Though they be but little, they are fierce! The least weasel (Mustela nivalis) is the smallest species of true carnivore, coming from the order Carnivora. They are found across North America, Europe, and Asia, primarily in grasslands, pastures, and shrubby areas.
Least weasels have a long, slender body. In summer, they have a rich brown upper body and a white underside. In winter, they can be brown or all white. They lack the distinctive black tail tip of other Iowa weasels, which can be an excellent identifying feature when comparing the least weasel to other small weasels we have in Iowa. The males, which are generally bigger than the females, range from eight to nine inches long and weigh about two ounces. They are so small that they can fit into holes less than an inch in diameter.
To keep going, the least weasel must eat roughly 40 to 60 percent of its body weight every day. However, its sharp teeth and claws mean these weasels can take down animals larger than themselves. Least weasels are known to kill even more prey than they can consume — stockpiling it nearby and frequently leaving it to rot in preference to fresh meat. They primarily eat mice, but will also eat voles, insects, birds, and bird eggs. The least weasel plays an important role in reducing the rodent population, which benefits nearby agricultural fields.
Although they are considered a species of least concern by the IUCN and are judged to be secure in the nation by the U.S. federal government, they are considered a Species of Greatest Conservation Need (SGCN) in Iowa’s Wildlife Action Plan. This was determined based on the rarity of the species, the population trends, and the threats to the species. For more information on how species were selected as a SGCN, read Iowa’s Wildlife Action Plan.
Did you know?
Because of its diminutive size and ferocious nature, the least weasel plays an important role in mythology; it is the only animal capable of killing the basilisk.
To learn more about the mammals of Iowa, download or buy the Mammals of Iowa Field Guide.