Mustela Frenata - Long-Tailed Weasels...

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Geographic Range: The range of the long-tail weasel includes most of North America, extending from just north of the United States-Canadian border and south to Central America to northern South America. Long-tailed weasels have the largest distribution of any mustelid in the Western Hemisphere.

Habitat: Long-tailed weasels are found in temperate and tropical habitats in North and Central America. These habitats range from crop fields to small wooded areas to suburban areas. They are not found in deserts or thick, dense forests. Their burrows and nests are in hollow logs, rock piles, and under barns. Sometimes instead of building a new nest, long-tailed weasels take over the burrow of one of their prey.

Physical Description: Long-tail weasels have a long slender body, similar to other weasels. On average, males are larger than females. These weasels have long, bushy tails that are about 50% of their total body length. Body length varies between 330 and 420 mm in males and 280 to 350 mm in females, tail length is from 132 to 294 mm in males, and 112 to 245 mm in females. Long-tailed weasels have a small, narrow head with long whiskers. They also have short legs. The fur is composed of short, soft underfur covered by shiny guard hair. They are cinnamon brown in color with white under parts that have a yellow tinge. Twice a year these weasels shed their fur, once in the spring and again in the fall. This process is controlled by photoperiod. The coat of animals in northern populations is white in the winter and brown in the summer, while those in southern populations are brown year round.

Reproduction: Long-tailed weasels mate once each year. Young are born from April to May. Mating for long-tailed weasels occurs in the mid-summer months. After copulation, implantation is delayed and the egg does not begin to develop until March, making the total gestation time around 280 days. Birth occurs from late April to early May, and the average size of the litter is six. At birth young weasels weigh about 3 grams. They are pink with wrinkled skin, and they have white fur. At fourteen days, the white hair begins to thicken, and size differentiation makes it easy to tell males from females. At 36 days young weasels are weaned and can eat food brought back to the nest by the mother. They learn how to kill prey from the mother and by 56 days old they are able to kill prey on their own. Females mate in their first summer, but males wait until the following spring. At birth, young weasels weigh about 3 grams. They are born helpless, with eyes closed, and with pink, wrinkled skin and white fur. At fourteen days their white fur begins to thicken, and size differentiation makes it easy to tell males from females. At 36 days old young weasels eyes open and they begin to be weaned and to eat foods brought back to the nest by their mother. They learn how to kill prey from the mother, and by 56 days they are able to kill prey on their own. Soon after they become independent.

Average lifespan (captivity): 8.80 years. Many long-tailed weasels die before reaching one year old. However, once they have reached adulthood they may live for several years. The lifespan of long-tailed weasels in the wild is not well known.

Behavior: Long-tailed weasels are not social animals; the sexes live apart from each other except during the mating season. One male's home range may overlap several female home ranges, but home ranges of adults of the same sex never overlap. Weasels exhibit very aggressive behavior to intruders of their home ranges. Long-tailed weasels are quick, agile, and alert animals. They are good climbers and swimmers. Long-tailed weasels hunt their prey by picking up a scent or sound. They then follow the animal and make a quick attack. They kill their prey by a quick bite to the base of the skull. While long-tailed weasels can be active during the day, they are more active at night. These weasels are also known to be noisy animals, but the noise is usually in response to some type of disturbance.

Communication and Perception: Long-tailed weasels communicate among themselves with visual, sound, and scent cues. Females emit an attractive scent when they are ready to mate. Body language and sounds are used to communicate when weasels confront each other. Long-tailed weasels have well-developed senses of sight, hearing, and smell, which allows them to be efficient and sensitive predators.

Food Habits: Main prey are small rodents. Females, with smaller bodies, have better success in hunting small rodents because their bodies can fit inside the small rodent burrows. Males pursue larger animals, such as eastern cottontail rabbits. While mammals are the food of choice, these weasels eat a wide range of food, from birds to reptiles, and in the summer their diet includes fruits and berries.

Known Predators: Owls, coyotes, rattlesnakes.

Ecosystem Roles: Long-tailed weasels help to control populations of rodents and rabbits.

Economic Importance for Humans: Positive The pelts of long-tailed weasels were available in the fur trade but were not a popular commodity. Long-tailed weasels are good mousers and ratters, so farmers do not mind having weasels around their farms because they eliminate these pests

Newell, T. 2002. "Mustela frenata" (On-line), Animal Diversity Web. Accessed February 12, 2009 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Mustela_frenata.html.