Weasels, badgers, skunks, and otters
(Mustelidae)
Class: Mammalia
Order: Carnivora
Family: Mustelidae
Thumbnail description
Small-to-medium carnivores characterized by long tubular shape or stocky build, short limbs, large necks, small heads, and habits that are either terrestrial or semi-aquatic
Size
4–60 in (0.1–1.5 m), 0.5–100 lb (0.25–45 kg)
Number of genera, species
25 genera; 65 species
Habitat
Forests, prairie, steppes, tundra, waterways, and seashore
Conservation status
Extinct in the Wild: 1 species; Endangered: 7 species; Vulnerable: 8 species; Lower Risk/Near Threatened: 1 species; Data Deficient: 4 species
Distribution
North and South America, Europe, Asia, Africa, and introduced in New Zealand
Evolution and systematics
The first Mustelidae appeared in the late Eocene to Oligocene from Europe and North America. Migrations to southern continents occurred first in Africa during the early Miocene, and then in South America in the Quarternary. Mustelids were among the first carnivore families to enter South America from the Panamanian land bridge, and they diversified in South America to 14 extant species.
Considered the most successful of the small carnivores, mustelids never evolved large body forms (less than 200 lbs or 100 kg), or cursorial open-country predators. Instead, mustelids are small to medium-sized, and dominate densely vegetated habitats where they occupy terrestrial, arboreal, and aquatic environments. The extant family Mustelidae includes five subfamilies: the Mustelinae (weasels, mink, polecats, and martens); the Mellivorinae (honey badgers), the Melinae (badgers), the Mephitinae (skunks), and the Lutrinae (otters). Skunks (genera Conepatus, Mephitis, and Spilogale) and stink badgers (genus Mydaus) have been suggested as belonging to their own family, the Mephitidae, based on genetic analyses. However, this classification proposed in 1997 has not yet been uniformly accepted.
Physical characteristics
The body may be either long and slender with a long tail (weasels, mink, martens, andotters), or compact with a short tail (badgers and wolverines); there are five fingers and toes with non-retractile claws. Otters have fully webbed hind feet, and most also have webbed front feet (Pteronura, Lutra, and
Lontra) but one genus has long, dexterous, and unwebbed forefeet (Aonyx). Size varies from 4–10 in (11–26 cm) in the least weasel (Mustela nivalis), which is both the smallest mustelid and the smallest carnivore, to 40–60 in (100–150 cm) in the giant otter (Pteronura brasiliensis), the largest mustelid. Depending on species, males are 10–100% larger than females. All species have strong canine teeth for capturing and killing prey.
Coloration ranges from completely white (winter coloration of least weasels) to silver (badgers Taxidea taxus and Meles meles), pale to dark brown (mink, fisher Martes pennanti, and otters), and black and white (skunks). Pelage is either uniform (mink and otters), spotted or marbled (genera Spilogale and Vormela), or striped (Gulo and Mephitis). Many species have facial stripes (skunks and badgers), or marking on the throat (American marten [Martes americana], spotted-necked otter [Lutra maculicollis], giant otter, and American mink [Mustela vison]). All species possess anal glands, and skunks (genera Conepatus, Mephitis, and Spilogale), zorillas (genus Ictonyx), and stink badgers (genus Mydaus) can spray the liquid secretions to repel aggressors.
Distribution
Mustelids occupy all continents except Antarctica. Mustelids were originally absent from Australia, but stoats (ermine or Mustela erminea), least weasels, and ferrets (Mustela putorius) were introduced to New Zealand to control rabbits.
Habitat
The Mustelidae are a diverse family that occupies a wide range of habitats from aquatic systems (otters and mink) to prairies (black-footed ferret, Mustela nigripes, and North American badger, Taxidea taxus), steppes (steppe polecat, Mustela eversmanni), treeless tundra (wolverine, Gulo gulo), and forests (most mustelids). Some species, such as striped skunk (Mephitis mephitis), tolerate humans well and abound in urban areas.
Behavior
Mustelids are mostly nocturnal, terrestrial (most species), or semi-aquatic (mink and otter), and they shelter in burrows, hollow trees, dense vegetation, rock crevices, or abandoned buildings during the day. Many species such as weasels, mink, and ferrets shelter in burrows of their prey. Most mustelids are agile tree climbers and good swimmers. One species, the sea otter (Enhydra lutris), is almost entirely aquatic.
Most species are solitary, but group living occurs in otters and European badgers (Meles meles). Some species defend exclusive territories (e.g., groups of European badgers), while others (such as striped skunk) use non-exclusive ranges that overlap with both males and females of the same species. Many species, such as otters, use their anal glands for scent marking, and skunks and stink badgers use their anal glands for defense.
