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Marmota olympusOlympic marmot

By Erin Benton

Geographic Range

Olympic marmots, Marmota olympus, are found almost exclusively in the Olympic National Park on the Olympic Peninsula in the state of Washington (USA). (Barash, 1973)

Habitat

Olympic marmots primarily occupy sub-alpine and alpine meadows as well as talus slopes. The are generally found at elevations of 1,500 to 1,750 m but have been observed at elevations as low as 3 m and as high as 1,990 m. The alpine meadows and subsequent area include avalanche lilies (Erythronium montanum), mountain buckwheat (Polygonum bistortiodes), as well as sub-alpine lupine (Lupinus subalpinus). This region is characterized by large amounts of rainfall, averaging 75 cm per year. Most of the annual precipitation falls in the form of snow. (Barash, 1973)

  • Range elevation
    30 to 1,990 m
    98.43 to ft
  • Average elevation
    1,500 to 1,750 m
    ft

Physical Description

Olympic marmots are, on average, larger than other marmots. They are approximately 7% longer than Marmota caligata and Marmota vancouverensis. Olympic marmots exhibit sexual dimorphism; on average, adult males weigh 9.3 kg while adult females weigh 7.1 kg. Body mass is seasonally dependent in both sexes, and individuals lose about 50% of their total body weight during the 7 to 8 months of winter hibernation. When they emerge from hibernation, adult males weigh an average of 4.1 kg while females weigh an average of 3.1 kg. Both young males and females (1 to 2 years in age) lose approximately the same percentage of body mass, though their total mass is lower than that of adults. (Barash, 1973; Edelman, 2003)

Olympic marmots have 2 types of fur covering their body: soft dense underfur that keeps them warm and coarser outer fur. Their ears, tail, face, and legs are also covered in fur. They are generally brown with intermixed white, but pelage color is often seasonally dependent. On emerging from hibernation, their fur is yellow/brown in color. Infants are dark gray in color while yearlings are grayish brown with some lighter patches of fur. Olympic marmots molt twice during the year. The first molting occurs in June when two black patches of fur develop on the back of the shoulders of an adult and subsequently spread to the rest of the body. The second molting is thought to occur during during hibernation, as adults emerge in the spring with lighter fur. While Olympic marmots are similar in appearance to hoary marmots and Vancouver marmots, hoary marmots have black feet and a black spot on their head, and Vancouver marmots are almost completely black in appearance. (Barash, 1973; Edelman, 2003)

  • Sexual Dimorphism
  • male larger
  • Range mass
    3.1 to 11.0 kg
    6.83 to 24.23 lb
  • Range length
    670 to 750 mm
    26.38 to 29.53 in

Reproduction

Copulation of Olympic marmots begins immediately following emergence from hibernation. Attempts are initiated by both sexually mature males and females in a number of different ways. Greetings often begin with a sniff of the nasal or genital area, and nasal-nasal or nasal-genital contact commonly occurs. If the female is parous (having already produced a litter), most attempts to mount will be successful and the pair will copulate. Successful mountings of parous females peaks in frequency at 11 to 20 days after emerging from hibernation. Non-parous females (those who have not yet had offspring) show more aggressive behavior and may chase or initiate fights with approaching males. Olympic marmots are polygynous. ("Notes and Discussion - Female Olympic Marmots (Marmota olympus) Reproduce in Consecutive Years", 2007; Barash, 1973)

In Olympic marmots, estrus (physiological changes that signal reproductive availability) occurs about two weeks after adults emerge from hibernation. Emergence occurs during early to mid-May. After a gestation period of 4 weeks, females give birth to a litter of 3 to 5 offspring. Juveniles weigh between 1.2 and 1.6 kg at birth (average 1.55 kg). They are weaned around 10 weeks of age and reach independence around 2 years of age. Olympic marmots reach sexual maturity between 2 and 4 years of age. ("Effects of Tourists on Behavior and Demography of Olympic Marmots", 2006; Barash, 1973)

Sexually mature female Olympic marmots breed every other reproductive season. Reasons for the skipping of a reproductive season are uncertain. A dominant theory suggests that, due to the short period of time between the end of lactation and beginning of hibernation (6 to 8 weeks), adult females weigh less than males and sexually immature females when entering hibernation. This lower ratio of mass to fat can result in mortality during the 8-month hibernation period. Because they are unable to amass enough fat to reproduce each year, they skip reproductive seasons. Another theory contributes reproductive skipping to female aggression establishing dominance. In one study, among colonies of alpine marmots, aggression of mature females caused stress and hormonal changes in subdominant females, preventing them from successfully reproducing. ("Effects of Tourists on Behavior and Demography of Olympic Marmots", 2006; "Notes and Discussion - Female Olympic Marmots (Marmota olympus) Reproduce in Consecutive Years", 2007; Barash, 1973)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • viviparous
  • Breeding interval
    Olympic marmots usually breed every other year.
  • Range number of offspring
    3 to 5
  • Average gestation period
    4 weeks
  • Average weaning age
    10 weeks
  • Average time to independence
    2 years
  • Range age at sexual or reproductive maturity (female)
    2 to 4 years
  • Range age at sexual or reproductive maturity (male)
    2 to 4 years

Mother Olympic marmots provide considerable care to their young until they reach independence. Infants do not emerge from the burrow until 1 month after birth. The mother spends most of her time near the burrow and leaves only for short periods of time, at most 30 minutes, to forage. Once the infants emerge, the mother stays within yards of her offspring, and she doe not let them venture farm from the burrow. Within several weeks, offspring have become sufficiently independent to forage for themselves. ("Notes and Discussion - Female Olympic Marmots (Marmota olympus) Reproduce in Consecutive Years", 2007; Barash, 1973)

