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Marmota broweriAlaska marmot

By Andrea Lazzari

Geographic Range

Alaska marmots (Marmota broweri) can only be found in the Nearctic region of the world. Hall and Gilmore (1934) reported that they have a very limited range in Northern Alaska, along the Arctic coast. Later work done by Slough and Jung (2007) suggests that the range of the Alaska marmot should include only the Brooks Range mountains in northern Alaska. They speculate that Alaska marmots might also occur in the Yukon, but there is currently no evidence to support this claim. (Hall and Gilmore, 1934; Slough and Jung, 2007)

Habitat

Alaska marmots have a scattered distribution, because they prefer a distinct habitat (Wilson and Ruff, 1999). They inhabit boulder fields and rocky outcrops on the slopes and in the valleys and canyons of the Brooks Mountains (Bee and Hall, 1956). They prefer particularly boulder fields and rocky outcrops where there are large enough spaces for them to dig dens between rocks. The entrances to the dens are usually protected by boulders, which helps to shield Alaska marmots from various predators. There are usually one or more observation points on top of the boulders near the den entrance, where Alaska marmots search for predators before beginning to forage (Wilson and Ruff, 1999). It is rare to find Alaska marmots living in boulder fields that are far from productive foraging sites (Bee and Hall, 1956). (Bee and Hall, 1956; Wilson and Ruff, 1999)

  • Range elevation
    990.6 to 1219.2 m
    3250.00 to 4000.00 ft
  • Average elevation
    1127.76 m
    3700.00 ft

Physical Description

Alaska marmots are distinguished from other species of marmots by the black fur on top of their head, extending from the tip of the nose to the neck. These marmots have coarse hair that ranges in color from brown and black to white. Their back usually has brown hair, with a lighter brown underneath the black-tipped guard hairs. Their dark fur provides useful camouflage against the foliage and boulder fields in their habitat. Alaska marmots are fairly large (males are slightly larger than females) and heavy-bodied, with a short neck and a slightly flattened, bushy tail. The tail usually accounts for a third to a fifth of the total body length. Alaska marmots have black lips and black feet. The front feet sometimes have white markings. They have no fur on their palms (which have five pads) or their soles (which have six pads). Each limb has five digits with claws. The claws of the forelimbs are thick and curved for digging. The thumbs of the forelimbs have a flattened nail instead of a claw. Their legs are short, thick, and muscular. Alaska marmots have five pairs of mammae, for a total of ten. The eyes are small and circular and the furry ears are broad, short, and rounded. Alaska marmots have cheek pouches, but they are vestigial. Due to hibernation, weight varies across seasons, but they are able to gain weight quickly after emerging from hibernation. Alaska marmots experience one molt during the summer, but it does not seem to have a uniform pattern (Bee and Hall, 1956; Hubbart, 2011; Wilson and Ruff, 1999). (Bee and Hall, 1956; Hubbart, 2011; Wilson and Ruff, 1999)

Alaska marmots are rodents, and so have the typical, chisel-like ever-growing incisors (Hubbart, 2011). Based on figures in Bee and Hall (1956), the cheekteeth of Alaska marmots have high ridges that fan out. Hubbart (2011) reports the dental formula of I 1/1, C 0/0, P 2/1, M 3/3 = 22. Compared to other species of marmots, Alaska marmots have a larger postorbital width and longer tympanic bullae. These marmots also have a short, deep angular process. The rostrum is fairly long and the postorbital process is wide. The zygomatic arches are complete and quite rounded. The sagittal crest and lambdoidal ridge are both fairly prominent (Hubbart, 2011). (Bee and Hall, 1956; Hubbart, 2011)

  • Sexual Dimorphism
  • male larger
  • Range mass
    2.5 to 4 kg
    5.51 to 8.81 lb
  • Average mass
    3.41 kg
    7.51 lb
  • Range length
    539 to 652 mm
    21.22 to 25.67 in
  • Average length
    592 mm
    23.31 in

Reproduction

Alaska marmots live in family groups, or colonies, consisting of males and females. A male will usually mate with one or more females living in dens near his own (Hubbart, 2011; Wilson and Ruff, 1999). Mating is stimulated by pheromones released from the anal scent glands of both males and females. Copulation usually takes place inside the den before Alaska marmots emerge from hibernation in the spring (Hubbart, 2011). There is no information available on the pre-copulation behavior of Alaska marmots. However, in the closely related Olympic marmots, these behaviors include sniffing, chasing, and fighting. Alaska marmots may exhibit similar behaviors (Barash, 1989). (Barash, 1989)

Alaska marmots breed once a year around the time that they begin to emerge from hibernation. This is usually early in the month of June. Gestation time is five to six weeks and a female can have a litter of three to eight young, averaging usually four or five. Before giving birth, a female closes off her den so that she can be alone. Her litter is born altricial, but by six weeks old, the young are able to leave the den and explore outside. The timing of weaning of the litter is unknown; however, Hubbart (2011) reports that it may be at six weeks when the young are able to leave the den, as this is the common pattern for other species of marmot. (Hubbart, 2011)

