About Mustela eversmanii Lesson, 1827
Steppe polecat (Mustela eversmanii Lesson, 1827) is very similar to the European polecat in general appearance, body proportions and habits, but its body appears somewhat more elongated because it has shorter guard hairs. Its tail is short, making up one-third of its total body length. Compared to the European polecat, the steppe polecat has a heavier, more massive skull, with more widely spaced zygomatic arches and more strongly developed projections, especially the sagittal crest. It closely resembles the North American black-footed ferret; the only notable differences are that the steppe polecat has much longer, softer fur, shorter ears, and a shorter postmolar extension of the palate. Steppe polecats have four pairs of teats and well-developed anal glands that produce a strong-smelling liquid sprayed for self-defense. Adult males have a body length of 320–562 mm (12.6–22.1 in), while adult females measure 290–520 mm (11–20 in). Male tail length ranges from 80–183 mm (3.1–7.2 in), and female tail length ranges from 70–180 mm (2.8–7.1 in). Males in Siberia can weigh up to 2.0 kg (4.5 lbs), and females weigh up to 1.4 kg (3.0 lbs). One exceptionally large steppe polecat from Semirechye had a body length of roughly 775 mm (30.5 in). Overall, giant individuals are more common in steppe polecats than in European polecats, and these large specimens occur mostly in western Siberia, where steppe polecats likely hybridize with Siberian weasels. The steppe polecat’s winter fur is soft and long, with short, dense underfur and long, sparse guard hairs. Generally, its fur is shorter and less thick than the European polecat’s fur. Guard hairs are most developed on the lower back, but are still sparser than those of the European polecat. Unlike the European polecat, the steppe polecat’s guard hairs never fully cover its underfur. The base color of winter fur is a very light yellowish or whitish-yellowish shade. Guard hair tips are blackish-brown or brown, creating a frosting effect over the yellow underfur. This effect is more prominent on the middle and lower back, where guard hairs are denser and longer. Guard hairs on the upper back, flanks, area between the shoulders, and along the upper neck are extremely short, making these regions lighter in color than the posterior part of the body. The head is piebald: the area around the eyes and the upper side of the nose are covered by a brownish mask. A white band runs across the head from cheek to cheek behind the mask. A small brownish patch usually sits in front of each ear. The ears are entirely white, and the throat is yellowish-white or nearly white. In some cases, the entire head is white. The lower neck is dark blackish-brown or brown, while the chest and forelegs are black or blackish-brown. The abdomen is a light yellowish-straw color. The groin matches the forelegs in color. The base of the tail is light, and the tip is dark brown. The summer coat is shorter and coarser than winter fur, less dense and less close-fitting, and has a more prominent ochreous or reddish tone. The overall head color is darker in summer than in winter, with stronger contrast between dark and white markings. Steppe polecats range from Central and Eastern Europe in the west, through southern Russia, northern Georgia, Kazakhstan, Turkmenistan, Uzbekistan, Tajikistan, and Kyrgyzstan, to Mongolia and northern and western China. In 2014, the species was recorded at 5,050 m (16,570 ft) elevation in Upper Mustang, Annapurna Conservation Area, Nepal. In captive individuals, mating has been observed from early March to the end of March. At the Moscow Zoo, seven instances of mating were recorded between 9 April and 9 June. Estrus symptoms appear around 12–13 March, and continue developing over two to three weeks. After mating, these symptoms disappear within three to four weeks. The mating season falls in March for steppe polecats in western Siberia, while in Transbaikalia it extends to the end of May. Copulation lasts between 20 minutes and three hours. If a female does not produce a litter, or if the litter dies early, estrus may last longer or reoccur. Typically, steppe polecats mate once per year and produce one litter annually. Gestation lasts 36–43 days. Placentation occurs two weeks after mating, with the blastocyst stage lasting seven to eight days. Litters usually contain three to six kits, though litters as large as 18 have been recorded. Newborn kits are blind and naked, with pale pink skin and a membrane covering their ears. At birth, they measure 6.5–7 cm (2.6–2.8 in) in length and weigh 4.5 grams (0.16 oz), though kits born at the Moscow Zoo weighed 10 grams (0.35 oz). Newborn weight generally depends on litter size. A thin layer of white underfur grows on the body after three days. By this point, body length has doubled, and weight has increased six-fold to up to 33 grams (1.2 oz). Milk teeth erupt around this same time, and the feet begin to darken. By the 20th day, kits have darkened in color and weigh 70–72 grams (2.5–2.5 oz). Their eyes open between 28 and 34 days, and kits become more active, even attempting to tear apart prey while still nursing. At one month old, kits measure 190 mm (7.5 in) in length and weigh 138 g (4.9 oz). By 45 days old, they can hunt young ground squirrels, and start targeting adult ground squirrels by the time they reach 60 days old. Kits stay in the family burrow for 2.0–2.5 months. They begin dispersing in July or later, reach sexual maturity at 10 months old, and become fully mature adults at two years old.
