American Mink

(Neovison vison)

Photo by Needsmoreritalin

American mink are native to North America, but can be found introduced in several continents. American mink and their recently extinct cousin the sea mink († Neovison macrodon) are generally considered the only “true” species of mink. This is because the supposed European mink is actually a semi-aquatic polecat, being much closer related to the European polecat and Siberian weasel.(1)(2) The American mink was once considered a weasel of the genus Mustela, but in 1999 the Latin name was changed to Neovison.(3)

Appearance

Relatively slim, but the face in particular has blunt and boxy features. The eyes are small and the nose is large in comparison, emphasized by prominent whisker pads that gives the mink an otter-like quality. The long and dense fur hides most the ears and emphasizes the robust anatomy. Their paws are partially webbed and more sparsely furred than the rest of the body, supporting their semi-aquatic nature.

The fur is usually chocolate- to reddish brown in colour, decorated with patches on the chin, chest, and throat. It’s smooth and thick in structure, with oily guard hairs that waterproof the mink’s coat. The summer coat is generally shorter, sparser and duller than the winter coat.

Winter coat: Longer, denser, silkier and much darker.

Habitat

The American mink dwells in forested areas near rivers, streams, lakes, ponds and marshes.

Behaviour (non-feral)

American mink are mostly nocturnal and solitary animals, with males being particularly intolerant of one another. There is however, extensive overlap in territories between the opposite sex. Their home ranges are usually 1–6 kilometres (0.62–3.73 miles) long, with male territories larger than females’.(4) Like most mustelids, American mink use their enlarged anal glands to mark the boundaries of their territories.

American mink will dig their burrows in river banks, lakes and streams; also holes under logs, tree stumps, or in roots and hollow trees. They will at times use abandoned dens of other mammals, such as badgers, skunks and muskrats. Sometimes dens located in rock crevices, drains, and nooks under stone piles and bridges are also chosen.(5)

The burrows that they dig themselves are usually four inches in diameter, and may continue along for 300–370 cm (10–12 feet) at a depth of 61–91 cm (2–3 feet).(6) These burrows are characterized by numerous entrances and twisting passages, consisting of one to eight exits. They will occasionally line the interior of their den with dried grass and leaves, or fur from past prey.(7) American mink are also excellent swimmers, and have been reported to swim 30 meters (100 feet) underwater, and dive to depths of 5 meters (16 feet).(8)

Reproduction

Mating season ranges from February in the southern range, and to April in the north, and lasts for three weeks. The mating process is aggressive, with males typically biting the nape of the female’s neck and pinning her with his forepaws. Mating can last anywhere from 10 minutes to four hours. Once a female is impregnated, the gestation period last from 40 to 75 days.(9)

The young are born from April to June, with litters consisting of four kits on average. The kits are blind at birth. They depend on their mother’s milk for five weeks, and begin hunting after eight weeks of age. They do not become fully independent until autumn. They reach sexual maturity the following spring at about 10 months old.(9)

Diet

The diet of American mink varies by season and region. During the summer they consume crayfish and small frogs, as well as smaller mammals such as shrews, rabbits, mice, and muskrats. Fish, ducks and other water fowl provide additional food choices.(10)

In British Isles, European rabbits are common summer prey, while European hares are preyed on occasionally.(10) In South America’s Cape Horn Biosphere Reserve, several native and exotic mammals are the American mink’s main prey.(11)

Predators

Although adult American mink can generally defend themselves, their young can fall prey to bobcats, coyotes, wolves and birds of prey.(7)

Surplus killing

The American mink will occasionally exhibit surplus killing behaviour when presented with an abundance of food. However, most surplus food is carried to a den to be cached for later consumption.(12) This is more beneficial during the winter months when carcasses do not spoil as quickly. Similar to how we humans tend to hoard more food than we can eat during times of uncertainty, it is possible that surplus killing in the American mink is an evolutionary response to unpredictable food resources;(13) never knowing when their next meal is coming along.

