Synaptomys cooperisouthern bog lemming

Geographic Range

Southern bog lemmings are found in eastern North America, from southern Quebec and Manitoba in Canada to western Minnesota, to southwestern Kansas, and east to the Atlantic coast of the United States.


Southern bog lemmings occur in a wide variety of habitats. As their common name suggests, they are often found in sphagnum bogs and low moist places, but they are also found in grasslands, mixed deciduous/coniferous forests, spruce-fir forests, freshwater wetlands, marshes, and meadows. In Michigan, they can be found in clear cuts, old fields, or upland woods. They prefer areas with a thick mat of herbaceous and shrubby vegetation. Distribution of southern bog lemmings within their larger geographic range is patchy, which may in part be due to competition with meadow voles.

Southern bog lemmings use burrow systems 15 to 30 cm deep as well as surface runways, which are often located among roots of shrubs or beneath sphagnum moss. They also create round nests 15 to 30 cm in diameter that are made of dry leaves, grass, and some soft material like fur. Nests have 2 to 4 entrances. In the summer, nests are often placed on the ground amidst grassy vegetation or on top of sphagnum hummoks. In the winter, nests are commonly found 10 to 15 cm below the ground.

Physical Description

Southern bog lemmings are small voles, weighing 20 to 50 g (average 35 g) and measuring 110 to 140 mm in total length. Their dorsal pelage ranges in color from a chestnut to dark brown and has a grizzled appearance. The ventral side is silver-gray. Their incisors are broad and longitudinally grooved. The tail is short, barely longer than the hind foot. They have 4 toes and 1 small, nailed thumb on the forefeet and 5 toes on the hind feet. Females have 6 mammae, which differentiate this species from its closest relative, Synaptomys borealis, which have 8 mammae.

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    20 to 50 g
    0.70 to 1.76 oz
  • Range length
    110 to 140 mm
    4.33 to 5.51 in


Little is known about the mating systems of southern bog lemmings.

Southern bog lemmings breed year round, especially where food is not limited. Most young are born between April and September. Females are polyestrous--one captive individual bore 6 litters in 22 weeks. Females produce 2 or 3 litters per year in the wild. Gestation lasts from 23 to 26 days. Litter size averages 3 to 5 individuals, but can range from 1 to 8. Young weigh on average 3.7 g at birth and are born with no fur, blind, and with the ear pinnae folded over. Claws are also apparent at birth. By the end of their first week, young are well furred. Their eyes open at about 12 days of age. Females nurse their young for 3 weeks. Male southern bog lemmings reach sexual maturity in 5 weeks. Most individuals breed before they reach their maximum size.

  • Breeding interval
    Southern bog lemmings breed 2 or 3 times each year.
  • Breeding season
    Southern bog lemmings breed year round.
  • Range number of offspring
    1 to 8
  • Average number of offspring
  • Average number of offspring
  • Range gestation period
    23 to 26 days
  • Average weaning age
    3 weeks
  • Average age at sexual or reproductive maturity (male)
    5 weeks

Little is known about parental investment of southern bog lemmings. Females give birth in a nest or an underground burrow, and they nurse their young for 3 weeks.

  • Parental Investment
  • altricial
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female


Southern bog lemmings usually do not live for more than a year in the wild. In captivity, they may live up to 29 months.


Southern bog lemmings are active throughout the day and night, but are most active during the afternoon and night. They do not hibernate and are active throughout the year, but activity is limited below -7 ˚C. Southern bog lemmings can be colonial, living in groups of a few to several dozen individuals. They often live in the same area as other species of voles, white-footed mice, deer mice, shrews and moles. Southern bog lemmings generally dominate when they encounter other voles.

Southern bog lemmings may use runways and tunnels of other species, but they often create their own runways. Runways are 2.5 to 5 cm in diameter and are found in heavy vegetation. They trim new vegetation on their runways, which are usually littered with dead grass. Southern bog lemmings have distinctive runways, as piles of grass clippings approximately 8 cm in length are left nearby in addition to their droppings, which are light green in color. In wooded areas, they occasionally make runways by pushing up leaf mold.

