What Are the Differences Between a Stoat and a Weasel?

Although stoats and weasels are commonly confused, the two are different species of land mammals. Both species belong to the Mustela genus of the Mustelid family and are believed to have evolved about 65 million years ago from the now extinct miacid. Similar in appearance, the stoat and the weasel walk low to the ground and have long, slender bodies, short legs, long tails, and long necks. Additionally, stoats and weasels can both be found in temperate climates. This article hightlights the key differences between these two animals.

The Stoat

The stoat has a reddish, brown upper fur coat and white belly during warm seasons. Its fur turns white in the winter, with the exception of the tail, which remains dark brown or black in color. The species measures between 6.7 and 12.8 inches in length, depending on sex. It is native to North America and Eurasia, where it enjoys a wide habitat range. Additionally, the stoat can be found in New Zealand, where it was introduced in the late 1800s. The stoat is not considered a subspecies of the weasel, unlike the large number of other weasel species that can be found around the world.

The Weasel

The weasel, also known as the least weasel, has several subspecies, including the Japanese weasel, Amazon weasel, European mink, Steppe polecat, Malayan weasel, and Siberian weasel. Its physical appearance include a reddish, brown upper fur coat with a white underbelly, which can be seen throughout most of its habitat. In extremely cold climates, such as high altitudes or northern regions, the weasel has a white coat. This species has an average body length of between 4.5 and 10 inches and can weigh between 1 and 8.8 ounces, depending on sex. Its native habitat is large and ranges throughout Eurasia and North Africa, as well as a smaller range in some northern parts of North America. Additionally, the weasel has been introduced to New Zealand, Crete, Malta, and other smaller islands off the coast of Africa.

Differences Between the Stoat and the Weasel

Physical Appearance

The stoat is larger in size and and weight than the weasel. While the two species have a similar appearance in terms of color, the stoat is slightly different in that it has a darker-colored tip on its tail. Additionally, the weasel has a longer tail than the stoat.

Reproductive Behavior

Both the stoat and the weasel share the same mating season, which is between April and July. The gestation period, however, is different. Female stoats carry their young for the better part of a year, about 280 days, whereas the weasel has a gestation period of just over a month, between 34 and 37 days. Additionally, both species reach sexual maturity at different ages. Both male and female weasels become sexually mature between 3 and 4 months of age. The male stoat, however, does not reach sexual maturity until around 10 or 11 months old. In contrast, the female stoat becomes fertile between 2 and 3 weeks of age, while still hairless and blind. Adult males often mate with a recently born females, which become pregnant before being weaned.

Daily Behavior and Life Expectancy

The stoat and the weasel also display slightly different behaviors. For example, the weasel is active during both daytime and nighttime hours, when it hunts for the smaller rodents like mice and voles. The stoat is also active during all hours of the day, but known to sleep at 3 to 5-hour intervals. Due to its larger size, the stoat is able to hunt slightly larger prey, like rabbits and rats. Stoats living near farms have been known to prey on chickens and their eggs.

The average lifespan of the weasel is 3 years, while that of the stoat is 10 years. Both life expectancies are based on life in the wild.

Habitat and Territory

The typical habitat of both species is relatively similar, given that each prefers open woods, hedgerows, and grasslands near water. Both the stoat and the weasel practice the same sort of territoriality, in which males have a large territory that is made up of several, smaller female territories. The dominant male protects this large territory of females from other males, particularly during breeding season. Males mark these territories by scent glands, urine, and feces. Secretions from scent glands, located around both the anal and cheek areas, are easily distinguished from one another. The stoat gives off a strong musky odor.

Additionally, both animals are similar in that they tend to seek refuge in abandoned burrows of smaller, rodent-like animals. Both are accustomed to living near human settlements as well. In North America, the two are not likely to inhabit the same regions. Their habitat preferences display only a few differences, namely that the stoat can be found at more northern latitudes and in colder habitats, like tundra. Interestingly, at these higher latitudes, the stoat species tends to be smaller in size, which is an anomaly according to Bergmann’s rule. The stoat has also adapted to higher altitudes than the weasel.

Health Problems

The health problems faced by each species are different. Tuberculosis, for example, has been reported to occur in the stoat, but not the weasel. Additionally, the stoat has been known to suffer from mange and canine distemper when in captivity. Both species may be infested with a variety of fleas, although the stoat seems to attract a larger number of flea species than the weasel. The same also applies to mite species.

Conservation Status

Both the stoat and the weasel are classified as "Least concern (LC)" by the International Union for the Conservation of Nature (IUCN) Red List. This category does not mean, however, that the species is not threatened by external forces. Habitat fragmentation due to logging and agricultural industries is an ongoing threat for both species. Additionally, the stoat and the weasel may be negatively affected by pesticides and chemical runoff of these industries, as well as any human-induced activity that results in the loss of wetlands.