Synaptomys borealis
northern bog lemming

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). (Banfield, 1974; Mead, Bell, and Murray, 1992)

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). (Banfield, 1974; Mead, Bell, and Murray, 1992; Wilson and Ruff, 1999)

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. (Banfield, 1974; Wilson and Ruff, 1999)

S. borealis repeatedly leave fresh droppings along their runways, creating a scent 'signpost' which identifies it as an active runway (Wilson et al, 1999). They often share runway systems with meadow voles, Microtus pennsylvanicus (Wilson et al, 1999).

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).

None known.

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

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