Southern bog lemmings also use tunnels and burrows. Burrows are generally located at a depth of 15 to 30 cm beneath the ground. Side chambers are used for feeding, resting, storing food, or as a nest. During the summer, their nests may be placed on the ground amidst grassy vegetation or on top of sphagnum hummoks. Nests are round, 15 to 20 cm in diameter, and have 2 to 4 exits. They are generally composed of dry leaves, grass, and some soft material like fur, and are often concealed under stumps or mounds of sphagnum moss.

Home Range

The home range of southern bog lemmings varies from .25 to 1 acre.

Communication and Perception

Southern bog lemmings are thought to communicate intraspecifcally using scent marking from anal secretions. They also make squeaking vocalizations.

Food Habits

Southern bog lemmings mostly eat vegetation such as herbaceous plants, leaves, stems, seeds, particularly of bluegrass (Poa), white clover (Trifolium repens), and other grasses. They also eat sedges, mosses, fruits, fungi, bark, and roots. Bog lemmings snip stems near the ground to get access to the upper parts. Surrounding vegetation often prohibits the stems from falling, so additional snips must be made. Southern bog lemmings also eat some invertebrates such as slugs and snails, as well as adult and larval beetles. Their jaws are powerful and thought to be used extensively for gnawing. Captive individuals have been observed lapping water with their tongue. Because they consume so much green vegetation, their droppings are a characteristic uniform light green in color.

  • Animal Foods
  • insects
  • mollusks
  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • fruit
  • bryophytes
  • Other Foods
  • fungus


Southern bog lemmings have many predators, including owls, hawks, red foxes, gray foxes, domestic dogs, badgers, weasels, snakes, bobcats, and house cats.

Ecosystem Roles

Southern bog lemmings consume a variety of grasses and other vegetation and act as prey for a number of predators. They compete with other small rodents, particularly meadow voles. Meadow voles are superior competitors. Southern bog lemmings host external parasites such as mites, lice, and fleas. Their tunneling behavior also helps aerate the soil.

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known direct positive effects of southern bog lemmings on humans. Because they are important prey for many species and they aerate the soil, they help maintain a thriving ecosystem.

Economic Importance for Humans: Negative

In areas of high populations, increased tunneling activities of southern bog lemmings may be a nuisance in yards in wet areas. There are otherwise no known adverse effects of southern bog lemmings on humans.

Conservation Status

Because southern bog lemmings are widespread and they currently have no major threats, they are considered a species of least concern by the IUCN. Although populations are declining, the rate of decline is not considered fast enough to qualify for a more threatened category. Numbers are declining in part because of habitat destruction and overgrowth of bogs. Also, some human-driven habitat changes favor survival of Microtus, which tend to out-compete southern bog lemmings. These activities include deforestation, elimination of grasslands, and increased roadways. Two subspeices of southern bog lemmings are currently extinct: Kansas bog lemmings (Synaptomys cooperi paludis) and Nebraska bog lemmings (S. cooperi relictus).


Tanya Dewey (editor), University of Michigan-Ann Arbor, George Hammond (editor), Animal Diversity Web Staff, Gail McCormick (editor), Animal Diversity Web Staff.

Allison Poor (editor), University of Michigan-Ann Arbor.

Bridget Fahey (author), University of Michigan-Ann Arbor.



living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map


uses sound to communicate


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.

bilateral symmetry

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.


a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.


uses smells or other chemicals to communicate


active at dawn and dusk


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).


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


active during the night


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in


uses touch to communicate


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).


Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.


A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year


Nowak, R.M. Walker's Mammals of the World, 5th Edition. Johns Hopkins University Press.

Linzey, A. V. 1983. Syamptomys cooperi. Mammalian Species, no. 210: 1-5.

Kurta, A. 1995. Mammals of the Great Lakes Region. University of Michigan Press, Ann Arbor MI

"Animal Life Histories Database" (On-line).

Linzey, A., G. Hammerson. 2008. "Synaptomys cooperi" (On-line). IUCN Red List of Threatened Species Version 2010.4. Accessed March 30, 2011 at

Schwartz, C., E. Schwartz. 2001. The Wild Mammals of Missouri. Columbia, Missouri: University of Missouri Press.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington [D.C.]: Smithsonian Institution Press in association with the American Society of Mammalogists.