Bloodsucking and blood-drinking myth

The American mink does not “suck” the blood of its prey. This is a common misconception that has been applied to several mustelid species, none of which have the necessary jaw muscles to be physically capable of sucking blood. When it comes to mother’s milk “suckling” is a completely different reflex, and is something all mustelids stop doing once weaned. They also do not indulge in drinking blood.

Both of these myths are likely a construct of what some people heard or thought they saw, rather than what actually happened. Following an event of surplus killing, seeing uneaten animals with teeth marks left in their necks or skulls may have given rise to the myth that their blood was simply “sucked out” by the mink. Even if they could suck blood, this would serve the animal little dietary benefit since consuming meat is far more important.

Introduced range and fur farming

The American mink’s fur has been highly prized for use in clothing, with hunting giving way to fur-farming. Their treatment on fur farms has been a focus of animal rights and animal welfare activism.(14) Between the 1920s and 1950s, American mink were imported to Europe, the USSR and southern South America for fur-farming. Today in parts of Europe, released or escaped captive-bred American mink have been classified as an invasive species and linked to the decline of the European mink,(15)(16) as well as other small mammals and birds. It was both human vanity and a series of reckless releases that led to this ecological disruption, not the imported mink.

The American mink was also blamed for the decline of the Eurasian otter population in Great Britain. Further studies revealed that during the mid-20th century, many otters were dying from dieldrin poisoning; a organochlorine insecticide used by farmers.(17) Dieldrin was withdrawn from use in 1962 and eventually banned in 1989.(18)

Colour mutations

Due to selective breeding, farm-bred American mink can range in colour from beiges, greys, to a brown that is almost black.(19) You’ll often see them portrayed as pure white in visual media, but this colour too is only created through selective breeding. The American mink’s natural fur colour is brown.

SARS-CoV-2 outbreaks on mink farms

American mink are susceptible to SARS-CoV-2 infection, and there have been many outbreaks reported on fur farms across Europe. Several such outbreaks have occurred in the Netherlands, where more mink were dying than usual, with some showing symptoms of nasal discharge or difficulty breathing. Tens of thousands of captive-bred mink were gassed with carbon monoxide over fears of mink-to-human transmission. It is believed the virus may have spread amongst the mink via droplets, on feed or bedding, or in dust containing fecal matter.(20) The Dutch government had originally scheduled to ban mink farming in the country by 2024, but due to the mink’s susceptibility to covid-19, and possibility of mink-to-human transmission, this deadline was moved forward to March of 2021.(20)(21)

Other outbreaks on mink farms have occurred in the US states of Wisconsin and Utah, where thousands of mink died due to the virus itself, rather than from being culled.(22) It has been reported that the virus seems to burn itself out at every farm, once more than 90% of the mink have contracted the virus and developed antibodies.(20) It is important to emphasize that these outbreaks are “spill-overs” from the human pandemic, and that there’s no evidence the virus originated in American mink. Farmed mink likely contracted the virus from infected staff before spreading it amongst themselves.

Although little research has been conducted on the issue, it is unlikely that feral American mink will spread the virus in the wild. Unlike mink on fur farms which are kept in close quarters and can come into contact with infected mink or humans, both feral and wild mink are territorial and primarily solitary animals, and tend to only socialize when breeding. On the whole, we’re still in the early stages of understanding a complex virus. We should allow more evidence to surface before we, once again, misplace blame on the American mink. Although there is currently no evidence linking SARS-CoV-2 to an intermediate animal reservoir, keeping large groups of animals in industrial farming create perfect breeding grounds for viruses.(23)

