The Muroidea are a large superfamily of rodents, including mice, rats, voles, hamsters, lemmings, gerbils, and many other relatives. Although the Muroidea originated in Eurasia, they occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to difficulties in determining how the subfamilies are related to one another. Many of the families within the Muroidea superfamily have more variations between the families than between the different clades. A possible explanation for the variations in rodents is because of the location of these rodents; these changes could have been due to radiation or the overall environment they migrated to or originated in. The following taxonomy is based on recent well-supported molecular phylogenies.
The Arvicolinae are a subfamily of rodents that includes the voles, lemmings, and muskrats. They are most closely related to the other subfamilies in the Cricetidae. Some authorities place the subfamily Arvicolinae in the family Muridae along with all other members of the superfamily Muroidea. Some refer to the subfamily as the Microtinae or rank the taxon as a full family, the Arvicolidae.
The Ungava collared lemming or Labrador collared lemming is a small North American lemming.
The Richardson's collared lemming is a small North American lemming. At one time, they were considered to be a subspecies of the Arctic lemming, Dicrostonyx torquatus. Some sources believe they are a subspecies of the northern collared lemming, Dicrostonyx groenlandicus.
The northern collared lemming or Nearctic collared lemming, sometimes called the Peary Land collared lemming in Canada, is a small lemming found in Arctic North America and Wrangel Island. At one time, it was considered to be a subspecies of the Arctic lemming. Some sources believe several other species of collared lemmings found in North America are actually subspecies of D. groenlandicus.
The suborder Myomorpha contains 1,524 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings, and voles. They are grouped according to the structure of their jaws and molar teeth. They are characterized by their myomorphous zygomasseteric system, which means that both their medial and lateral masseter muscles are displaced forward, making them adept at gnawing. As in the hystricognathous rodents, the medial masseter muscle goes through the eye socket, a feature unique among mammals. Myomorphs are found worldwide in almost all land habitats. They are usually nocturnal seed-eaters.
The genus Lemmus contains several species of lemming sometimes referred to as the true lemmings. They are distributed throughout the Holarctic, particularly in the Palearctic.
The Canadian lemming or Nearctic brown lemming is a small North American lemming.
Nelson's collared lemming is a species of rodent in the family Cricetidae.
The Ogilvie Mountains collared lemming is a species of rodent in the family Cricetidae. It is found only in Yukon Territory, Canada. Its natural habitat is tundra.
The Arctic lemming is a species of rodent in the family Cricetidae.
The Unalaska collared lemming is a species of rodent in the family Cricetidae. This species is found on two islands, Umnak and Unalaska, in the Aleutian Archipelago of Alaska in the United States. Its natural habitat is tundra.
Eolagurus is a genus of rodent in the family Cricetidae. It contains the following species:
Although the bulk of its area is covered by ice caps inhospitable to most forms of life, Greenland's terrain and waters support a wide variety of plant and animal species. The northeastern part of the island is the world's largest national park. The flora and fauna of Greenland are strongly susceptible to changes associated with climate change.
A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings form the subfamily Arvicolinae together with voles and muskrats, which form part of the superfamily Muroidea, which also includes rats, mice, hamsters and gerbils. In popular culture, a longstanding myth holds that they exhibit herd mentality and jump off cliffs, committing mass suicide.
The Bruce effect, or pregnancy block, is the tendency for female rodents to terminate their pregnancies following exposure to the scent of an unfamiliar male. The effect was first noted in 1959 by Hilda M. Bruce, and has primarily been studied in laboratory mice. In mice, pregnancy can only be terminated prior to embryo implantation, but other species will interrupt even a late-term pregnancy.