  • Parental Investment
  • female parental care
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Olympic marmots generally live between 2 and 6 years in the wild. Females that reproduced during the summer have a higher mortality than those that do not. This is attributed to their parental investment; these females spend more time foraging for their young than for themselves. As a result, they can either spend time later in the summer building up their fat supply for winter or hibernate with a lower body mass. By foraging later in the year, females risk mortality through exposure to winter elements. By hibernating with a lower body mass, they risk starvation. (Barash, 1973)

  • Typical lifespan
    Status: wild
    2 to 6 years

Behavior

Olympic marmots are highly social and live in colonies usually consisting of a male and 2 to 3 females in addition to their infants, and 1- and 2-year old offspring. They use habitual social greetings as a means of identifying individuals within a colony. Social greetings differ from reproductive greetings; social greetings generally begin with a nose-to-nose or nose-to-cheek interaction between individuals. The greeting may end at this point, however Olympic marmots are also known to engage in more extensive greeting rituls which may include inter-locking of the teeth and chewing of the ear and/or neck. (Barash, 1973; Edelman, 2003)

Olympic marmots are diurnal, and their activity patterns vary with time of year, time of day, and weather. In the early summer (May), when there is still dense snow cover, they have restricted feeding areas. During the summer months of June, July and August, adults forage and interact with other individuals during the morning and evening, and they spend most of the day inside the burrow. During the summer months, Olympic marmots are considerably less active during rain or snowfall or in the presence of heavy fog cover. By mid-September, they have entered their burrows to begin winter-hibernation, which lasts 8 months. (Barash, 1973; Edelman, 2003)

  • Average territory size
    700 m^2

Home Range

The home range of Olympic marmots is typically five acres. (Barash, 1973)

Communication and Perception

Olympic marmots communicate through physical interaction, vocal, and olfactory methods. Physical social and mating greetings are described in previous sections. They also use chemical markers excreted from a gland in the cheek to mark territory. These marks are most often made on rocks or shrubs. Type and length of vocal calls vary with different external stimuli; vocal responses to an unfamiliar noise or smell differs from vocal responses to the presence of a predator. Calls of an ascending pitch, which have been interpreted as distress calls, include a "chip" or "yell" lasting approximately half a second. Length of calls is negatively correlated with level of distress: calls are shorter when the treat is immediate or realized. Play fighting is characterized by teeth chattering as well as low growls and high pitched "yips." (Barash, 1973; Blumstein, 1999)

Food Habits

Olympic marmots are folivorous, consuming meadow flora species found on the Olympic Peninsula including avalanche lilies (Erythronium montainum), sub-alpine lupine (Lupinus subalpinus), mountain buckwheat (Polygonum bistortoides), Arenaria capillaris and harebells (Campanula rotundifolia) along with other grasses, flowers and roots. Olympic marmots have also been known to scavenge small, dead animals such as Townsend's chipmunks when snow is present and access to flora is limited. Olympic marmots rely on snow and glacial melt for their water supply. When these sources become unavailable, Olympic marmots are thought to obtain most of their water from the vegetation they consume, from water within the plant as well as dew on the foliage. (Barash, 1973; Edelman, 2003)

  • Plant Foods
  • leaves
  • roots and tubers
  • flowers

Predation

Olympic marmots are often preyed upon by large terrestrial mammals and may also be prayed upon by avian raptors. Primary predators include cougars and coyotes. Black bears, golden eagles, and bobcats have also been observed preying on the Olympic Marmot. When a large predator is spotted in the area, members of the colony produce alarm calls. (Barash, 1973; Edelman, 2003)

Ecosystem Roles

Olympic marmots feed on the most common flora of the Olympic National Park high meadows, and their generalized feeding habits keep populations of dominant flora species in the meadows at ecologically healthy levels. The result is an overall increase in species richness in the immediate area. Olympic marmots also act as hosts to fleas (Oropsylla eatoni and Oropsylla spenceri spenceri) as well as certain cestodes (tapeworms) such as Diandrya composita. (Barash, 1973; Del Moral, 1984; Edelman, 2003)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

There are no known direct positive effects of Olympic marmots on humans. Because they feed on a variety of flora and are consumed by a variety of predators, they help maintain a thriving ecosystem in the meadows of the Olympic National Park.

Economic Importance for Humans: Negative

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

Conservation Status

Olympic marmots are considered a speices of least concern by the ICUN. Although populations are decreasing and they have a limited geographic range, they are protected by laws that protect the Olympic National Park.

Contributors

Erin Benton (author), University of Oregon, Stephen Frost (editor), University of Oregon, Gail McCormick (editor), Animal Diversity Web Staff.

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

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.

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

fossorial

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

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.

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.

native range

the area in which the animal is naturally found, the region in which it is endemic.

polygynous

having more than one female as a mate at one time

sedentary

remains in the same area

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.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

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

2006. Effects of Tourists on Behavior and Demography of Olympic Marmots. Conservation Biology, 21/4: 1070-1080.

2007. Notes and Discussion - Female Olympic Marmots (Marmota olympus) Reproduce in Consecutive Years. The American Midland Naturalist, 158/1: 221-224.

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

Barash, D. 1973. The Social Biology of the Olympic Marmot. Animal Behaviour Monographs, 3/3: 172-245.

Blumstein, D. 1999. Alarm Calling in Three Species of Marmots. Behavior, 136/6: 731-757.

Del Moral, R. 1984. The Impact of the Olympic Marmot on Subalpine Vegetation Structure. American Journal of Botany, 71/9: 1228-1236.

Edelman, A. 2003. Marmota Olympus. Mammalian Species, 736: 1-5.

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