During their first year of life, juvenile Alaska marmots produce three fur coats, the third being similar to that of adults. Juveniles live and hibernate with their parents for two years, at which time they become independent adults. At three years of age, both males and females become sexually mature (Hubbart, 2011). (Hubbart, 2011)

  • Breeding interval
    Alaska marmots breed once yearly.
  • Breeding season
    Alaska marmots mate in June, after emerging from dens at the end of hibernation period.
  • Range number of offspring
    3 to 8
  • Average number of offspring
    4
  • Range gestation period
    5 to 6 weeks
  • Average time to independence
    2 years
  • Average age at sexual or reproductive maturity (female)
    3 years
  • Average age at sexual or reproductive maturity (male)
    3 years

Both male and female Alaska marmots raise and protect their litter. This investment lasts for two years, at which time the juveniles become independent of their parents. During those two years, both parents provide shelter and protection year round (Hubbart, 2011). (Hubbart, 2011)

Lifespan/Longevity

The lifespan of Alaska marmots are unknown. However, it is likely similar to that of related species, which are expected to live between 13 to 15 years. Nothing is known about the captive lifespan of Alaska marmots (Hubbart, 2011). (Hubbart, 2011)

  • Typical lifespan
    Status: wild
    13 to 15 years

Behavior

Alaska marmots are social and live in colonies of up to fifty individuals. However, each marmot has its own den (Hubbart, 2011). The location of dens and burrows in boulder fields is chosen in an attempt to exclude large predators, such as grizzly bears, which are not able to reach the animals between the rock crevices (Bee and Hall, 1956). It has been suggested that summer burrows are at a lower elevation than winter burrows; however, there is not much evidence to support this hypothesis (Wilson and Ruff, 1999). (Bee and Hall, 1956; Hubbart, 2011; Wilson and Ruff, 1999)

Time spent outside of the den is usually devoted to one of two activities: foraging or lookout duty. All adult individuals in a colony spend time on lookout duty, during which they stand on observation points around the dens looking for predators. This allows the other individuals in the colony to forage relatively safely. When a predator is spotted, the marmot on lookout duty will give an alarm call, which causes the colony members to retreat back into their dens. There is evidence that alarm calls vary slightly depending on the type of predator spotted. Individuals outside of their dens who are not on lookout duty or foraging are usually either sunbathing or grooming themselves (Hubbart, 2011). (Hubbart, 2011)

The behavior of Alaska marmots is strongly influenced by mosquitoes. During the summer months in Alaska, mosquitoes can be extremely abundant. This causes individuals to remain inside their den on warm, sunny days when the mosquitoes are out in vast numbers. Alaska marmots are most active on cool, cloudy, windy days when the mosquitoes are not active (Hubbart, 2011; Wilson and Ruff, 1999). (Hubbart, 2011; Wilson and Ruff, 1999)

Mating behaviors of Alaska marmots are stimulated by pheromones released by anal scent glands in males and females (Hubbart, 2011). (Hubbart, 2011)

Alaska marmots hibernate for the majority of the year. Hibernation begins around the first major snow storms in late August and early September and continues until the snow begins to melt and food becomes available in early June (Hubbart, 2011; Wilson and Ruff, 1999). When hibernation begins, Alaska marmots block den entrances with vegetation, stones, soil, and feces. Individuals will huddle in groups during hibernation. During this time, heart and respiratory rates decrease and body temperature decreases to a temperature between 4.5 and 7.5 degrees Celsius. Hibernation in Alaska marmots is discontinuous. Individuals awaken every three to four weeks to urinate and defecate, after which hibernation is resumed (Hubbart, 2011). (Hubbart, 2011; Wilson and Ruff, 1999)

Home Range

There is no information available on the home range or territory size of Alaska marmots. However, territory size of the closely related yellow-bellied marmot is 0.67 hectares (Armitage, 1974). (Armitage, 1974)

Communication and Perception

Communication in Alaska marmots, specifically alarm calling, is particularly well studied. This involves both a well-developed sense of hearing and a well-developed sense of sight. All adult Alaska marmots spend time on sentry duty, standing on top of observation points on the lookout for predators. When a predator is spotted, the marmot on sentry duty will emit an alarm call, which alerts the other individuals outside of the dens of the potential danger, causing them to retreat back inside their respective dens. Bee and Hall (1956) described the call as being low pitch and slurred. It is important to note that only predatory animals stimulate alarm calling, and that these calls can vary slightly based on the type of predator. For example, eagles stimulate approximately four consecutive calls, while humans elicit one to two. Predators far away from the colony result in a continuous call, though it seems less urgent (Bee and Hall, 1956). (Bee and Hall, 1956)

Alaska marmots do not seem to benefit from the alarm calls of other species. However, it is possible that other species benefit from the alarm calls of Alaska marmots (Bee and Hall, 1956). (Bee and Hall, 1956)

