Northern bog lemmings (Synaptomys borealis) occur across North America from Labrador to southern Alaska. They are uncommon in northwestern and eastern Canada. There is an isolated population south of the St. Lawrence River in the Northern Appalachian Mountains (Banfield, 1974).

Their geographic range is thought to be explained by their high affinity for boreal habitats, these boreal forests have been retreating northward along with S. borealis.

The first fossil record of Synaptomys was found in the Wisconsin Glacial age deposits in the Great Basin, where they are no longer found. Evidence suggests that a glacial meltwater stream provided a local environment which was more mesic and supported a restricted population of lemmings in this canyon-bottom region (Mead et al, 1992).

Biogeographic Regions: nearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Labrador west to central Alaska, south to Washington, Montana, southeastern Manitoba and northern New England (see Clough and Albright 1987 for recent records from Baxter State Park, Maine, and from Mt. Moosilauke, Grafton County, New Hampshire). Distribution is apparently spotty even in the center of range in central Canada.

Tail: 20-27mm

Hing foot: 18-21mm (Banfield, 1974)

Synaptomys borealis is a microtine rodent. They have a stocky build, with short legs and a tail which is slightly longer than their hind foot (Wilson et al, 1999). Their ears are relatively small and their nose is blunt. The pelage is coarse and appears ruffled, the colour varies from grayish brown to chestnut brown on their dorsal side and pale gray ventrally (Banfield, 1974). The bicoloured tail is brown above and white below (Wilson et al, 1999).

Synaptomys borealis can be identified by several cranial features. They have a short rostrum, projections on the upper incisors, and mandibular incisors which are thin and pointed. They can be differentiated from their closest relative, Synaptomys cooperi, (southern bog lemmings) by the absence of closed triangles on their mandibular molars and a palate which extends in a sharply pointed, backward projecting spine (Banfield, 1974).

Flank glands of adult males are often clearly marked by a patch of white hair (Banfield, 1974). Females possess eight teats of which two are pectoral pairs and two are inguinal pairs. Synaptomys cooperi has six mammae (Banfield, 1974).

Northern bog lemmings do not have any significant sexual dimorphism.

Range mass: 27 to 35 g.

Range length: 122 to 144 mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike

Length: 14 cm

Weight: 34 grams

• Terrestrial

Synaptomys borealis primarily live in burrows among sedges and grasses (Wilson et al, 1999). They can be found where moisture levels are high and growth of sedges and grasses are sufficient to provide cover as well as act as their food supply (Wilson et al, 1999). During the snow free months this species is active both above and below ground, though most activity at this time occurs below ground to avoid predation by the high diversity of mammalian and avian predators (Wilson et al, 1999). During the winter months this risk of predation is lowered and most activity occurs above ground. Lemmings construct globular nests composed of mosses, grasses, and sedges at ground level just beneath the snow in the winter months and build their nests underground in the summer months (Banfield, 1974). They remain active year-round.

Foraging activities are largely confined to runway systems where vegetation is harvested and either consumed or removed to underground nests via escavated burrow systems (Wilson et al, 1999).

Synaptomys borealis primarily frequent sphagnum-Labrador tea-black bogs but they are also found to live among deep, moist spruce woods, wet, subalpine meadows, and alpine tundra (Mead et al, 1992).

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: tundra ; savanna or grassland ; mountains

Wetlands: bog

Comments: Sphagnum bogs, wet meadows, moist mixed and coniferous forests; alpine sedge meadows, krummholz spruce-fir forest with dense herbaceous and mossy understory, mossy streamsides (Clough and Albright 1987). Occupies burrow systems up to 1 foot deep and surface runways. Young are born in nests that may be underground or on the surface in concealing vegetation.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Northern bog lemmings primarily feed on sedges and grasses. They actively clip sedges, grasses, and leafy plants to line the above ground runways between burrow entrances (Wilson et al, 1999). Runways without clippings indicate an abandoned burrow system (Banfield, 1974).

Comments: Feeds on grasses, sedges, and other herbaceous vegetation.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Hundreds of known locations.

10,000 to >1,000,000 individuals

Maintains a home range of probably less than 1 acre. Population densities may range up to 3 dozen per acre. Very sociable; may be found in small colonies.

Comments: Active day/night throughout the year.

The breeding season for S. borealis extends from May to late August. Their litter sizes ranges from two to eight, with an average size of four to five young per litter (Wilson et al, 1999). Female S. borealis are capable of breeding one day after giving birth and are thus capable of having two or three litters per breeding season (Wilson et al, 1999). This indicates the potential for rapid population growth under ideal environmental conditions, though they tend to be uncommon throughout their range.

Breeds May-August. Gestation lasts probably 3 weeks. Litter size is 2-8 (average 4). Several litters per year. At least some breed during the summer of their birth.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Widespread distribution extending from Alaska to Labrador and south to portions of the northern U.S., but populations are localized; population sizes are not known for any location, although nowhere does this mammal appear to be common.

Other Considerations: Note that pitfall or Museum Special snap traps appear to be approximatley 10 times as effective for sampling than Sherman traps and that mortality is >50% with Sherman traps supplied with bedding and food (Reichel and Beckstrom 1993, 1994).

Global Short Term Trend: Unknown

Comments: Unknown.

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Management Requirements: Based on an evaluation of the limited available information, Reichel made the following management recommendations, intended specifically for Montana but perhaps generally applicable to other areas as well: maintain a 100-m buffer for management activities around riparian areas/corridors where sphagnum mats occur; minimize domestic livestock grazing in drainages with sphagnum mats present (range conditions in these riparian areas should be maintained in good to excellent categories; if current range condition is fair to poor, stocking rates should be reduced to a point where rapid recovery occurs); avoid human activities that alter streamflow in drainages with spagnum mats present.

Management Research Needs: More information is needed on responses of populations to various land management procedures.

Biological Research Needs: Little is known of the ecology of the species. Essentially all publications deal only with distribution or taxonomy. Much additional information is needed on population parameters, movements, and habitat requirements.

Global Protection: Few to very many (1 to >40) occurrences appropriately protected and managed

Comments: In Montana 2 sites are in Glacier National Park and 1 in a USFS Special Botanical Area. In Washington 3 sites are USFS Wilderness Areas.

Needs: Unknown

None known.

Positive effects are unknown, though it is likely that the presence of Northern bog lemmings contributes to a healthy ecological community.

Comments: Included in the genus Mictomys by some paleontologists (e.g., Koenigswald and Martin 1984), but most authors have treated Mictomys as a subgenus of Synaptomys (Hall 1981; Jones et al. 1986, 1992; Musser and Carleton, in Wilson and Reeder 1993, 2005).