The long-tailed weasel, Mustela frenata, occurs in most of the United States, as well as in part of Canada and much of Mexico. The species is fairly tolerant of human presence, and is common throughout Utah. The long-tailed weasel is a habitat generalist that occurs in numerous types of habitat. Dens are located in burrows abandoned by other animals, under brush piles, or under rocks. The species is primarily nocturnal.
Females produce a single litter of one to twelve young during the spring. The diet of the long-tailed weasel is composed mainly of small rodents, although insects, birds, and other animals are also eaten. Long-tailed weasels are brown with light-colored bellies during the summer, but are almost completely white during the winter. They can be distinguished from short-tailed weasels because they are larger in size and lack a white line on the inside of each hind leg.