Weasels are small, active predators. These mammals, belonging to the genus Mustela, are found across various Northern Hemisphere regions, including North America, Europe, and Asia. Their reputation for quick, darting movements aligns with their physical characteristics, which are finely tuned for hunting small prey in confined spaces.
General Appearance and Body Structure
Weasels possess a distinctive body structure characterized by a long, slender, and flexible torso. This elongated shape, combined with short legs, allows them to navigate and pursue prey directly into their burrows and through narrow crevices. Their bodies do not bulge at the abdomen, maintaining a streamlined profile for underground hunting. This body type also contributes to their characteristic rolling gait, where their bodies bend upward as they move.
The size of weasels varies among species, but they are generally small carnivores. The least weasel (Mustela nivalis) is considered the smallest living carnivore, measuring about 4 to 10 inches (11 to 26 cm) in length. Larger species, such as the long-tailed weasel (Mustela frenata), can range from 11 to 16.5 inches (28 to 42 cm) in body length. Males are typically larger than females. Their strong, thick necks are connected to small, flattened heads.
Key Identifying Features
Weasels are typically recognized by their fur coloration, which often features brown or reddish-brown upperparts contrasted sharply with white or cream-colored underparts. The line separating these two distinct colors can be straight or, in some species like the least weasel, have an undulating, wavy pattern. Their fur is short but dense.
Many weasel species exhibit seasonal changes in their coat color, particularly those in northern latitudes. As winter approaches and daylight hours shorten, their brown summer fur can transition to an all-white coat, providing camouflage against snowy landscapes. This adaptation is primarily triggered by changes in day length rather than temperature. Even when turning white, some species, like the long-tailed weasel and short-tailed weasel, retain a distinct black tip on their tail, which can serve as a distraction for predators.
Beyond their fur, weasels have small, pointed heads with small, rounded ears that lie almost flattened against the skull. Their eyes are typically small and black. Weasels possess a relatively short tail compared to their body length. For example, the tail of a least weasel may be 1.2 to 3.4 inches (3 to 8.7 cm) long, while a long-tailed weasel’s tail can be 3.1 to 6.3 inches (8 to 16 cm). They also have five toes on each foot, tipped with sharp, curved claws that are not retractable.