Mustelids vary greatly in size and behaviour. The smaller variants of theleast weasel can be under 20 cm (8 in) in length, while thegiant otter ofAmazonian South America can measure up to 1.7 m (5 ft 7 in) andsea otters can exceed 45 kg (99 lb) in weight.Wolverines can crush bones as thick as the femur of amoose to get at themarrow, and have been seen attempting to drivebears away from their kills. The sea otter uses rocks to break open shellfish to eat.Martens are largelyarboreal, whileEuropean badgers dig extensive tunnel networks, calledsetts. Only one mustelid has been domesticated; theferret.Tayra are also kept as pets (although they require aDangerous Wild Animals licence in the UK), or as working animals for hunting or vermin control. Others have been important in thefur trade—themink is oftenraised for its fur.
Being one of the most species-rich families in the order Carnivora, the family Mustelidae also is one of the oldest. Mustelid-like forms first appeared about 40 million years ago (Mya), roughly coinciding with the appearance ofrodents. The common ancestor of modern mustelids appeared about 18 Mya.[4]
Within a large range of variation, the mustelids exhibit some common characteristics. They are typically small animals with elongated bodies, short legs, short skulls, short, round ears, and thick fur.[5] Mustelids' long, slender body structure is adapted to three main lifestyles: terrestrial, arboreal, and aquatic/semi-aquatic.[6] They exhibit digitigrade or plantigrade locomotion, with five toes on each foot, enabling them to move in different ways (i.e. digging, climbing, swimming).[7] Most mustelids are solitary, nocturnal animals, and are active year-round.[8] Their dense fur, often serving as natural camouflage, undergoes seasonal changes to help them adjust to varying environmental conditions.[6]
Mustelids exhibit sexual dimorphism, with males being larger than females, but degree varies between species as well as geographically within species.[6] Male mustelids have a bifurcated penis and baculum.[7] Most mustelid reproduction involvesembryonic diapause.[10] Theembryo does not immediately implant in theuterus, but remains dormant for some time. No development takes place as long as the embryo remains unattached to the uterine lining. As a result, the normal gestation period is extended, sometimes up to a year. This allows the young to be born under favourable environmental conditions. Reproduction has a large energy cost, so it is to a female's benefit to have available food and mild weather. The young are more likely to survive if birth occurs after previous offspring have beenweaned.
Mustelids are predominantly carnivorous, although some eat vegetable matter at times. While not all mustelids share an identicaldentition, they all possess teeth adapted for eating flesh, including the presence of shearingcarnassials. One characteristic trait is a meat-shearing upper-back molar that is rotated 90°, towards the inside of the mouth.[11][12] With variation between species, the most commondental formula is3.1.3.13.1.3.2.[8]
Thefisher, tayra, and martens are partially arboreal, while badgers arefossorial. A number of mustelids have aquatic lifestyles, ranging fromsemiaquatic minks andriver otters to thefully aquatic sea otter, which is one of the few nonprimate mammals known touse tools while foraging. It uses "anvil" stones to crack open the shellfish that form a significant part of its diet. It is a "keystone species", keeping its prey populations in balance so some do not outcompete the others and destroy thekelp in which they live.
Theblack-footed ferret is entirely dependent on another keystone species, theprairie dog. A family of four ferrets eats 250 prairie dogs in a year; this requires a stable population of prairie dogs from an area of some 500 acres (2.0 km2).
Skunks were previously included as a subfamily of the mustelids, but DNA research placed them in their own separate family (Mephitidae).[13]Mongooses bear a striking resemblance to many mustelids, but belong to a distinctly differentsuborder—theFeliformia (all those carnivores sharing more recent origins with thecats) and not theCaniformia (those sharing more recent origins with thedogs). Because mongooses and mustelids occupy similarecological niches,convergent evolution has led to similarity in form and behavior.[14]
Several mustelids, including the mink, thesable (a type of marten), and thestoat (ermine), possessfurs that are considered beautiful and valuable, so have been hunted since prehistoric times. From the early Middle Ages, thetrade in furs was of great economic importance for northern and eastern European nations with large native populations of fur-bearing mustelids, and was a major economic impetus behind Russian expansion intoSiberia and French and English expansion in North America. In recent centuriesfur farming, notably of mink, has also become widespread and provides the majority of the fur brought to market.
One species, thesea mink (Neogale macrodon) of New England and Canada, was driven toextinction by fur trappers. Its appearance and habits are almost unknown today because no complete specimens can be found and no systematic contemporary studies were conducted.
