Thirty Siberian weasels (Mustela Sibirica) (15 males and 15 females)were sampled from Longkou Forest Farm of Tonghe in Xiaoxing’an Mountains in winter. For each individual, 5 guard hairs from the mid-back and 5 upper-hairs from the hind-claw were collected and subjected to morphological examination of scale pattern using electron scanning microscopy. All the hairs were measured for indices including hair length, medulla length, hair follicle length, hair diameter, medulla diameter,and hair root diameter using biological microscope system H6303i, and then medulla length index (ratio of medulla length to hair length) and medulla index (ratio of medulla diameter to hair diameter) were calculated. The statistical results showed that the length of guard hairs from the mid-back was 33.50±0.52 mm in males and 28.85±0.28 mm in females, the average of medulla length index was 95.36% in males and 95.16% in females, and the average of medulla index was 79.41% in male and 80.68% in females. All these indices were significantly larger than those of upper-hairs from hind-claw (P<0.05). Such morphological structure characters of guard hairs from mid-back favor heat insulation properties and those of upper-hair from hind-claw enhance the function of protection.The for the upper-hair from the hind-claw, the hair follicle length was 0.91±0.05 mm in male and 0.79±0.10 mm in female, hair root diameter was 86.0±3.7μm in male and 71.9±3.1μm in female, the ratio of the length with irregular-wave scales and regular imbricate scales to the hair length is 100% in both male and female. All these indices were significantly larger than those of guard hairs from the mid-back (P<0.05) and such morphological structure characters enhance the function of protection further. The functional differentiation between guard hairs from mid-back and upper-hairs from hind-claw make the weasels more adaptable to a cold environment with complex vegetation form.