Vocalizations are most developed in the Lutrinae (otters), which display a wide range of calls from purring sounds, threatening growls, and alarm calls. Skunks, zorillas (genus Ictonyx), and marbled polecats (Vormela peregusna) communicate their noxiousness to potential predator species through warning displays, whereas other mustelids may growl (badgers and wolverine) or release musk from their anal glands when threatened (weasels and mink). Most mustelids escape predation by escaping inside burrows (badgers and skunks), climbing trees (weasels, martens and wolverine), or seeking refuge in water (mink and otter). Play behavior occurs mostly in juveniles, and in adults is best known in otters sliding down muddy or snowy banks, or playing with inanimate objects in the water.
Feeding ecology and diet
Mustelids are either true carnivores (weasels, martens, and otters) or omnivores that also consume fruits and plant material (skunks, badgers, and tayra). Most species are proficient predators, killing rodent prey with a bite at the back of the neck. Small mammals such as mice and voles constitute the staple prey for most species; fish, crustaceans, and amphibians dominate the diet of otters. Most species consume reptiles opportunistically. Some species such as wolverines and fishers are opportunistic scavengers.
The long tubular shape of many mustelids allows them access to burrows of their prey. Weasels often hunt in burrows of small rodents, and American mink regularly access burrows of the muskrat (Ondatra zibethicus). Similarly, ferrets access the burrows of rabbits and hares.
Some mustelids display feeding specialization or associations with other species. The black-footed ferret depends on prairie dogs (genus Cynomys) for both food and shelter. American mink also relies heavily on muskrats as prey and use muskrat burrows and lodges as shelter. In northern Canada and the United States, the northern river otter (Lontra canadensis) uses burrows and lodges of beavers (Castor canadensis) for daily shelter and as maternity dens. Fishers probably evolved as expert predators of North American porcupines (Erethizon dorsatum). Others such as wolverines often associate with larger predators such as wolves (Canis lupus) to scavenge remains of their kills.
Reproductive biology
Only one species of mustelid, the giant otter, is monogamous; all other Mustelidae are promiscuous, meaning that individuals of both sexes will mate with numerous members of the other sex. Pair-bonds are typically short, and in some species such as striped skunk, American mink, and wolverine, ovulation is induced by copulation. Females have one litter per year, and males do not provide care for the young.
Implantation of the blastocyst into the uterine wall is delayed in many species such as wolverine, American marten, fisher, and sea otter. However, not all mustelids have delayed implantation, and many species closely related do not share this trait. For example, ermines (Mustela erminea) have delayed implantation whereas least weasels do not. Similarly, western spotted skunks (Spilogale gracilis) have delayed implantation whereas eastern spotted skunk (Spilogale putorius) do not. Delayed implantation likely offers species living in seasonal environments an advantage by allowing decoupling of mating and parturition and allowing parturition to occur at the peak availability of resources.
Conservation status
Many species are threatened because of habitat loss (e.g., black-footed ferret and many otters), or competition from other, non-native mustelids (European mink, Mustela lutreola). In contrast, several mustelids are extremely abundant and considered pests: stoats in New Zealand for depredation of native birds, skunks in North American cities for risk of rabies, and American mink in Europe for competition with the declining European mink. In 2003, 21 species of extant mustelids were listed by the IUCN. Among those, the black-footed ferret is listed as Extinct in the Wild, and seven additional species were listed as Endangered: the sea otter, the marine otter (Lontra felina), the southern river otter (Lontra provocax), the Colombian weasel (Mustela felipei), the European mink, the Indonesian mountain weasel (Mustela lutreolina), and the giant otter.
Black-footed ferrets, the most endangered of all mustelids, once occurred throughout the Great Plains in 12 states and two Canadian provinces, and possibly portions of northern Mexico. By the 1960s, the only known population of black-footed ferrets was a small colony in southwestern South Dakota, which disappeared in 1974 for unknown reasons. In 1981, a black-footed ferret was killed by a ranch dog in northwestern Wyoming, and this event led to the discovery of about 130 ferrets near Meeteetse, Wyoming. However, outbreaks of sylvatic plague and canine distemper killed nearly all of the Meeteetse population. Consequently, the remaining 18 ferrets were taken into captivity between 1985 and 1987 in an effort to save the species. Beginning in Wyoming, reintroduction efforts have since expanded to sites in Montana, South Dakota, and Arizona. The Recovery Plan for the black-footed ferret calls for the establishment of 10 or more separate, self-sustaining wild populations. In 2003, black-footed ferret still occupied less than 2% of its original range.
Significance to humans
Mustelids are of great significance to humans as furbearers. In North America, annual harvest of weasels, mink, martens, fishers, otters, and wolverines significantly contributes to the economy. In Russia, the fur trade is especially strong for sables (Martes zibellina).