Virus mutation

There have been reports that the SARS-CoV-2 virus, which humans transmitted to farmed mink, has mutated in these animals in Denmark. This mutation was able to be passed back to humans, and has been detected in a small number of the Danish population. While currently not found to be more severe than other strains of the virus, the Danish government believed this strain could be less sensitive to antibodies, and pose a risk that future vaccines won’t work if it’s allowed to spread within the human population. To lesson fears, the Danish government attempted to pass emergency legislation to cull all of the country’s 15-17 million farmed mink,(24) but nearly a week later this plan was supposedly dropped after receiving opposition from MPs over if the cull order was legal or properly scientifically base.(25) We say supposedly, because despite this political backlash the mass cull order commenced.(26)

It should be noted that some scientific experts find Denmark’s claim that the mutation could undermine vaccination efforts to be a bold statement. According to molecular epidemiologist Emma Hodcroft “It’s almost never the case that it’s such a simple story of one mutation and all your vaccines stop working.” Furthermore, Francois Balloux, the director of University College London’s Genetics Institute, stated that the virus is not likely to increase transmission, nor should it be more severe.(27)

Since the mink were burred in mass, shallow graves, built up gases from decomposition later caused their bodies to swell and be push out of the ground.(28) Social media went into a frenzy, with some news outlets using sensationalistic headlines such as “’Zombie’ Mink Rising”, when it’s nothing more than a case of poor burial planning.

Use in hunting (minkenry)

If properly trained, American mink make excellent hunting companions, as demonstrated by Joseph Carter “The Mink Man” on his YouTube channel.

Range map

Body length: 34–45 cm / 13–18 in (males), 31–37.5 cm / 12–15 in (females)
Tail length: 15.6–24.7 cm / 6–10 in (males), 14.8–21.5 cm / 6–8 in (females)
Weight: 500–1,580 g / 1–3 lb (males), 400–780 g / 1–2 lb (females)
Lifespan: Up to 10 years (wild), up to 11 years (captivity)
Range: North America, and introduced to parts of Eurasia and South America.
Conservation status: Least concern
Recognised subspecies(29)

  1. N. v. aestuarina — California lowland mink
  2. N. v. aniakensis
  3. N. v. energumenos — Western or Pacific mink
  4. N. v. evagor
  5. N. v. evergladensis — Everglades mink
  6. N. v. ingens — Alaskan mink
  7. N. v. lacustris — Hudson Bay mink
  8. N. v. letifera — Mississippi Valley mink
  9. N. v. lowii
  10. N. v. lutensis — Florida mink
  11. N. v. melampeplus — Kenai mink
  12. N. v. mink — Common mink
  13. N. v. nesolestes — Island mink
  14. N. v. vison — Eastern or little black mink
  15. N. v. vulgivaga — Southern mink