Food Habits

Alaska marmots are primarily herbvivorous, eating mostly the tundra vegetation growing near their burrows. They can also be classified as folivorous, granivorous, frugivorous, insectivorous, and omnivorous, due to the grasses, forbs, grains, legumes, fruits, and few insects in their diet, respectively. Due to the low nutritional quality of their food, Alaska marmots must spend a great deal of time foraging and eat a large quantity of food. This is why they often create dens and burrows very near their food sources. By the end of the summer, it is not uncommon for the contents of the stomach and digestive tract of Alaska marmots to account for up to one third of its total body weight. Alaska marmots compete indirectly with animals such as Dall's sheep, caribou, and other small rodents for food (Hubbart, 2011; Wilson and Ruff, 1999). (Hubbart, 2011; Wilson and Ruff, 1999)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • fruit
  • flowers

Predation

Alaska marmots are preyed on by a number of species. Eagles, including the golden eagle, frequently prey upon juvenile marmots. Grizzly bears, wolves, and wolverines all pose a threat to juvenile and adult Alaska marmots (Wilson and Ruff, 1999). (Wilson and Ruff, 1999)

Alaska marmots exhibit two anti-predator strategies. Because this is a social species, individuals take turns on lookout duty, communicating to other colony members with alarm calls when they spot a predator nearby. The observation points near den entrances are used by marmots on lookout duty (Bee and Hall, 1956). Observation points are also used by individuals outside of the den to search for predators before beginning to forage (Wilson and Ruff, 1999). The sounding of an alarm call causes group members to retreat back into their dens (Hubbart, 2011). Bee and Hall (1956) claimed that the alarm call of Alaska marmots can vary slightly depending on the type of predator and its location. They also observed that non-predator animals do not cause any kind of call. The fur color of Alaska marmots provide camouflage against the foliage of the mountainsides and boulder fields (Hubbart, 2011). (Bee and Hall, 1956; Hubbart, 2011; Wilson and Ruff, 1999)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Alaska marmots are an important prey species for many animals, including grizzly bears, wolves, wolverines, and eagles Accipitridae (Hubbart, 2011). Alaska marmots are also a host species for a variety of parasites, including species of fleas, nematodes, and cestodes (Rausch and Rausch, 1971; Hubbart, 2011). Alaska marmots play an important role in soil enrichment and aeration. Digging dens and burrows helps to aerate the soil, while uneaten food, nesting material, and fecal matter help enrich it (Hubbart, 2011). (Hubbart, 2011; Rausch and Rausch, 1971)

Commensal/Parasitic Species
  • fleas (Oropsylla silantiewi)
  • cestode (Catenotaenia reggiae)
  • cestode (Diandrya composita)
  • nematode (Ascaris laevis)

Economic Importance for Humans: Positive

Alaska natives have been known to hunt Alaska marmots for meat, and more often, for fur. The most common method used to hunt the animal is with rock fall traps (Hubbart, 2011). It has been reported that the fur of Alaska marmots is fairly valuable, with an average profit of six to eight dollars per pelt (Bee and Hall, 1956). (Bee and Hall, 1956; Hubbart, 2011)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse affects of Alaska marmots on humans.

Conservation Status

While they has a limited range and a scattered population distribution, Alaska marmots are not threatened and appear to have a stable population size. Hunting does not seem to have a significant or detrimental affect on the population (Wilson and Ruff, 1999). (Wilson and Ruff, 1999)

Contributors

Andrea Lazzari (author), Michigan State University, Barbara Lundrigan (editor), Michigan State University, Laura Podzikowski (editor), Special Projects.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

fossorial

Referring to a burrowing life-style or behavior, specialized for digging or burrowing.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

soil aeration

digs and breaks up soil so air and water can get in

tactile

uses touch to communicate

terrestrial

Living on the ground.

tundra

A terrestrial biome with low, shrubby or mat-like vegetation found at extremely high latitudes or elevations, near the limit of plant growth. Soils usually subject to permafrost. Plant diversity is typically low and the growing season is short.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Armitage, K. 1974. Male behaviour and territoriality in the Yellow-bellied marmot. Journal of Zoology, 172: 233-265.

Barash, D. 1989. Marmots: Social Behavior and Ecology. California: Stanford University Press.

Bee, J., E. Hall. 1956. Mammals of Northern Alaska. Lawrence, Kansas: University of Kansas.

Benton, E. 2011. "Marmota olympus" (On-line). Animal Diversity Web. Accessed March 07, 2012 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Marmota_broweri.html.

Hall, E., R. Gilmore. 1934. Marmota caligata broweri, a new marmot from northern Alaska. The Canadian Field-Naturalist, 48: 57-60.

Hubbart, J. 2011. Current Understanding of the Alaska Marmot (Marmota broweri): A Sensitive Species in a Changing Environment. Journal of Biology and Life Sciences, 2: 6-13.

Rausch, R., V. Rausch. 1971. The Somatic Chromosomes of Some North American Marmots (Sciuridae), with Remarks on the Relationships of Marmota browerii Hall and Gilmore. Mammalia, 35: 85-101.

Slough, B., T. Jung. 2007. Diversity and Distribution of the Terrestrial Mammals of the Yukon Territory: A Review. The Canadian Field-Naturalist, 121: 119-127.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington: Smithsonian Institution Press.

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