attackers that are larger than themselves. The primary predators of weasels are probably large raptors, such as owls and hawks.

Siberian weasels play an important role in controlling rodent and other small mammal populations in the ecosystems in which they live.

Siberian weasels sometimes take domestic fowl.

As predators, these weasels perform an obvious function in controlling small rodent population. However, in recent years researchers have found the anal-gland secretions of M. sibirica cause rice-field rats (Rattus argentiventer) to go into self-anointing behavior. As a result, Siberian weasels are being introduced into agricultural areas to help control populations of these rats. (Xu, 1995; Zhongjian et al., 1995) They are also important in the fur trade (Nowak, 1999).

M. sibirica is on CITES Appendix III for populations in India.

Recent studies of mitochondral DNA support the hypothesis that Mustela itatsi and Mustela sibirica (once thought to be the same species) are actually two distinct species. This same study has also revealed that a population of M. sibirica that was indroduced to Japan from Korea may be going through a genetic bottleneck. (Naoko et al., 1998)