Weasels belong to the same family of mammals as minks, wolverines, badgers, fishers and river otters, among others creatures. Three species of weasel inhabit North America, the long-tailed weasel, short-tailed weasel and the least weasel. Weasels are carnivores and prey mostly on insects and small rodents, though their diet may include birds and bird eggs. Active in both summer and winter, weasels prefer a constant supply of water. Compare the features of weasels to differentiate them among themselves and from their cousins whom you may encounter in the wild.
Observe the body. Weasels vary in size. The small least weasel averages 8 inches in length, and the short-tailed weasel measures 13 inches. The long-tailed weasel is the largest, running to 16 inches. Weasels are long and slender with short legs; their hind legs are only about half as long as their bodies, and the forelegs are noticeably short as well.
Check the tip of the tail. Long-tailed and short-tailed weasels have a black tip. Least weasels lack this identifying trait.
Look at the ears. A weasel's ears are rounded.
Note the color of the animal. Weasels are brown on top, with a white-yellow underside. Those inhabiting colder or mountain areas turn white in winter.
Observe the animal as it runs. Weasels have a distinctive, bounding gait, with the hind feet typically falling almost exactly where the front feet were.
Check for the presence of anal scent glands. All weasels have them.