- Scientific name: Synaptomys cooperi
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Special Concern (MA Endangered Species Act)
Description
A southern bog lemming
The southern bog lemming is a small, chunky rodent with small eyes and ears that are nearly concealed in the long, loose, shaggy fur. The skull is broad, and the short rostrum (snout) gives this species an abrupt profile. This species is distinguishable by the combination of its short tail (only slightly longer than its hind foot) and grooved upper incisors. Females have six mammae.
The sexes are colored alike, with no apparent seasonal variation. The adult pelage (fur) is brown to chestnut above, with a grizzled appearance. The sides and underparts are silvery, with no sharp line of demarcation on the sides. The tail is indistinctly bicolored, brownish above and whitish below. The feet are brownish black. Old males may have white hairs growing from the center of the hip glands. Immatures are darker and duller than adults. A single annual molt occurs from spring to autumn.
The sexes are equal in size. Measurements range from 11.5–13.5 cm (4.5-5.3 in) in total length, the tail 1.8–2.4 cm (0.7-0.9 in). Weights vary from 20-40 g (0.7-1.4 oz).
The southern bog lemming resembles the eastern meadow vole (Microtus pennsylvanicus) but doesn’t get as large, has a much shorter tail, and broader upper incisors with a distinct groove running down the middle of the front face of each tooth. Both species are grassland animals, but the southern bog lemming is more adaptable and is found in many situations which the meadow vole usually avoids. The southern bog lemming occurs in what is essentially sub-marginal meadow vole habitat. The larger, more aggressive meadow vole will appropriate the best of the moist, lush meadow areas or grassy bogs for its own use wherever possible, forcing the bog lemming into diverse types of habitats, which appear to have little in common: dry upland fields, sedge-lined forested stream banks, and wet sphagnum bogs.
The only other species with which a southern bog lemming might be confused is the woodland vole (Microtus pinetorum); also known as the pine vole. Woodland voles are russet or auburn, not dull grey brown, with sleek, short, mole-like pelage and ungrooved upper incisors. Like the bog lemming, the woodland vole inhabits diverse habitats. It is found in deciduous forests, grasslands, meadows, and orchards. The woodland vole also occurs in marshes and swamps but favors well-drained uplands.
The northern bog lemming (Synaptomys borealis) has never occurred in Massachusetts, at least in modern times. It is very rare in the northeastern U.S. and found in only a few isolated locations. The southernmost record is from Fabians at the foot of Mt. Washington, New Hampshire, and its range extends northward from there into northern Labrador and west to Alaska.
Life cycle and behavior
Southern bog lemming phenology wheel
The southern bog lemming is active year-round as well as active both day and night. This species is a quiet, unobtrusive little field vole that generally travels slowly. If frightened, it can move fast and can swim well. It occurs in scattered colonies often of a very temporary nature and is sometimes found with red-backed voles, meadow voles, moles, shrews, white-footed mice and deer mice. Evidence of these colonies are well stacked piles of grass cuttings, each an inch or so in length, circular patches of grass several feet in diameter, yellowed and dry, where the stems have been nibbled out from beneath, and small bright green oval scats (droppings). This green excrement is a unique characteristic of a bog lemming; other voles tend to void darker feces.
Bog lemmings create a complex system of short, crisscrossed tunnels or burrows with side chambers which are used for feeding, resting, storing food. These tunnels measure about 2–5 cm (1–2 in) in width and are 15–30 cm (6–12 in) below the surface. They are well-defined and maintained and may contain little piles of cut grass stems and bright green scat. They are built in sphagnum and deep leaf mold by the cutting and trimming activities of foraging individuals using specially adapted molar teeth. These teeth never form closed roots and continue to grow out of the gums as fast as the vole wears them down.
Breeding occurs from early spring to late autumn, and the gestation period is 21 to 23 days. The globular nest is usually an enlarged section of the burrow, lined with dried leaves of grasses and sedges and sometimes with bits of fur and feathers. Its exterior diameter is 15–20 cm (6–8 in) with the interior diameter 5–8 cm (2–3 in). It may have 2 to 4 entrances. In winter, the nest may be found 10–15 cm (4–6 in) underground; in summer, it is often concealed in tussocks of grass or amid other surface cover. Several litters are produced annually which may contain from 1 to 8 young, but 2 to 5 is usual. Newborns are blind, naked, and helpless at birth and weigh an average of 4 g (0.14 oz). Growth is rapid, and hair is evident when young are about 6 days old. Their eyes open when they reach 10 to 12 days of age, and weaning is completed by the end of their third week of life. The life expectancy of a southern bog lemming is 1 to 1 1.5 years.
The diet of the southern bog lemming consists of succulent stems, leaves, and seeds of grasses and sedges—namely poverty grass, timothy, and blue grass. In addition, ferns, mosses, liverworts, fungi, ground pine, bark, and insects are occasionally consumed. The bog lemming has many predators including foxes, skunks, weasels, house cats, and raccoons. Several species of owls, hawks, and snakes also take a toll on this species. Fleas, ticks, lice, and mites infest the southern bog lemming externally, and it harbors internal parasites such as tapeworms, flukes, and roundworms.
Population status
Historically, the southern bog lemming has been extremely rare in Massachusetts. Records show that prior to 1978, six individual sightings or “populations” were documented from five different locations (Belchertown, Dunstable, Lunenburg, Plymouth, and Wareham). Historical records (pre-1970) are known from Bolton, Greenfield, Lunenburg, Plymouth, Wareham, Wayland, and more recent records from Belchertown, New Salem, and Ware. In total, the southern bog lemming has been documented in 9 of the 351 municipalities in 6 of the 14 counties, but no records have been documented since 1994. The southern bog lemming is currently listed as a species of special concern in the state of Massachusetts.
Distribution and abundance
The southern bog lemming occurs from Quebec, west to southeastern Manitoba, south to southwestern Kansas, east through northern Arkansas, Kentucky, and central Tennessee south to western North Carolina and Virginia and western Maryland to the Atlantic coastal plain of Maryland, Delaware, and New Jersey, and northward through New England to Cape Breton Island.
Habitat
The southern bog lemming occurs from Quebec, west to southeastern Manitoba, south to southwestern Kansas, east through northern Arkansas, Kentucky, and central Tennessee south to western North Carolina and Virginia and western Maryland to the Atlantic coastal plain of Maryland, Delaware, and New Jersey, and northward through New England to Cape Breton Island.
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
The greatest threat to the southern bog lemming is destruction of habitat.
Conservation
Protection of woodland vernal pools with understory, sedge meadows, and wooded wetland type habitats need to be maintained. Populations of the southern bog lemming are believed to be small and isolated, and if lost, may not become easily re-established.
References
Doutt, J.K., C.A. Heppenstall, and J.E. Guilday. 1977. Mammals of Pennsylvania. 4th ed. Harrisburg, Pennsylvania: Pennsylvania Game Commission.
Godin, A.J. 1977. Wild Mammals of New England. Baltimore, Maryland: Johns Hopkins Press.
Hazard, E.B. 1982. The Mammals of Minnesota. Minneapolis: University of Minnesota Press.
Linzey, A.V. 1983. Synaptomys cooperi Baird, 1858. Mammalian Species 210: 1–5.
Merritt, J.F. 1987. Guide to the Mammals of Pennsylvania. Pittsburgh, Pennsylvania: University of Pittsburg Press.
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| Date published: | April 22, 2025 |
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