A weasel weighs less than one-fiftieth of a human, so how did it come to dominate the Water Margin?

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Starting in the 16th century AD, French, British, Dutch and Russian colonists on the North American continent began the fur trade with Eurasia. In 1803, the U.S. government purchased the vast Louisiana territory from the French, then carried out the famous Lewis and Clark Expedition, exploring the enormous western frontier and joining North America's "Great Western Development" club. By the mid-19th century, before the "California Gold Rush" had even begun, this "fur trade boom" had already entered its peak period.

Late 19th century, a fur trader in Alberta, Canada. Image: C.W. Mathers and Ernest Brown / Library and Archives Canada

Behind the boom, the fur-bearing animals that sustained the fur trade sharply declined in number. The first to suffer was the American beaver, and another main target of fur hunters was the animal we're discussing today, the American mink (Neovison vison). To this day,the American minkis stillone of the world's most important and most common fur-bearing animals。

A white chin "stolen" from sneaking food

Calling the American mink the American weasel is not entirely wrong. The genus Martes (martens) and the genus Mustela (weasels) are both members of the subfamily Mustelinae within the family Mustelidae, while Mustelidae also contains other groups such as the subfamily Lutrinae (otters) and the subfamily Melinae (badgers). The Chinese characters "diao" (marten) and "you" (weasel) do not correspond exactly to these two genera in the use of Chinese species names; for example, the common pet ferret (the domestic ferret, M. putorius furo) and its wild ancestor the European polecat (M. putorius) both belong to the genus Mustela. Generally speaking, though, in our mindsweasels are small and slenderwith athin tailthat hasa tuft of fur。

at the tip. The stoat (M. erminea) of the genus Mustela fits people's usual impression. Image: Manfred Danegger / photoshot.com

Although its name is "marten," the American mink is actuallymore closely related to the various weaselsin evolutionary terms. Taxonomically, the genus Neovison was not separated from the genus Mustela until 1997. In appearance, the American mink looks more like a marten: it islargerthan the little cuties of the genus Mustela, and considerably stockier too. An adult male weighs 0.9-1.6 kg and has a body length of about 60 cm, while a female weighs 0.7-1.1 kg and is 50 cm long, and like martens it also hasa fluffy, thick tail。

The American mink is sturdier, and has a big furry tail. Image: Igor Shpilenok / naturepl.com

As the name suggests, the American minkloves water, and its slender, streamlined body is well suited for burrowing and swimming. There is also a "traitor" in the genus Mustela, the European mink, whose appearance is very similar to the American mink and which has also adapted to a semi-aquatic environment, but is smaller in size. The American minkis dark brown all over, with only its chin being white, while the European mink often has a white upper lip, allowing a rough distinction.

American mink: "The white chin is natural, not from sneaking food and forgetting to wipe my mouth, thanks." Image: Igor Shpilenok / naturepl.com

The European mink forgot to wipe its whole mouth (just kidding!). Image: Stefan Meyers / ardea.com

The American mink's winter fur is longer and denser than the European mink's, soft and tight, and in summer it molts into short, sparse summer fur. Its oilyguard hairsand the fineunderfurbeneath them canrepel water. Because of its larger size and good quality, this cold-proof, waterproof "mink coat" naturally brought the American mink the mortal danger of the fur trade. And the largersea mink(N. macrodon), also of the genus Neovison, which once lived mainly along the Atlantic coast of the northeastern United States, had by the late 19th century alreadygone extinct because of hunting for the fur trade。

The American mink's waterproof mink coat. Image: George Sanker / NPL

Chemical weapons ahead, back off quickly!

The typical habitat of the American mink is the "water margin": it prefers rocky riverbanks or lake shores with dense vegetation, and also likes marshes and wetlands. The American mink is strongly territorial; both females and males have their own territories, and same-sex territories hardly overlap, but opposite-sex territories overlap in distribution, making it easy to flirt with each other. The two large anal glands at the rear can producesecretions with a memorable odor, which can be used both to mark territory and, when threatened, sprayed out to deter enemies, though unlike a skunk it cannot aim.

