Critter Curriculum
Long-tailed Weasel Mustela frenata The long-tailed weasel (Mustela frenata) is closely related to the short-tailed weasel (ermine), mink, river otter, pine marten and fisher. The long-tailed weasel is larger than the short-tailed weasel, but is smaller than the mink, pine marten, and fisher. This weasel is a night hunter, taking a variety of animals in trees, on the ground and from burrows below ground. The long-tailed weasel was, and still is considered, a pest to poultry farmers, as it will take eggs, young, and adult birds.

Physical Description The long-tailed weasel, like all members of the weasel family, has a small head, long slim body, long neck and short legs. It is very agile and fast when on the move, slinking along in an up and down fashion. The tail is brown with a black tip. The long-tailed weasel's coat changes color with the seasons. It is dark brown to red in the summer with lighter underparts and dark feet. In winter, it changes to a creamy-white color, which makes it harder to be seen in the snow. The long-tailed weasel can grow to be 11 to 17 inches in length and three to 16 ounces in weight. It is also known for its long, sharp and powerful canines, which allows it to be a successful predator.

Life Cycle Long-tailed weasels are polygamous, males mating with more than one female. They breed from July to August. After mating, the fertilized egg remains in limbo for seven months through a process known as delayed implantation. During this period, the embryo will not develop until the eggs are ready. This unique process allows the female to give birth when environmental conditions are at their most favorable. The female constructs a nest made of grass and leaves and lines it with rodent and rabbit fur. The fertilized egg is then implanted into the uterus wall and development of the embryo begins.

In March or early April, six to nine young are born, on average, but litter size may range from one to 12. The young have little to no fur, their eyes closed and nearly helpless. They open their eyes around 36 days and are weaned, no longer suckling, soon thereafter. The mother will then teach them hunting skills to prepare them for when they are on their own, which will occur at about two months of age. Long- tailed weasels have only one litter per year.

Females become sexually mature as early as three to four months of age and will mate their first summer. Males become sexually mature at around 15 months and mate their second summer.

Food Items Long-tailed weasels are highly carnivorous. Over half their diet consists of squirrels, burrowing rodents, mice, rabbits, snakes, frogs, and insects. They will also eat fruits, such as ripened berries, and have been known to take birds from poultry farms, when preferred food is scarce.

Long-tailed weasels take their prey by piercing and crushing the skull with their sharp canines. Even though it is small, long-tailed weasels are able to hunt prey that is much larger than they are. However, they prefer the ease of smaller victims. They will hunt in trees and underground, but most of their hunting occurs on the ground.

Habits & Habitat Long-tailed weasels are found in open woodlands, transitional areas between forests and fields, and open fields. The most common areas to find long- tailed weasels are edge areas, which are the borders between forests and open fields. This habitat provides them with the most food and cover. Weasels live in dens made from hollow logs, rock piles, or old barns in these habitats. They will also inhabit a den that it has taken over after killing the former occupant. Wherever they live, access to a permanent water source is always important.

Although largely terrestrial, these weasels are adept at climbing trees and swimming. They are known for their speed and agility. On the ground, they frequent areas occupied by small rodents and often live in the burrows of squirrels or in rotten logs, hollow stumps, and under tree roots.

Long-tailed weasels are active both day and night, but more so during the night. Both males and females can be extremely aggressive. Males are territorial and, when defending their territory, often puff themselves up in a threatening display. They sometimes scream and bark to scare off intruders.

They remain active in the winter. Abundance Long-tailed weasels can be found throughout Vermont. They are more common in areas where preferred habitat is abundant, such as open woodlands and transitional areas between forests and fields.

History The long-tailed weasel has proven itself as an adaptable species in Vermont. As the landscape changed over the last 150 years from agriculture to forests, the long-tailed weasel population has persisted. Today, it is an important predator in our ecological community.

Resource Utilization Long-tailed weasels are an important predator species in our wildlife community. They can play a vital role in controlling populations of rodents that might otherwise damage agricultural crops or transmit disease. Trapping is legal, but due to low trapper effort, the annual harvest is almost negligible.

Management Efforts Continued monitoring is conducted to ensure that the long- tailed weasel population remains healthy and abundant in Vermont.