Thesea otter, which has the densest fur of any animal,[15] narrowly escaped the fate of the sea mink. The discovery of large populations in the North Pacific was the major economic driving force behind Russian expansion intoKamchatka, theAleutian Islands, andAlaska, as well as a cause for conflict withJapan and foreign hunters in theKuril Islands. Together with widespread hunting in California and British Columbia, the species was brought to the brink of extinction until an international moratorium came into effect in 1911.
Mustelidae is a subfamily inMusteloidia, a superfamily of mammals that is united by shared skull and teeth characteristics. Mustelids are believed to have separated from their next closest related family, Procyonidae, around 29 million years ago.[17] The oldest known mustelid from North America isCorumictis wolsani from the early and late Oligocene (early and lateArikareean, Ar1–Ar3) ofOregon.[1] Middle OligoceneMustelictis from Europe might be a mustelid, as well.[1] Other early fossils of the mustelids were dated at the end of the Oligocene to the beginning of the Miocene. Which of these forms are Mustelidae ancestors and which should be considered the first mustelids is unclear.[18]
The fossil record indicates that mustelids appeared in the late Oligocene period (33 Mya) in Eurasia and migrated to every continent except Antarctica and Australia (all the continents that were connected during or since the early Miocene). They reached the Americas via theBering land bridge.
Multigene phylogenies constructed by Koepfli et al. (2008)[24] and Law et al. (2018)[4] found that Mustelidae comprises eight living subfamilies. The early mustelids appear to have undergone two rapid bursts of diversification in Eurasia, with the resulting species spreading to other continents only later.[24]
Phylogenetic tree of Mustelidae. Contains 53 of the 79 putative mustelid species.[4]
Time-calibrated tree of Mustelidae showing divergence times between lineages. Split times include: 28.8 million years (Ma) for mustelids vs. procyonids; 17.8 Ma for Taxidiinae; 15.5 Ma for Mellivorinae; 14.8 Ma for Melinae; 14.0 Ma for Guloninae + Helictidinae; 11.5 Ma for Guloninae + Naquinae vs. Helictidinae; 12.0 Ma for Ictonychinae; 11.6 Ma for Lutrinae vs. Mustelinae.[4]
Mustelid species diversity is often attributed to an adaptive radiation coinciding with themid-Miocene climate transition. Contrary to expectations, Law et al. (2018)[4] found no evidence for rapid bursts of lineage diversification at the origin of the Mustelidae, and further analyses of lineage diversification rates using molecular and fossil-based methods did not find associations between rates of lineage diversification and mid-Miocene climate transition as previously hypothesized.
^abcMacdonald, David W.; Newman, Christopher; Harrington, L. A., eds. (2018).Biology and conservation of musteloids (First ed.). Oxford: Oxford University Press.ISBN978-0-19-182051-9.
^Taylor, Ken (1994)."Wolverine".Wildlife Notebook Series. Alaska Department of Fish & Game.Archived from the original on 6 December 2006. Retrieved21 January 2007.
^Yochem, Pamela K.; Stewart, Brent S. (2002)."Hair and Fur". In Perrin, William F.; Würsig, Bernd;Thewissen, J. G. M. (eds.).Encyclopedia of Marine Mammals. San Diego: Academic Press. p. 548. "Sea otters have the densest fur of any mammal, with approximately130,000 hairs/cm2, about twice as dense as that of northern fur seals (Callorhinus ursinus)."
^Valenciano, A.; Jiangzuo, Q.; et al. (March 2019). "First Record ofHoplictis (Carnivora, Mustelidae) in East Asia from the Miocene of the Ulungur River Area, Xinjiang, Northwest China".Acta Geologica Sinica.93 (2):251–264.Bibcode:2019AcGlS..93..251V.doi:10.1111/1755-6724.13820.S2CID133900941.
^Morlo, M.; LeMaitre, A.; et al. (November 2019). "First record of the mustelid Trochictis (Carnivora, Mammalia) from the early Late Miocene (MN 9/10) of Germany and a re-appraisal of the genus Trochictis".Historical Biology.33 (8):1183–1195.doi:10.1080/08912963.2019.1683172.S2CID209607263.
![Phylogenetic tree of Mustelidae. Contains 53 of the 79 putative mustelid species.[4]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aMustelidaePhylogeneticTree_(edited).jpg)
![Time-calibrated tree of Mustelidae showing divergence times between lineages. Split times include: 28.8 million years (Ma) for mustelids vs. procyonids; 17.8 Ma for Taxidiinae; 15.5 Ma for Mellivorinae; 14.8 Ma for Melinae; 14.0 Ma for Guloninae + Helictidinae; 11.5 Ma for Guloninae + Naquinae vs. Helictidinae; 12.0 Ma for Ictonychinae; 11.6 Ma for Lutrinae vs. Mustelinae.[4]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aMustelidae_timetree_(edited).jpg)