Few mustelids are consumed for meat. In North America, striped skunks are an important vector of rabies, especially in the midwestern United States and Canada and the southwestern United States. In Europe, the European badger carries bovine tuberculosis, which is a significant concern to European farmers and consequently led to persecution of the badger near farms. Other mustelids also are considered pests on occasion. When near human habitations, skunks damage lawns, consume human refuse, and occasionally spray pets; weasels and ferrets may depredate domestic chickens; and otters may visit commercial fish ponds.
In Asia, species of otters such as Asian small-clawed otters (Amblonyx cinereus) and smooth-coated otters (Lutrogale perspiciallata) are tamed and used by indigenous people to catch fish. Throughout the world, ferrets are kept as pets. In North America, striped skunks also are kept as pets after their anal glands are surgically removed. Mustelids are popular in zoological gardens, especially otters, because of their playful behavior and underwater agility, and most importantly, willingness to be active during the daytime.
Species accounts
ErmineAmerican mink
Striped skunk
European otter
Wolverine
European badger
Tayra
Resources
Books:Dunstone, N. The Mink. London: Poyser Natural History, 1993.
Gittleman, J. L. Carnivore Behavior, Ecology, and Evolution. Vol. 2. Ithaca, NY: Cornell University Press, 1996.
King, C. The Natural History of Weasels and Stoats. Ithaca, NY: Cornell University Press, 1990.
Macdonald, D. W. The New Encyclopedia of Mammals. Oxford: Oxford University Press, 2001.
Neal, E., and C. Cheeseman. Badgers. London: Poyser Natural History, 1996.
Nowak, R. M. Walker's Mammals of the World. 6th ed. Baltimore: Johns Hopkins University Press, 1999.
Powell, R. A. The Fisher: Life History, Ecology and Behavior. 2nd ed. Minneapolis: University of Minnesota Press, 1993.
Wilson, D. E., and D. M. Reeder. Mammal Species of the World: A Taxonomic and Geographic Reference. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.
Periodicals:Carter, S. K., and F. C. W. Rosas. "Biology and Conservation of the Giant Otter Pteronura brasiliensis." Mammal Review 27 (1997): 1–26.
Clark, T. W., E. Anderson, C. Douglas, and M. Strickland. "Martes americana." Mammalian Species 289 (1987): 1–8.
Estes, J. A. "Enhydra lutris." Mammalian Species 133 (1980): 1–8.
Ferguson, S. H., J. A. Virgl, and S. Larivière. "Evolution of Delayed Implantation and Associated Grade Shifts in Life History Traits of North American Carnivores." Écoscience 3 (1996): 7–17.
Hillmand, C. N., and T. W. Clark. "Mustela nigripes." Mammalian Species 126 (1980): 1–3.
Larivière, S. "Aonyx capensis." Mammalian Species 671 (2001): 1–6. ——. "Ictonyx striatus." Mammalian Species 698 (2002): 1–5. ——. "Lontra felina." Mammalian Species 575 (1998): 1–5. ——. "Lontra longicaudis." Mammalian Species 609 (1999): 1–5. ——. "Lontra provocax." Mammalian Species 610 (1999): 1–4. ——. "Lutra maculicollis." Mammalian Species 712 (2002): 1–6. ——. "Mustela vison." Mammalian Species 608 (1999): 1–9. ——. "Poecilogale albinucha." Mammalian Species 681 (2001): 1–4.
Larivière, S., and F. Messier. "Aposematic Behaviour in the Striped Skunk Mephitis mephitis." Ethology 102 (1996): 986–992. ——. "Spatial Organization of a Prairie Striped Skunk Population During the Waterfowl Nesting Season." Journal of Wildlife Management 62 (1998): 199–204.
Long, C. A. "Taxidea taxus." Mammalian Species 26 (1973): 1–4.
McDonald, R. A., and S. Larivière. "Diseases and Pathogens of Mustela spp., With Special Reference to the Biological Control of Introduced Stoat Mustela erminea Populations in New Zealand." Journal of the Royal Society of New Zealand 31 (2001): 721–744.
Pasitschniak-Arts, M., and S. Larivière. "Gulo gulo." Mammalian Species 499 (1995): 1–10.
Presley, S. J. "Eira barbara." Mammalian Species 636 (2000): 1–6.
Sheffield, S. R., and C. M. King. "Mustela nivalis." Mammalian Species 454 (1994): 1–10.
Sheffield, S. R., and H. H. Thomas. "Mustela frenata." Mammalian Species 570 (1997): 1–9.
Verts, B. J., L. N. Carraway, and A. Kinlaw. "Spilogale gracilis." Mammalian Species 674 (2001): 1–10.
Wade-Smith, J., B. J. Verts. "Mephitis mephitis." Mammalian Species 173 (1982): 1–7.
Youngman, P. M. "Mustela lutreola." Mammalian Species 362 (1990): 1–3.
Other
Black-Footed Ferret Recovery Program. "Ferret Facts." [1 March 2003] .
[Article by: Serge Larivière, PhD]
