mustelid, (family Mustelidae), any of about 62 species of ferrets, polecats, badgers, martens, otters, the wolverine, and other members of the weasel family. Historically, skunks were also included in Mustelidae, but genetic analyses suggest that they belong to a separate family of their own (Mephitidae). Mustelids are fur-bearing carnivores that inhabit terrestrial and aquatic regions throughout the world, except Australia, Antarctica, and most oceanic islands. Many mustelids, such as the American mink (Neovison vison), are trapped or raised commercially for their pelts.

Natural history

Most mustelids are fairly small. The least weasel (Mustela nivalis), which measures 11–26 cm (4–10 inches) long and weighs only 25 grams (0.9 ounce), is the smallest. The largest is the sea otter (Enhydra lutris) at about 1 meter (3.3 feet) long and a weight of 25–45 kg (55–99 pounds). The largest terrestrial mustelid is the wolverine (Gulo gulo), found in the northern United States and throughout Canada and northern Europe. It measures up to 1.2 meters in length and can weigh up to 20 kg (44 pounds) or more.

Many mustelids have a long tube-shaped body, short legs, and a strong thick neck with a small head. All possess well-developed anal scent glands. The five digits on each foot are equipped with sharp nonretractile claws. Males are usually larger than females; among some weasels, males are almost twice as large. A tubular body does not retain heat as well as a stockier body of the same weight and is therefore associated with higher metabolism. As a result, mustelids are very active and inquisitive in their constant search for prey.

Britannica Quiz

Wild Words from the Animal Kingdom Vocabulary Quiz

Most mustelids are strictly carnivorous, but a few include plant matter, mostly fruits or berries, in their diet. Dentition is characterized by strong canine teeth and sharp molars and premolars. Some mustelids have specialized diets. Clawless otters (genus Aonyx) specialize in crustaceans (especially crabs) and mollusks, whereas other otters (genus Lutra) are primarily fish eaters. Among the weasels (genus Mustela), specialization occurs even between the sexes, such that males, owing to their larger size, consume larger prey than females do.

Mustelids are mostly solitary except for Eurasian badgers (Meles meles), sea otters, and some northern river otters (Lontra canadensis). In solitary species, association between males and females during the mating season is brief. Mating occurs mostly in the spring, and, in many species, ovulation is induced during copulation. Delayed implantation of the fertilized egg occurs in many mustelids. Females raise the young alone. Only the least weasel produces two litters yearly; other species produce annually. In most mustelids, the young become sexually mature at about 10 months of age. Mustelids evolved from North American and Eurasian forms in the early Oligocene Epoch, some 30 million years ago.

Classification

• Family Mustelidae

  62 species in 23 genera belonging to 8 subfamilies, found worldwide except Australia and Antarctica.

  • Subfamily Guloninae

    11 species.

    • Genus Eira (tayra)

      1 species.

    • Genus Gulo (wolverine)

      1 species.

    • Genus Martes (martens)

      8 species.

    • Genus Pekania (fisher)

      1 species.

  • Subfamily Helictidinae

    5 species.

    • Genus Melogale(ferret-badgers)

      5 species.

  • Subfamily Ictonychinae

    7 species.

    • Genus Galictis (grisons)

      2 species.

    • Genus Ictonyx (striped polecat and zorilla)

      2 species.

    • Genus Lyncodon (Patagonian weasel)

      1 species.

    • Genus Poecilogale (African striped weasel)

      1 species.

    • Genus Vormela (marbled polecat)

      1 species.

  • Subfamily Lutrinae (otters)

    12 species.

    • Genus Amblonyx (small-clawed otter)

      1 species found in South and Southeast Asia and in New Guinea.

    • Genus Aonyx (small-clawed or clawless otter)

      1 species found in sub-Saharan Africa.

    • Genus Enhydra (sea otter)

      1 species found in North America.

    • Genus Hydrictis (spotted-necked otter)

      1 species found in South America.

    • Genus Lontra (river otters)

      4 species found in the Americas.

    • Genus Lutra

      2 species found in Africa and Eurasia.

    • Genus Lutrogale (smooth-coated otter)

      1 species found in southern Asia.

    • Genus Pteronura (giant otter)

      1 species found in South America.

  • Subfamily Melinae (badgers)

    7 species.

    • Genus Arctonyx (hog badgers)

      3 species.

    • Genus Meles (Eurasian badgers)

      4 species.

  • Subfamily Mellivorinae

    1 species.

    • Genus Mellivora (ratel, or honey badger)

      1 species.

  • Subfamily Mustelinae

    18 species.

    • Genus Mustela (weasels, including the mink, ermine, and ferret)

      14 species.

    • Genus Neovison or Neogale (minks)

      4 species.

  • Subfamily Taxidiinae

    1 species.

    • Genus Taxidea (American badger)

      1 species.