weasel o mustela (Mustela nivalis) is a small mammal with a long body and neck, short legs, and a small head. They are closely related to the ermine, ferrets, polecats and minks, all members of the genus Mustela and belong to the same family (Mustelidos) than badgers and otters.

The weasel is a little mammal of the mustelidae family.



Weasels are usually brown, gray, or black in color with white or yellowish markings. All weasels turn white in the winter. Lesser weasel winter hair glows bright lavender when exposed to ultraviolet light.

Weasels can vary greatly in sizes, but the most notable is the lesser weasel. It is the smallest carnivore in the world. They weigh about 25 grams and grow only 11 to 26 centimeters long.

The largest weasels include the long-tailed weasel and the tropical weasel. They grow 25 to 30 cm long and weigh 85 to 350 grams. Their tails can be 10,2 to 20,3 inches long.

On average, males are larger than females. They have long bushy tails that are about 50% of their total body length. The length of the body varies between 330 and 420 mm in males and 280 to 350 mm in females, the length of the tail is 132 to 294 mm in males and 112 to 245 mm in females.

Weasels have a small, narrow head with long whiskers. They also have short legs. The coat is made up of a short, smooth undercoat covered in shiny protective hair. They are cinnamon brown in color with white underparts that have a yellow undertone. Twice a year these weasels shed their fur, once in spring and once in fall. This process is controlled by photoperiod. The fur of the animals in the northern populations is white in winter and brown in summer, while those of the southern populations are brown all year round.

Weasels keep warm by lowering their metabolism and curling up into balls inside their burrows.


As nocturnal animals, weasels sleep during the day and are active at night. Most of an awake weasel's time consists of hunting, storing excess food, and eating. Their bodies don't store fat, so they need a constant supply of food to provide enough energy. In fact, the weasel eats at least 40 to 60 percent of its body weight every day, according to the Nature Conservancy.

Although weasels can dig their own burrows fairly quickly, they sometimes take over other animals' burrows and make them their own. They are even known to have taken over the hills by termites.

Communication and Perception

Weasels communicate with each other with visual, sound and scent signals. The females emit an attractive scent when they are ready to mate. Body language and sounds are used to communicate when weasels are facing each other.

Weasels have well-developed senses of sight, hearing, and smell, allowing them to be efficient and sensitive predators.

Role in the ecosystem

The weasel helps control the rabbit and rat population.


The most common weasel is the short-tailed weasel. It can be found in North America, Europe, and Asia, in regions as far north as the Arctic. Their homes include swamps, scrublands, hedges, alpine meadows, riparian forests, and riparian habitats.


Weasels are adaptable and live all over the world. For example, the long-tailed weasels live in North America, while the tropical one lives in South America. Japanese weasels are found in prairie, forest, village, and suburban habitats throughout Japan. Mountain weasels are found in central and eastern Asia and the African striped weasel is predictably found in Africa.

We can see the weasel in small burrows created by them or stolen.


The diet of weasels usually consists of wheel, mice and rabbits. Frogs, birds and bird eggs are also on the menu, from time to time. Their small, slender bodies allow them to squeeze into tight spots to reach small prey.

The weasel is an intelligent and versatile predator specialized in small mammals and birds. It is not afraid of attacking animals larger than itself, and it is able to adapt and survive periodic shortages because it stores its surplus killings. It is generally found "anywhere there may be prey" in New Zealand and small European countries.

To kill its prey, a weasel clings to the neck of the prey and continues to bite until the animal dies. Before killing the prey, the weasels swing back and forth and jump in a dance intended to intimidate the other animal.


weasels have several known predators. They have terrestrial and arboreal predators. Arboreal predators, or animals that live primarily in trees, include birds such as goshawks, hawks, owls and northern hawks. Terrestrial predators, or animals that live primarily on land, include other weasels, minks, foxes, coyotes, badgers, cats, domestic dogs y snakes.

Defense methods

Weasels, which are known to be quite aggressive, have various defense mechanisms against predators. As the seasons change, so does the weasel's fur coat. During the summer, their coats are brown. This helps them blend in with trees, shrubs, and forest debris. In winter, their coats often turn white to blend in with the snow. Weasels also deter predators by producing a strong musky smell from their two olfactory glands, which are located under their tails.


Weasel mating occurs in the mid-summer months. After copulation, implantation is delayed and the egg does not start to develop until March, making the total gestation time about 280 days. Birth occurs from late April to early May, and the average litter size is six.

At birth, young weasels weigh about 3 grams. They are pink in color with wrinkled skin, and they have white hair. At fourteen days, the white hair begins to thicken, and the differentiation in size makes it easy to distinguish males from females. At 36 days, young weasels are weaned and can eat food that the mother returns to the nest. They learn to kill their prey from the mother and at 56 days they are able to kill their prey by themselves. Females mate in their first summer, but males wait until the following spring.

At birth, young weasels weigh about 3 grams. They are born defenseless, with their eyes closed, and with pink, wrinkled skin and white hair. At fourteen days their white fur begins to thicken, and the size differentiation makes it easy to distinguish males from females. At 36 days, young weasels open their eyes and begin to be weaned and eat food that their mother returns to the nest. They learn to kill prey from their mother, and at 56 days they are able to kill prey on their own. Shortly after they become independent.

Shelf Life / Longevity

Many weasels die before they are one year old. However, once they have reached adulthood, they can live for several years. The life of long-tailed weasels in the wild is not well known.

State of conservation

Most weasels are on the IUCN Red List of Threatened Species as Least Concern (LC). There are some exceptions. The mountain weasel and the Japanese weasel are listed as Near Threatened (NT) because their populations have suffered a significant decline. The Colombian weasel is listed as Vulnerable (VU) due to a continuing population decline due to ongoing deforestation and has an estimated population of around 1.300 mature adults.

In New Zealand, the weasel is considered an invasive species and a threat to native wildlife. The country plans to eradicate them by 2050, according to a 2016 Live Science article.

Relationship with humans

Cats, owls, foxes and raptors will try to kill weasels, although a weasel will fight hard to defend itself. Humans have chased weasels over the years, especially in areas where pheasants and partridges are raised; game guards and farmers have always regarded weasels as a pest and caught them in large numbers. In fact, since a weasel can eat hundreds of mice in a year it should be seen as a useful friend, doing more good than harm.

Many weasels also die on the roads, but despite the dangers they face from humans, they are still fairly common and not threatened as a species.

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