Loading profile. Please wait . . .
Mustela nivalis Linnaeus, 1766
Least Weasel
Federal Protection: No US federal protection
State Protection: No Georgia state protection
Global Rank: G5
State Rank: S1
Element Locations Tracked in Biotics: Yes
SWAP High Priority Species (SGCN): Yes
Element Occurrences (EOs) in Georgia: 2
Habitat Summary for element in Georgia: Extreme northern Georgia, meadows, fields, brushy areas,open woods
The color of the least weasel varies depending on the season. During summer season, the coat is dark brown on the dorsal side with white belly fur. During the winter, their coat is solid white, with some individuals having a black tipped tail—although this is uncommon. Least weasels are the smallest known carnivores in North America, with a total length of 180 – 215 mm (7.1 – 8.5 in), tail of 25 – 45 mm (1 – 1.8 in), hind foot length of 20 – 28 mm (0.78 – 1.1 in), ear of 10 – 15 mm (0.4 – 0.6 in), and weight of 30 – 65 g (1.1 – 2.3 oz). Males are approximately twice the size of females.
The least weasel looks similar to the ermine (Mustela erminea). The ermine, however, is larger with a longer, black-tipped tail. Long-tailed weasels (Mustela frenata) also have a similar appearance to the least weasel, but the two can be distinguished by long-tailed weasels having bigger and have longer tails (80 – 150 mm) when compared to the least weasel, overall body size being larger, and the presence of a black-tipped tail.
The least weasel can occupy a variety of habitats and commonly occurs in open areas with water. They are found in damp meadows, marshland, grasslands, river bottoms, coniferous or highland forests, and some disturbed environments like pastures. They can be found in North Georgia but are considered rare in the state.
They are considered carnivorous and specialize in small prey, primarily rodents (voles, mice, and hispid cotton rats). When prey is scarce, they will consume voles, shrews, birds, bird’s eggs, insects, and lizards. Their narrow body allows them to pursue prey into small burrows. Least weasels can only consume a few grams of food at a time, but they eat 9 – 10 times a day.
Least weasels are territorial, and the range of their territory often depends on prey abundance. The territory of a male includes the ranges of multiple females. Most individuals are solitary and use scent marking to mark the range of their territory. Least weasels do not dig their own dens, using abandoned dens of other small mammals or the den of their prey. They will line their dens with mouse fur and cache excess food in chambers of their burrows. When food is abundant, they are capable of breeding year-round. Mating season is one of the only times that adult least weasels interact, outside of territorial disputes. Females can produce 2 – 3 litters per year while the testes of males are normally only active from March to August. Males can be active all year under optimal nutritional conditions. Females do not exhibit delayed implantation, unlike other weasel species, and gestation typically lasts from 35 – 37 days before a litter of 4 – 6 kits are born. Despite reaching sexual maturity after 4 months of age, males are often unsuccessful in mating during their first year of life. Males do not participate in raising young. Their activity is described as frantic, often darting between runways and burrows and sporadically pausing to stand up and look around. Least weasels will alternate periods of activity and rest throughout the night and day. They vocalize to communicate with conspecifics. Shrill chirps, squeals, and hisses are used to express alarm or fear while females will use trills to call their young.
Least weasels can be trapped using small foothold traps or box
traps. Other, non-invasive methods that have been used include scat collection and camera trapping. Linzey and Hamed 2016 collected a significant amount of data from cat or dog-killed specimens of least weasels.
They are found in Europe, North America, Asia, and North Africa. They are typically a northern species, but recent records indicate that their range extends further southeast than previously thought. They are mostly found in the north, as they are a circumboreal species, ranging from Alaska and Canada down to Kansas and Oklahoma. Within the southeast, they are located in the Appalachian Mountain regions of North Carolina, Tennessee, and Georgia. However, numerous new records show that the least weasel is not confined to the Appalachian Mountains.
They are considered a species of least concern (IUCN) federally, however, in Georgia, the species is considered to be critically imperiled. Least weasels do not occur in large numbers in the South and have a limited range in the state. Agricultural practices and prey availability may influence population abundance in some areas. One study on southeastern populations found that domesticated cats and dogs are common threats which, if not controlled, could significantly lower population numbers.
The species is considered critically imperiled in Georgia, only having been found within the Southern Appalachian Mountain region within the northern portion of the state.
Maintaining the diversity of understory can enhance their habitat and help protect the rodent population. Creating and maintaining fencerows and other covers in agricultural areas can not only benefit this species but it’s prey as well. Management generally only applies to southeastern states. In much of its range, the species population is stable and goes unmanaged. Some states allow trapping of least weasels for fur. However, current designation might undermine population abundance due to lack of records and limited knowledge of the species distribution. This species appears to be more abundant than previously documented, and increased survey efforts are needed to better inform management decisions within the Southeast.
Allen, G. M. 1933. The least weasel a circumboreal species. Journal of Mammalogy 14:316-319.
Bangs, O. 1896. A review of the weasels of eastern North America. Biological Society of Washington. Review 3:525
Campbell, J. W., M. T. Mengak, S. B. Castleberry, and J. D. Mejia. 2010. Distribution and status of uncommon mammals in the Southern Appalachian Mountains. Southeastern Naturalist 9:275- 303.
Čanády, A. and A. Onderková. 2016. Are size, variability and allometry of the baculum in relation to body length signals of a good condition in male weasels Mustela nivalis. Zoologischer Anzeiger-A Journal of Comparative Zoology 264:29-33.
Deanesly, R. 1944. The reproductive cycle of the female weasel (Mustela nivalis). Proceedings of the Zoological Society of London. Wiley Online Library 114:339-349
Erlinge, S. 1974. Distribution, territoriality and numbers of the weasel Mustela nivalis in relation to prey abundance. Oikos 25:308-314.
Erlinge, S. 1975. Feeding habits of the weasel Mustela nivalis in relation to prey abundance. Oikos 26:378-384.
Huff, J., and E. Price. 1968. Vocalizations of the least weasel, Mustela nivalis. Journal of Mammalogy 49:548-550.
Linzey, D.W. and M. K. Hamed. 2016. Distribution of the least weasel (Mustela nivalis) in the southeastern United States. Southeastern naturalist 15(2):243-259.
Lyon, M. W. 1936. Mammals of Indiana. American Midland Naturalist 17:1-373.
Ried, F. A. 2006 Mustela nivalis least weasel. Mammals of North America. 3 rd ed. Peterson Field Guides. New York, New York.
Sundell, J., K. Norrdahl, E. Korpimäki, and I. Hanski. 2000. Functional response of the least weasel, Mustela nivalis nivalis. Oikos 90(3): 501-508.
Trani, M. K., W. M. Ford, and B. R. Chapman. 2007. The land manager’s guide to mammals of the South. The Nature Conservancy, Durham, North Carolina. 495-497.
Khaira Reed
K. Reed, Dec. 2017: original account
M. MacKnight, Dec 2018: revised content
P. Sirajuddin, April 2019: edited and updated content
S. Krueger, March 2020: edited for final