Olympic marmot
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Sciuridae
Genus:	Marmota
Subgenus:	Petromarmota
Species:	M. olympus
Binomial name
Marmota olympus (Merriam, 1898)
Range of Olympic Marmots

The Olympic marmot, Marmota olympus, is a rodent in the squirrel family, Sciuridae. They are close relatives of the hoary marmot. This species is exclusively indigenous to alpine and subalpine meadows and talus slopes on the Olympic Peninsula in the U.S. state of Washington. For this reason, the Olympic marmot was declared Washington's state endemic mammal in 2009.^[2]

This species was first regarded as a subspecies of M. marmota by Clinton Hart Merriam, an American entomologist, ethnographer, ornithologist, and zoologist, in 1898.^[3] It was later described as the distinct species, Marmota olympus, by taxonomists such as Jones in 1992, Hoffman in 1993, and Thorington in 2005.^[1] They renamed it with the term olympus, meaning olympic in Greek, because this species is endemic to the Olympic Peninsula of Washington state. Before becoming considered native to only this peninsula, they were thought to have originated as an isolated relict population in the Pleistocene ice-free refugia. Since then, it has grown to show the highest rate of sexual dimporphism of all species of marmots. The Olympic marmot deviates from the typical Petromarmota subgenus in the large shape of its mandible, in differences of the dorsal region, and having 40 chromosomes instead of 42, all of which are characteristics that resemble the genus Marmota. These disparities are also evident in the Vancouver Island marmot, which evolved differently, but also live in small populations in restricted areas.^[4]

This rodent is about the size of a house cat, weighing 3.1 kg (6.8 lb) to 11 kg (24 lb). They can be be from 670 mm (26 in) to 750 mm (30 in) long, but the average length of an Olympic marmot is 710 mm (28 in). It is generally the largest marmot and is about 7% longer than the hoary marmot and Vancouver Island marmot. It shows the highest amount of sexual dimorphism of its species, with adult males weighing on average 9.3 kg (21 lb) and adult females weighing 7.1 kg (16 lb). Regardless of this, both sexes lose 50% of their body mass over the 7 to 8 months of hibernation in the winter. After this severe weight loss, the male marmots emerge from hibernation weighing about 4.1 kg (9.0 lb) and females weighing an average of 3.1 kg (6.8 lb). Covering their large bodies, marmots have two different layers of fur: soft thick underfur for warmth and coarser outer fur. As an infant, marmots’ fur starts off as being a dark gray color. Once it ages into a yearling, its fur becomes grayish brown with various lighter patches. When it reaches adulthood, the characteristics of its fur change again. Most of the year, its coat is brown on the body with smaller white areas, developing lighter brown patches during the summer. The marmot molts twice a year. The first time is in June, and it starts when two black patches of fur form on the back of the shoulders and spread to the rest of the body.^[5] In the fall, their fur is almost black, but after surfacing from hibernation in the spring they can be tan or even yellowish in color.^[6] The second molting is thought to occur during this hibernation, explaining the change in the color of the fur. This marmot’s muzzle is almost always white along with a white band in front of the eyes. It also has a long, bushy tail.^[7] Both its eyes and ears are small, along with short, stubby legs and sharp claws that aid them when digging their burrows.^[8]

A major difference between this marmot and the hoary marmot is that the hoary marmot has black feet and a black spot on its head, and overall is not as brown as the Olympic marmot, although they share almost every other physical trait.^[9] The Vancouver Island marmot is also similar to the Olympic marmot, but all of its fur is completely black.^[5]

Female Olympic marmots have a litter of between 3 to 6 in alternate years. The young do not reach sexual maturity until their third year, perhaps because of the short growing season. Estrus occurs about 2 weeks after Olympic marmots come out of hibernation, so about the middle to end of May; after hibernation ends, both male and female Olympic marmots attempt to entice the opposite sex. If a female has never produced a litter before, she tends to be more aggressive, and will instigate fights with males. Female Olympic marmots only breed with males once in two reproductive seasons. The relationship between a sexually mature male and female Olympic marmot is polygynous. About 4 weeks after mating, a female Olympic marmot gives birth to 3 to 6 babies weighing about 1.55 kg each in a grass-lined burrow underground. The pups cannot see, they have no fur, and they are pink in color when they are first born. It is about a month before the young Olympic marmots leave the burrow for the first time. Female Olympic marmots do not leave their young for more than 30 minutes at a time and stay close by until the offspring are ready to forage on their own, at several weeks of age.^[5][10]

Olympic marmots are gregarious burrowing animals. Their activity patterns differ depending on the weather, time of day, and time of year. Due to rainfall and fog cover during the summer months of June, July, and August, the marmots spend the majority of their day inside their burrows, and forage for food and interact with other marmots only in the morning and evening. They hibernate from September through May, but the rest of the year they are a diurnal species. Hibernation is the most dangerous time for the Olympic marmot because in years of light snowfall, as much as 50% of the young born in that year will die from the cold.^[11] Prior to hibernation, the marmots bring dry grasses into the burrow for bedding or food. In May, thick snow cover is still present from the 8 months of prior hibernation, so Olympic marmots aren't very active at this time.

A typical family of marmots, called a colony, consists of a male, two to three females, and their young. Newborns stay with their family for at least two years, so a burrow is often home to a newly born litter and a year old litter. These very sociable animals usually greet each other by touching noses or nose to cheek, but sometimes in more reproductive greetings, they'll also inter-lock teeth and nibble each others' ears and necks.^[5] They may also engage in play fighting, in which two marmots on their hind legs push each other with their paws. This play fighting is more aggressive between older marmots. When marmots feel threatened, they will voice one of a few different types of alarm calls. One type of alarm is the trill, which consists of multiple notes, and communicates to surrounding marmots that danger may be approaching and they should get back to their burrows. ^[12]

The Olympic marmot eats meadow flora species in the Olympic Peninsula, such as avalanche lilies, sub-alpine lupine, mountain buckwheat, harebells, and other grasses, flowers, and roots. This makes them a folivorous species. They obtain water through the vegetation they eat, including water in the plants and dew on the plants' surfaces. During the winter when snowfall covers this flora, these marmots resort to eating a more carnivorous diet. They become scavengers, picking up small, already dead animals such as Townsend's chipmunks. Since their usual source of water on plants is covered by snowfall, the snow begins to also serve as their water supply when it melts.^[5]

Olympic marmots, like all other marmots, have a variety of distinctive calls or whistles which alert other marmots to predators. There are four basic calls: ascending, descending, flat and trills. The first three calls are distinguished by relative frequency of their starting and ending pitch. The trills are a series of ascending calls in rapid succession and are the most rare, being reserved for situations of great danger. The flat calls are the most common. The calls can be heard here. Common predators of the Olympic marmot are the coyote and puma although the marmots have been observed making alarm calls for a number of large birds of prey as well as bears and bobcats.^{[citation needed]}

Olympic marmots are relatively easy to see on the very accessible Hurricane Ridge in Olympic National Park where they are quite numerous. Olympic marmots are in decline in some areas in the park. This is believed to be due to the encroachment of trees into the meadows as well as predation by coyotes. Olympic marmots are a protected species in Washington. In 2009, legislation was signed that declared the Olympic marmot to be Washington State's official endemic mammal.^{[citation needed]}