Least Weasel - Physical Description

Physical Description

The least weasel has a thin, greatly elongated and extremely flexible body with a small, yet elongated, blunt-muzzled head which is no thicker than the neck. The eyes are large, bulging and dark coloured. The legs and tail are relatively short, the latter constituting less than half its body length. The feet are armed with sharp, dark claws, and the soles are heavily haired. The skull, especially that of the small rixosa group, has an infantile appearance when compared with that of other members of the genus Mustela (in particular, the stoat and kolonok). This is expressed in the relatively large size of the cranium and shortened facial region. The skull is, overall, similar to that of the stoat, but smaller, though the skulls of large male weasels tend to overlap in size with those of small female stoats. It usually has 4 pairs of nipples, but these are only visible in females. The baculum is short (16–20 mm), with a thick, straight shaft. Fat is deposited along the spine, kidneys, gut mesentries and around the limbs. The least weasel has muscular anal glands under the tail, which measure 7 x 5 mm, and contain sulphurous volatiles, including thietanes and dithiacyclopentanes. The smell and chemical composition of these chemicals are distinct from those of the stoat. The least weasel moves by jumping, the distance between the tracks of the fore and hind limbs being 18–35 cm.

Dimensions vary geographically, to an extent rarely found among other mammals. Least weasels of the vulgaris group, for example, may outweigh the smaller races by almost four times. In some large subspecies, the male may be 1.5 times longer than the female. Variations in tail length are also variable, constituting from 13-30% of the length of the body. Average body length in males is 130–260 mm, while females average 114–204 mm. The tail measures 12–87 mm in males and 17–60 mm in females. Males weigh 36-250 grams, while females weigh 29.5-117 grams.

The winter fur is dense, but short and closely fitting. In northern subspecies, the fur is soft and silky, but coarse in southern forms. The summer fur is very short, sparser and rougher. The upper parts in the summer fur are dark, but vary geographically from dark-tawny or dark-chocolate to light pale tawny or sandy. The lower parts, including the lower jaw and inner sides of the legs, are white. The dividing line between the dark upper and light lower parts is straight, but sometimes forms an irregular line. In winter, the fur is pure white, and only exhibits black hairs in rare circumstances.