populates the taiga (Niethammer, 1990). It also occupies areas of the coniferous forest zone from Norway to eastern Siberia, as well as areas of northern Mongolia (Nowak 1999). It is especially abundant in many areas of central Sweden (Fredga et. al., 1998), Finland (Eskelinen, 1997) and Russia (Amori, 2001).
lives in the moss layer on the floor of wet nordic coniferous woodlands (Niethammer, 1990). It may sometimes also be found living under the roots of trees and beneath fallen tree trunks (Nowak, 1999). In general, it is restricted to the forests (Fredga et. al., 1998).
The Wood lemming is ash-gray with a cinnamon-colored saddle. Due to its similarity in molar pattern to the Norway lemming, systematists have often assigned the Wood lemmings to the genus Lemmus. However, the Wood lemming has distinctively less hair on the soles of its feet and a wide thumb claw that distinguishes it from the Norway lemming (Niethammer, 1990).
Wood lemmings have a soft pelage, dense and slaty black above with a definite reddish brown area on the contour of the back extending from the shoulders to within 15mm of the base of the tail (Nowak, 1999). The rest of the coat is slightly paler on the ventral surface. The peculiar metallic luster on the upper parts is produced by silvery tips on the shorter hairs, with an indistinct showing of black guard hairs. The tail is heavily furred. The palms are naked. The hind feet are densely haired behind the pads but are naked in front of the pads, like the palms of the forefeet (Nowak, 1999). There is no substantial difference in the coloration of the sexes, nor is there much seasonal variation in color. The winter coat is slightly longer than the summer pelage (Nowak, 1999).
Wood lemmings are stout rodents with small ears that project little beyond the fur but which are well developed, rounded and well haired. Valves in the ears regulate the size of the ear openings (Nowak, 1999). The thumb of the hand is small but bears a large, flattened nail with parallel sides and a notch at the end. In this respect Wood lemmings somewhat resemble Lemmus, but are smaller (Nowak, 1999).
High population densities may occur (Niethammer, 1990), and locally limited migrations are known as well (Eskelinen, 1997).
Male home ranges are consistently larger than female. On average, males move distances 4-12 times further than females (Andreassen et. al., 1991).
gnaw tunnels in moss cushions, feeding mainly on these mosses (Niethammer, 1990). In autumn, they collect and store many moss piles in the spruce forests they occupy in various parts of Finland. They hide their stores under stones, tree trunks and other areas where it is sheltered from the rain. Sometimes stores are kept in open places, such as under growing trees, but this is rare. The areas where they collected mosses are clearly distinguishable from feeding areas. In feeding areas only the tips of the mosses were taken, while in collecting patches the mosses were taken whole. The stores are generally eaten during that following winter. Stores are thought to be especially important during the early winter; 50% of them are consumed completely (Sulkava et. al., 1996).
Wood lemmings have a high metabolic rate, typical of rodents living in high latitudes (Saarela et. al., 1993).
Foods eaten include: mosses, rushes, grasses, sedges (Niethammer, 1990). Specifically, stems of red wortleberry, and the bark of juniper (Nowak, 1999).
Wood lemmings have numerous predators including owls and buzzards (Niethammer, 1990).
Myopus is likely to be seen only in years when its populations become unusually large (Nowak, 1999). Because it is dependent on a relatively narrow set of ecological conditions that are easily disrupted by human activities, it is designated on the "red list" as Lower Risk - near threatened by the IUCN (Nowak, 1999).
Much of the studies done on Wood lemmings have focused on their sex chromosomes. Sex determination in the Siberian Wood lemming has shown there exists an female-biased sex ratio among the lemmings. This sex-bias is the result of a high concentration of the X-chromosome. The X-chromosome in this case induces, in excess, the development of XY females (Gileva et. al., 1991). Their populations have only 20% males, both in captivity and in the wild. Some females have one X-chromosome and one Y-chromosome in each of their body cells, like males of other species. To further this sex bias among Wood lemmings, the XY females develop egg cells with XX-chromosomes in their ovaries. The X-chromosome of the females also differs from the X-chromosome found in the males; there is a female-determining and a male-determining X-chromosome. Possibly this is the means by which the Wood lemming increases its birth rate. Because one male can mate with several females the propagation of these animals may be most successfully accomplished by increasing the number of females in the population (Niethammer, 1990).
Jessica Ollendorff (author), University of Michigan-Ann Arbor, Ondrej Podlaha (editor), University of Michigan-Ann Arbor.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
uses smells or other chemicals to communicate
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
an animal that mainly eats leaves.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
An animal that eats mainly plants or parts of plants.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
places a food item in a special place to be eaten later. Also called "hoarding"
uses touch to communicate
Coniferous or boreal forest, located in a band across northern North America, Europe, and Asia. This terrestrial biome also occurs at high elevations. Long, cold winters and short, wet summers. Few species of trees are present; these are primarily conifers that grow in dense stands with little undergrowth. Some deciduous trees also may be present.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
Amori, G., "UNEP-WCMC Database - Animals" (On-line). Accessed November 17, 2001 at http://www.unep-wcmc.org/index.html?http://valhalla.unep-wcmc.org/isdb/Taxonomy/tax-common-result.cfm?Common=43799~main.
Andreassen, H P., , Bondrup, Nielsen S.. 1991. Home range size and activity of the wood lemming *Myopyus schisticolor*. Holarctic Ecology, 14 (2): 138-141.
Eskelinen, O., 1997. On the population fluctuations and structure of the wood lemming *Myopus schisticolor*. Zeitschrift Fuer Saeugetierkunde, 62 (5): 293-302.
Fredga, Karl, , Fedorov, Vadim. Nov., 1998. The wood lemming (*Myopus schisticolor*) in Sweden 1998. Fauna Och Flora (Stockholm), 93 (3): 113-117.
Gileva, E.A., , Fedorov, V.B.. 1991. Sex ratio XY females and absence of inbreeding in a population of the wood lemming *Myopus schisticolor* Lilljeborg 1844. Heredity, 66 (3): 351-356.
Niethammer, Jochen, 1990. Burrowing Rodents. Pp. 233, 234, 260, 261 in Parker, Sybil P., ed. Grzimek's Encyclopedia of Mammals. McGraw-Hill Publishing Co..
Nowak, Ronald M., 1999. Walker's Mammals of the World. Baltimore and London: The Johns Hopkins University Press.
Saarela, Seppo, , Hissa, R.. 1993. Metabolism, thermogenesis and daily rhythm of body temperature in the wood lemming, *Myopus schisticolor*. Journal of Comaparative Physiology - B, Biochemical, Systemic, & Environmental Physiology., 163 (7): 546-555.
Sulkava, Seppo, , Sulkava, Pertti, Kaikusalo, Asko. 1996 (1997). Selection and consumption of mosses in the food stores of the wood lemming. *Myopus schisticolor* Lillj., in Finland. Aquilo Ser Zoologica, 29 (0): 25-32.