Weasels are native to Michigan, with three distinct species inhabiting the state’s diverse landscapes. These small, elongated predators belong to the Mustela genus within the family Mustelidae. The three species found in Michigan are the Least Weasel, the Short-tailed Weasel, and the Long-tailed Weasel.
The Three Weasel Species of Michigan
The smallest and least common species is the Least Weasel (Mustela nivalis). This carnivore is occasionally encountered throughout the state, though suggested records indicate its populations are less abundant than its relatives.
The Short-tailed Weasel, also called the Ermine, is classified as Mustela erminea or Mustela richardsonii. This species is common, particularly in the northern regions of the Great Lakes area, including the Upper Peninsula. The Long-tailed Weasel (Mustela frenata) is the third species and is widely distributed.
The Long-tailed Weasel is often more tolerant of disturbed areas, meaning it may be found closer to human settlements and farmlands than the other two species. The Least Weasel remains the most elusive and is rarely trapped or sighted. All three species are active, solitary carnivores that regulate small rodent populations.
Seasonal Color Changes and Size Comparisons
Distinguishing the three species involves comparing their size and observing a key feature on their tails. The Long-tailed Weasel is the largest, measuring up to 17 inches in length. The Short-tailed Weasel is medium-sized, while the Least Weasel is the smallest, often less than 10 inches long.
Seasonal molting provides an identification clue in the northern parts of the state. In summer, all three species are brown on top with a lighter underside. The Short-tailed Weasel and the Long-tailed Weasel often molt to a pure white coat in the winter for camouflage, a phase known as “ermine.”
A defining feature that persists year-round is the black tip on the tail. Both the Long-tailed Weasel and the Short-tailed Weasel possess this black tip. The Least Weasel lacks this distinctive black tip, and its tail is proportionally much shorter than its two relatives.
Habitat and Hunting Behavior
Weasels inhabit a broad range of environments across Michigan, preferring areas with heavy cover and access to water. Long-tailed Weasels are highly adaptable and thrive in forest-field edges, open woodlands, and brushy fence lines. The Short-tailed Weasel favors diverse habitats, including wooded areas and grasslands, but typically avoids dense forests.
These mammals are specialized predators, known for their high-energy hunting style. Their primary diet consists of small rodents such as mice, voles, and shrews. Their slender, elongated bodies and short legs allow them to follow prey directly into burrows and tunnels.
Weasels have a high metabolism, requiring them to consume a significant portion of their body weight daily. This constant need for food drives their hunting activity, making them effective natural controls for rodent populations. They also prey on small birds, eggs, and insects to supplement their diet.