What is a Weasel?
A weasel is is any small species of the genus Mustela of carnivorous mammals, to which the larger mink, ferret, and European polecat also belong. The British restrict the name to the species Mustela nivalis which in America is called "least weasel". This and a larger weasel, the ermine, occur all across northern North America, Asia, and Europe; the British refer to the ermine as stoat. The still larger long-tailed weasel, the best-known American species, occurs from southern Canada to South America.
The male is a foot and a half in length, of which the tail comprises a third. The female, about a fifth shorter, is half as heavy. Each of the three species molts into a white winter coat in the northern part of its geographic range. In summer the upper parts, tail, and outside of the legs are uniform reddish brown, and the underparts white or yellowish white. The distal fourth or more of the tail is black in all seasons except in M. nivalis. The slender body, strong flexible neck, flattened head, and short legs (each having five toes with sharp, compressed, curved claws) enable the weasel to pass through any opening that admits its head. The teeth are highly specialized for a diet of flesh. Among mammals the weasel is unsurpassed in speed of killing mice and some animals larger than itself. When given opportunity, it may kill more food than it needs immediately, but stores the excess in a larder with the same object in view as squirrels have in gathering nuts. In temperate latitudes, weasels help to check undue increases of rodents that damage cultivated crops.
The long-tailed weasel, annually about April, bears a single litter of up to nine young in an enlargement of a burrow in the ground after a gestation period of 279 (220-337) days. After months of quiescence the fertilized eggs become attached to the uterus and in less than 27 days develop into full-term embryos. Implantation of the eggs is delayed also in the ermine, but not in the least weasel.
Other species which never become white, are: in South America, the tropical weasel; in Asia, the Altai weasel, the yellow-bellied weasel, the Siberian weasel, and, in India, the backstriped weasel. Australia and most oceanic islands lack weasels. In the southern halves of South America and Africa other small mustelid mammals replace weasels.