Lemming is the common name for various, small, furry rodents within the subfamily Arvicolinae (syn. Microtinae) of the Muridae family (sometimes Cricetidae), characterized by a small compact body with short legs and short tails. Arvicolinae, which sometimes is raised to family status as Arvicolidae, also includes rodents commonly known as voles and the muskrat. Lemmings have a widespread distribution across northern North America, Europe, and Asia and usually found in or near the Arctic, in tundra biomes.
The true lemmings comprise genus Lemmus, but among other genera including lemmings are Dicrostonyx (collared lemmings), Synaptomys (bog lemmings), and Myopus (M. schisticolor, wood lemming), all in tribe Lemmini, with the steppe lemmings of genera Lagurus and Eulagurus in tribe Microtini.
The renowned high reproductive rate of lemmings not only is tied to the success of the various species, but provides a larger function for their ecosystems. With populations reproducing very quickly, lemmings are an important food resource for predators in their area, including foxes, weasels, hawks, and owls.
Lemmings also are the subject of a myth that they follow one another in a migration that leads to their plunging off a cliff one after another in a mass suicide, a myth perpetuated in the 1956 Disney documentary White Wilderness using faked footage. However, as a result of their being associated with such behavior, they do serve as a frequently-used metaphor about people who go along unquestioningly with popular opinion, with potentially harmful consequences.
Lemmings, voles, and the muskrat (Ondatra zibethicus) comprise the subfamily Avicolinae of the family Muridae of the order Rodentia. Muridae is a huge family that has over 1,300 species, while about 143 species are placed in the 26 genera of the subfamily Arvicolinae, the third largest subfamily of Muridae (Jordan 2004). Arvicolinae is also known by its junior synonym (Microtinae). The Muridae family, however, has long been undergoing considerable revision. Arvicolinae sometimes is raised to the level of family as Arvicolidae, and for some time the voles and lemmings were placed in the Cricetidae family with the closely related hamsters (Jordan 2004).
Both voles and lemmings tend to be small (typically less than 100 grams or 3.5 ounces), stocky animals with short legs and tails and compact bodies. The muskrat by far the largest member of the subfamily, weighing as much as 1820 grams (4 pounds) (Jordan 2004).
The lemmings generally are seen as being in the tribe Lemmini, with the four genera of Lemmus, Dicrostonyx, Synaptomys, and Myopus. However, the term lemming is a common name, not a taxonomic designation, and some members in tribe Microtini also are known as lemmings, notably members of the genera Lagurus and Eulagurus, whose members are known as steppe lemmings.
In general, lemmings are similar to the voles but tend to have, in most species, more thickset, robust bodies and shorter tails (Jordan 2004). Lemmings weigh from 30 to 112 grams (1.1 to 4.0 ounces) and are about 7 to 15 centimeters (2.8 to 5.9 inches) long. They generally have long, soft fur, and very short tails. Member of the genus Lemmus, the true lemmings, have a fur that is highly patterned with gray, white, brown, and buff colors. Members of the genus Dicrostomyx, the collared lemmings, tend to be pure white in winter and develop in winter an enlarged third and fourth claw on the forefeet, a feature unique among rodents (Jordan 2004).
Lemmings exhibit both diurnal and nocturnal active, often active both night and day. Lemmings do not hibernate through the harsh northern winter. They remain active, finding food by burrowing through the snow and utilizing grasses clipped and stored in advance. They are solitary animals by nature, meeting only to mate and then going their separate ways.
Lemmings are herbivorous, feeding mostly on leaves and shoots, grasses, and sedges in particular, but also on roots and bulbs. Like other rodents, their incisors grow continuously, allowing them to exist on much tougher forage than would otherwise be possible.
Like all rodents, lemmings have a high reproductive rate and can breed rapidly when food is plentiful. The behavior of lemmings is much the same as that of many other rodents that have periodic population booms and then disperse in all directions, seeking the food and shelter that their natural habitat cannot provide. Young are born blind and naked, but develop rapidly and wean as quickly as two weeks after birth, and the young may themselves reproduce before they are one month of age (Jordan 2004).
In the wood lemming (Myopus schisticolor), three different genotypes of females are born, with each genotype producing different sex ratios of offspring. Some produce at the normal ratio of one male to one female, while the others produce either at a one male to three female ratio or all female litters (Jordan 2004).
Lemmings of northern Norway are one of the few vertebrates who reproduce so quickly that their population fluctuations are chaotic (Turchin and Ellner 2000; Turchin and Hanski 1997), rather than following linear growth to a carrying capacity or regular oscillations. It is unknown why lemming populations fluctuate with such variance roughly every four years, before plummeting to near extinction (Fuller 1994).
While for many years it was believed that the population of lemming predators changed with the population cycle, there is now some evidence to suggest that the predator's population may be more closely involved in changing the lemming population (IR 2003).
Misconceptions about lemmings go back many centuries. In the 1530s, the geographer Zeigler of Strasbourg proposed the theory that the creatures fell out of the sky during stormy weather (also featured in the folklore of the Inupiat/Yupik at Norton Sound), and then died suddenly when the grass grew in spring (Kruszelnick 2004).
While many people believe that lemmings commit mass suicide when they migrate, this is not the case. Driven by strong biological urges, they will migrate in large groups when population density becomes too great. Lemmings can and do swim and may choose to cross a body of water in search of a new habitat (Woodford). On occasion, and particularly in the case of the Norway lemmings in Scandinavia, large migrating groups will reach a cliff overlooking the ocean. They will stop until the urge to press on causes them to jump off the cliff and start swimming, sometimes to exhaustion and death. Lemmings are also often pushed into the sea as more and more lemmings arrive at the shore.
The myth of lemming mass suicide is long-standing and has been popularized by a number of factors. In 1955, Carl Barks drew an Uncle Scrooge adventure comic with the title "The Lemming with the Locket." This comic, which was inspired by a 1954 National Geographic article, showed massive numbers of lemmings jumping over Norwegian cliffs (Blum 1996). Even more influential was the 1958 Disney film White Wilderness in which footage was shown that seems to show the mass suicide of lemmings (Kruszelnicki 2004; Woodward). The film won an Academy Award for Documentary Feature. However, it is now known that the footage was staged, using editing, tight camera angles, and an illusion of a migration and suicide of lemmings going into a sea. First of all, the lemmings used for White Wilderness were flown from Hudson's Bay to Calgary, Alberta, Canada, a landlocked area. Secondly, the lemming migration involved lemmings running on a turntable covered with snow. Then they were herded over the cliff or launched (Woodward; Blum 1996; Kruszelnicki 2004).
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