Vegetated banks are a favored habitat of the American mink. Image: Leonard Rue Enterprise / Animals Animals

As long as it can live by the water, the American mink is not very picky about housing conditions; burrows in riverbanks, hollow tree stumps and the like are all good choices. Theburrowthat the American mink digs itself with its claws is 90 cm deep and can be more than 3 m long, winding about with several exits, and the innermost bedroom is lined with dry grass and leaves. They also make use of other animals' dwellings, such as burrows abandoned by badgers, muskrats and skunks.

Inside rotted wood seems not bad either. Image: Erwin & Peggy Bauer / Animals Animals

The little overlord of the weasel family, afraid of nothing!

Although it is a relative of weasels and looks like a marten, when walking on land the American mink resembles otters somewhat, bounding forward in a "rocking" motion; once in the water it is also "like an otter in water," and as long as the temperature is not too low, it canswim in the water for several hours, and diving to catch fish is no problem either. The American mink, like its relatives in the genus Mustela, is aterrible killer, taking fish, frogs, shrimp and crabs, small mammals and waterfowl alike; its menu could be said to span sea, land and air, adapting to local conditions. Not only that, when facing predators larger than itself, the American mink dares to fight back head-on, with a powerful presence.

Catching fish, easy as pie. Image: Brian Bevan / ardea.com

Amphibians, no problem. Image: Gordon & Cathy Illg / Animals Animals

In its native North America, the mink'sfood is mainly fish. But relying on the weasel family's signature "leap onto the back and bite the neck," it is not rare for the American mink to kill gulls and cormorants, and small waterbirds of the rail family are even more routine fare. Among mammals, rodents and hares are also common prey of the American mink. From an evolutionary perspective,the weasel family's killer nature is related to their body size: a slender, slim body is very suitable for burrowing to prey on various burrowing prey, but at the same time it has a larger relative surface area than the rounder ones, causing heat to be lost faster. To maintain an energy balance, it has no choice but to eat more.

A big bird (a northern gannet subadult)? Not afraid at all. Image: John W Anderson / via GBNNSS

Can farming solve the problem?

The American mink's ⟧71⟧invasion ⟧72⟧of Eurasia ⟧73⟧is "thanks" toInvasionWant"Thanks" tohumans' obsession with fur. The American mink, clad in thick winter fur, does not hibernate in winter, making it very suitable to be hunted as a fur-bearing animal. In the late 19th century, due to growing demand for mink fur, people began farming American mink. By around 1965, there were more than 7,200 mink farms across the United States. As late as 1998, nearly 3 million mink pelts were still produced each year. Naturally agile, they often staged escapes from farms.

An American mink staging a "farm escape" drama. Image: Paul Hobson / naturepl.com

The escape of farmed minkseems inspiring, but in factis a potential threat to wild populations. Farmed mink are generally larger than wild individuals, and driven by territoriality they may well reduce the number of wild mink through competition for resources. Hybridization between farmed individuals and wild mink will also mix the former's genetic information into wild populations. Because farmed strains lack genetic diversity and face no appropriate selection pressure, this"genetic pollution" may cause wild populations to "degenerate", becoming less adaptable to the environment and threatening the population's stable existence.

In the early 20th century, the American mink was introduced to Europe and South America for farming, and due to farm escapes and the "rescue" efforts of some animal protectionists, it likewise invaded the wild environment. In the Eurasian "territory," the American mink's ecological niche was originally occupied by the Eurasian otter; the two have very similar diets, and after invading, the American mink turned more to land prey to avoid resource competition. Today, theAmerican mink, spread across the northern part of Eurasia, poses a certain threat to local birds and small mammals。

An American mink caught in a trap. Image: Andrew Harrington / naturepl.com

Thus it is:

Reaching the nine heavens to snatch birds, showing a killer's true colors, deadly as a weasel

Diving the five oceans to catch fish, with an otter's flair, looking like a marten

This is the 250th article of the 4th year of the Species Calendar, from Species Calendar author @Lu Ping.

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