References

  1. Davidson, A., Griffith, H. I., Brookes, R. C., Maran, T., MacDonald, D. W., Sidorovich, V. E., Kitchener, A. C., Irizar, I., Villate, I., Gonzales-Esteban, J., Cena, A., Moya, I. and Palazon Minano, S. 2000. Mitochondrial DNA and paleontological evidence for the origin of endangered European mink, Mustela lutreolaArchived 12 May 2020 at the Wayback Machine. Animal Conservation 3: 345–357.
  2. Marmi, Josep, Juan Francisco López‐Giráldez, and Xavier Domingo‐Roura. “Phylogeny, evolutionary history and taxonomy of the Mustelidae based on sequences of the cytochrome b gene and a complex repetitive flanking region.” Zoologica Scripta 33.6 (2004): 481-499.
  3. Abramov, A. V. “A taxonomic review of the genus Mustela (Mammalia, Carnivora).” Zoosystematica rossica 8.2 (2000): 357.
  4. Harris, Stephen; Yalden, Derek (2008). Mammals of the British Isles (4th Revised ed.). Mammal Society.
  5. Seton, Ernest Thompson (1909). Life-histories of northern animals: an account of the mammals of Manitoba. New York: Scribner.
  6. Heptner, V. G.; Sludskii, A. A. (2002). Mammals of the Soviet Union. Vol. II, part 1b, Carnivores (Mustelidae and Procyonidae). Washington, D.C.: Smithsonian Institution Libraries and National Science Foundation.
  7. Kurta, A. 1995. “Mammals of the Great Lakes Region.” Ann Arbor, MI: The University of Michigan Press.
  8. Schlimme, K. 2003. “Neovison vison” (On-line), Animal Diversity Web. Accessed May 20, 2020.
  9. Feldhamer, George A., Bruce Carlyle Thompson, and Joseph A. Chapman. “Wild mammals of North America: biology, management, and conservation.” JHU Press, 2003.
  10. Harris, S., and D. W. Yalden. “Mammals of the British Isles, 4th edn (Southampton: Mammal Society).” (2008).
  11. Ibarra, José Tomás, et al. “Invasive American mink Mustela vison in wetlands of the Cape Horn Biosphere Reserve, southern Chile: what are they eating?.” Oryx 43.1 (2009): 87-90.
  12. Macdonald DW; Harrington LA, 2003. “The American mink: the triumph and tragedy of adaptation out of context. New Zealand Journal of Zoology, 30(4):421-441.
  13. Does surplus killing represent a waste of energy for foxes? Wildlife Online. Accessed 19 July 2020.
  14.  Dutch minister reverses battery and mink ban. 29 January 2009. Archived from the original on 09 May 2020.
  15. Clode, D. A. N. I. E. L. L. E., and DAVID W. Macdonald. “Invasive predators and the conservation of island birds: the case of American mink Mustela vison and terns Sterna spp. in the Western Isles, Scotland.” Bird Study 49.2 (2002): 118-123.
  16. Maran, T. and Henttonen, H. 1995. “Why is the European mink, Mustela lutreola disappearing? – A review of the process and hypotheses.” Annales Fennici Zoologici 32: 47–54.
  17. Jefferies, D. J., and H. M. Hanson. “The role of dieldrin in the decline of the otter (Lutra lutra) in Britain: the analytical data.” Journal of the International Otter Survival Fund 1 (2000): 95-143.
  18. BBC News. 11 June 2007. Otter numbers ‘continue to grow. Accessed 20 May 2020.
  19. Bachrach, Max (1953). “Fur: a practical treatise” (3rd ed.). New York: Prentice-Hall.
  20. Enserink, Martin. Coronavirus rips through Dutch mink farms, triggering culls. (2020): 1169-1169.
  21. FOUR PAWS Australia. 31 August 2020. “The Dutch government announced to shut down the mink farming industry in the country by March 2021“. Accessed 26 October 2020.
  22. Lewis, Sophie (2020) CBS NEWS. Thousands of mink dead from COVID-19 outbreaks in Utah and Wisconsin Accessed 12 October 2020.
  23. Greger, Michael. May 2009. Factory Farms: Recipe for Disaster“. Accessed 13 October 2020.
  24. Reuters. 04 November 2020. Denmark plans to cull its mink population after coronavirus mutation spreads to humans“. Accessed 06 November 2020.
  25. Kevany, Sophie and Carstensen, Tom. The Guardian. 09 November 2020. Denmark drops plans for mass mink cull after Covid mutation fears. Accessed 09 November 2020.
  26. Kevany, Sophie and Carstensen, Tom. The Guardian. 19 November 2020. Danish Covid mink variant ‘very likely extinct’, but controversial cull continues. Accessed 26 November 2020.
  27. BRANSWELL, H. STAT. 05 November 2020. Spread of mutated coronavirus in Danish mink ‘hits all the scary buttons,’ but fears may be overblown. Accessed 09 November 2020.
  28. Balk, Tim. New York Daily News. 25 November 2020. Dead mink, killed over COVID concerns, resurface in Denmark. Accessed 26 November 2020.
  29. Wilson, Don E. & Reeder, DeeAnn M. (Editors) 2005. Neovison vison in Mammal Species of the World. – A Taxonomic and Geographic Reference.

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