One true lemming, as well as several closely related species commonly called lemmings, live in Alaska. Distinguishing one from the other, or even lemmings from voles, is difficult. Many of the small rodents in the north have a similar appearance, especially during the summer months. The information below will help to identify lemming species in the field, but positive identification can be made only with the help of a mammology text or field guide which gives detailed information on tooth structure and skull conformation.
The brown lemming, Lemmus sibiricus, is the only true lemming in Alaska. Brown lemmings inhabit open tundra areas. Their principal summer foods are tender shoots of grasses and sedges. During the winter they eat bark and twigs of willow and dwarf birch. They also are known to be cannibalistic during times of food stress.
True lemmings, the largest of the various lemming species, range from 4 to 5½ inches (100 to 135 mm) in length, including a 1 inch (12 to 26mm) tail. Adults weigh from just over an ounce to 4 ounces (40 to 112 g) but average 2¾ ounces (78 g). These lemmings are heavily furred, grayish or brownish above and buffy beneath, and are stockily built. They are well-adapted for their rigorous climate with short tails and ears so small they are almost hidden by fur. They are active both day and night and tend to follow the same routes from nests to feeding spots until their living area becomes a network of trails a couple of inches below the snow or land surface. Winter nests are commonly found in lowland areas where the snow, a good natural insulation, is deepest.
Breeding apparently begins before the animals are full grown. It may occur all winter under the snow but is usually restricted to the brief summer, June to September. The average litter size is 7.3 young, and young lemmings weigh only a little over one-tenth of an ounce (3 g) at birth. They open their eyes at 11 days and can walk at 15 days.
Lemmings are known for their wide fluctuation in population numbers, reaching peak abundance in some areas every three to five years. The causes of population fluctuations are unclear, although some combination of predation, food quantity and quality, weather, or genetic change in individuals making up the population is probably involved. Actual migrations do not occur, although some lemmings may move into marginal or unsuitable areas during periods of population increase. This probably explains occasional sightings of lemmings on sea ice well beyond land.
The collared lemming (Dicrostonyx groenlandicus), not a true lemming by genus, frequents dry, sandy, or gravelly areas above the timber line and is, for some, the most interesting of the lemmings because of its peculiar adaptations to winter. It is the only true rodent that turns white in the winter. Its thick white winter coat is used by the Eskimos for garment trimming. The collared lemming also grows enlarged claws, rather like snow shovels, on the third and fourth digits of its forefeet. The winter claws are used to dig through the wind-packed snow common in its arctic habitat. There have even been reports of lemmings drilling through the walls of igloos! The claws are slowly worn away and by spring all claws have the same shape. These animals also build extensive runways and nesting areas.
Collared lemmings average a little over 14 ounces (40 g) in weight and are about 4¾ inches (120 mm) long. Their appearance is much like that of true lemmings except for definite dark lines or stripings from the top of the head along the middle of the back and on the sides of the head. Like true lemmings they consume mostly plants, although it is possible that they eat insects and meat when available.
When sexually mature, females weigh slightly more than an ounce (30 g). Mating may occur as early as January but usually takes place from March to September. During the height of the summer breeding season nearly all females are pregnant, and each may have up to three litters a year with an average of 4½ young per litter. Few collared lemmings live beyond 1 year of age. With this rapid breeding and short life cycle, it is common for 30 percent of the collared lemming population to die every two weeks.
The northern bog lemming, Synaptomys borealis, is native to the area all along the Pacific coast of Alaska. They seem to occupy cold bog or spring areas, but they are also found near rocky cliffs.
They are the smallest of the lemmings in size, with a mean weight of just a bit more than an ounce (33 g) and a head and body length around 4 inches (100 mm). Their general coloration is a grizzled brown above and soiled white underneath. Northern bog lemmings occupy somewhat warmer climates than the other lemmings, and their fur is not so thick. Their powerful jaws may be an indication that they gnaw through tangles of roots, moss, and soil, but they feed mainly on green parts of low vegetation and probably on slugs and snails.
The breeding pattern of the northern bog lemming is much like that of the other lemmings, with most breeding occurring during the summer and litters averaging three per year. They also make extensive runways and tunnels, though they occasionally occupy and use those of other small mammals.
All of the lemmings are staple prey for many larger animals occupying their ranges, including weasels, arctic foxes, wolves, wolverines, snowy and short-eared owls, rough-legged hawks, peregrine falcons, glaucous gulls, and jaegers. Perhaps one of the most fascinating aspects of the lemming is its capability for survival in its predominantly harsh environment. To come across the intricately-patterned and well-traveled raceways of a group of lemmings while traveling across apparently barren frozen ground gives one a sense of the wonderful and delicate balance of life in all climes.
Text: Paul Whitney
Illustration: Bill C. Ray
Revised and reprinted 1994
