Synaptomys cooperi
southern bog lemming

Southern bog lemmings are found in eastern North America, from southeast Canada to western Minnesota, down to southwest Kansas and east to northeast North Carolina.

Synaptomys cooperi occurs mainly in sphagnum bogs, as its common name suggests, but it may also occur in grasslands, and in Canada it occurs in coniferous or deciduous forests. In Michigan, it can be found in clear cuts, old fields, or upland woods. Occurrence within the larger geographic range is patchy--it tends to occupy isolated areas. This is thought to be due to competition with meadow voles.

Southern bog lemmings are small voles, weighing 20 to 50 grams and measuring 110 to 140 mm in total length. The dorsal pelage ranges in color from a chestnut to dark brown that has a grizzled appearance. The venter is silver-gray. Females of this species have 6 mammae, which differentiate it from its closest relative, Synaptomys borealis, which have 8 mammae. The orange incisors are broad and longitudinally grooved. The tail is short, barely longer than the hind foot.

Breeding occurs in all seasons, especially where food is not limiting. Most young are born between April and September. Females are polyestrous--one captive bore 6 litters in 22 weeks. Wild females produce 2 or 3 litters per year. Gestation lasts from 23 to 26 days. Mean litter size is 3 but can range from 1 to 8. Males can reach sexual maturity in 5 weeks.

Southern bog lemmings weigh 3.7 grams at birth. Young are born with no fur, closed eyes, and with the ear pinnae folded over. Claws are apparent at birth. By the end of the first week, the young are well furred. The female nurses her young for three weeks.

Wild southern bog lemmings usually do not live for more than a year. In captivity, they may live up to 29 months.

Not much is known about social interactions of southern bog lemmings. Population density can range from 6 to 35 individuals per hectare. Synaptomys cooperi does not hibernate and can be active any time of day or night, but is mostly nocturnal. It makes runways and tunnels or uses those of other species. It also builds nests from dry grasses which are concealed under stumps or sphagnum mounds.

There is thought to be intraspecific communication in the form of scent marking from anal secretions. Vocalizations are squeaks.

Southern bog lemmings eat mostly vegetation such as grasses, sedges, mosses, fruits, fungi, bark and roots. Bog lemmings snip stems near the ground to get access to the upper parts. Often surrounding vegetation prohibits the stems from falling, so additional snips must be made. Some invertebrates such as slugs and snails are also taken. The jaws are powerful and thought to be used extensively for gnawing.

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

Southern bog lemmings have important ecosystem roles as food for a number of predators (see above) and as competitors with other small rodents, such as meadow voles.

Once very common, numbers seem to be declining as a result of habitat destruction and the overgrowth of bogs. One subspecies, Synaptomys cooperi helaletes, is thought endangered and possibly extinct. Other subspecies also appear to be threatened.