Marmota broweri
Alaska marmot

Alaska marmots are found in the Neartic region of the world. This species has an isolated range in the Brooks Mountains of northern Alaska. Marmota broweri has a patchy distribution because suitable habitat is widely scattered within its range. (Wilson and Ruff, 1999)

Within the Brooks Mountain range, Alaska marmots occupy boulder fields, rock slides, and rock outcroppings. M. broweri utilizes the subsurface space provided by the rocks and boulders to create its living space by burrowing into the permafrost soil. Tundra vegetation surrounds the rocks where M. broweri makes its home. Usually, each den has an observation post, such as a tall rock or cliff edge, within ten meters of its entrance. A marmot will perch on this lookout and keep an eye out for predators. (Wilson and Ruff, 1999)

M. broweri is a typical marmot, with coarse hair over a heavy body. The neck is short, the tail is bushy, the legs and feet are powerful, and the claws are strong and well suited to digging. They have typical rodent incisors that are sharp and chisel-like and grow indefinitely throughout life. The thumbs of the front limbs have a flat nail, whereas the other digits have claws.

Adult Alaska marmots have solid black fur on the dorsal surface of the head and the nose. The rest of the pelage is generally dark, blending perfectly with the dark lichens on the rock fields of its local environment.

Body size fluctuates during the year because of hibernation. A marmot leaves its winter sleep very thin but quickly gains weight, with 20% of its body weight being fat stored for its long hibernation at the end of summer. M. broweri displays slight sexual dimorphism. The average total length of adult males being 605 mm and the average weight being 3.63 kg. In comparison, adult females have an average total length of 579 mm and average weight of 3.18 kg. (Wilson and Ruff, 1999)

Life span is not known, but it is believed to be similar to that of the related species, M. marmota, which is thirteen to fifteen years. (Nowak, 1983)

Alaska marmots are social creatures and can live in colonies of up to fifty animals all sharing an immense burrow system. Usually, each marmot maintains its own den, but young stay with the mother and the father's den is nearby. The size of the colony affects the amount of energy and time that individual marmots must expend in watching for predators. Sentry duty rotates among animals, and in larger colonies, less time needs to be spent by individual marmots performing that task. The sentries alert all to danger at the sight of an eagle or other potential predator. Sheep and caribou do not alarm the sentries.

M. broweri are carefully groomed animals that enjoy sunbathing. Wind is an important part of the climate from the marmot’s perspective because it controls the presence of insects that annoy marmots. On days when the air is thick with mosquitoes, Alaska marmots don’t even leave their dens (Bee, 1956).

Alaska marmots is active until the first snowfalls in late August. At that point, marmots retreat to their dens in family units to huddle together and hibernate through the winter. The last animal in, usually an adult male, plugs the entrance from the inside with hay, earth, and stone. While the animals hibernate their heart rates and respiratory rates slow. Their body temperature is lowered but is sustained above freezing, even when it well below zero outside. The average body temperature of a hibernating marmot is between 4.5 and 7.5 degrees Celsius. Their hibernation is not continuous and every three or four weeks a marmot awakens to urinate and defecate. (MacDonald, 1999)

The tundra vegetation that grows on the sides of mountains is the primary source of nutrition available to M. broweri. In the early mornings and late afternoons, Alaska marmots can be seen grazing in the areas immediately surrounding their dens. The grasses, forbs, fruits, grains, legumes, and the occasional insect that marmots eat are all relatively low in nutritional value. These animals must therefore consume large quantities in order to put on weight for hibernation. Near the end of summer, the contents of am Alaska marmot’s digestive tract account for a fourth to a third of the animal’s total weight. (Nowak, 1983)

Marmots post sentries to look out for predators. Common predators of Alaska marmots are wolverines, wolves, grizzly bears, and eagles. At the sight of a predator, the sentry shrieks an alarm and all members of the family or colony retreat into their dens. Grizzly bears are able to dig marmots right out of their dens, so building dens under large boulders is important to Alaska marmots. Eagles are the principal predators of juveniles. (Wilson and Ruff, 1999)

The mini-ecosystem to which M. broweri belongs would be the rock pile. Voles scurry in-between the rocks, wolverines range along the outside of the rocks, and caribou graze over the rocks. The marmot helps to enrich the soil with its uneaten food, nesting material, fecal pellets, and excavated soil. (Nowak, 1983) It is also likely that the population of marmots affects populations of predators in proportion to the importance of marmots in the predators’ diets.

No negative effects of this species on humans have been reported.

Historically, M. broweri were occasionally hunted by the native people of Alaska for meat. More often, marmots were harvested for their thick fur. An Eskimo hunter would spend all summer hunting marmots to make a parka, as it takes about twenty marmot skins to make one parka. The marmots can be shot, but were often caught in rock fall traps. (Bee, 1956)

M. broweri is widely spread throughout the Brooks Range but its population densities are usually low. Alaska marmots may be hunted by natives, but not to the point of endangerment. The marmot population is stable within its range. (Wilson and Ruff, 1999)

For many years M. broweri existence as a unique species was questioned. It was believed to be a subspecies of the Hoary marmot, M. caligata (Hall and Gilmore, 1934). Chromosome mapping revealed that they are separate species (Rausch, 1965).