Olympic marmot

Appearance

The Olympic marmot's head is wide with small eyes and ears; the body is stocky with stubby legs and sharp, rounded claws that facilitate digging; the tail is bushy and ranges from 18 to 24 cm long. The Olympic marmot is about the size of a domestic cat; adults weigh from 3.1 to 11 kg and are from 67 to 75 cm in length, with the average being 71 cm . It is the largest marmot, about 7% longer than the hoary and Vancouver Island marmots. This species has the most pronounced sexual dimorphism found in marmots, with adult males weighing on average 9.3 kg and adult females weighing 7.1 kg .

The Olympic marmot has a double-layered coat consisting of soft thick underfur, for warmth, and coarser outer hairs. Infant marmots' fur is dark gray in color; this changes in the yearling period to grayish brown with lighter patches. The adult coat is brown on the body with some smaller white or pale brown patches for most of the year, becoming darker overall as the year progresses. The first molt of the year occurs in June, commencing with two black patches of fur forming on the back of the shoulders. This black coloration then spreads to the rest of the body, and by the fall the coat is almost black. A second molt is thought to occur during hibernation, and upon emergence from hibernation in the spring Olympic marmots may be tan or yellowish. The Olympic marmot's muzzle is almost always white, with a white band in front of the eyes.

The Olympic marmot can be readily distinguished from the hoary marmot, with which it shares almost every other physical trait, by the lack of contrasting black feet and a black spot on the head. The Vancouver Island marmot has a similar coat color, chocolate brown with white patches.

Distribution

Olympic marmots are native to the Olympic Mountains in the Olympic Peninsula of Washington state. About 90% of Olympic marmots' total habitat is located in Olympic National Park, where they are often sighted, especially on Hurricane Ridge. Marmots are in decline in some areas of the park due to the encroachment of trees into meadows as well as predation by coyotes, and they are seldom seen in the wetter southwestern part.

Within the park, Olympic marmots inhabit lush sub-alpine and alpine meadows, fields, and montane scree slopes. They live in colonies spread out in various locations in the mountains and containing the burrows of differing numbers of marmot families. Some meadows can contain as few animals as one marmot family, and some can have multiple families adding up to 40 marmots in total. There is a higher risk of inbreeding and death from random events in meadows with fewer marmots, making migration essential to the survival of the species. Burrows can be found at various elevations, ranging from 920 m to 1,990 m ; they are most often found in the range of 1,500 m to 1,750 m . Burrows are more frequently located on south-facing slopes, which generally receive more precipitation, 75 cm per year , and thus have more available flora. The home range of a family of marmots usually covers from half an acre to five acres . The Olympic marmot is well-adapted to its generally cold natural habitat, where there is snowfall almost every month of the year on the mountain slopes and barren grasslands.

Behavior

When greeting each other, these very sociable animals will usually touch noses or nose to cheek; in courtship rituals they may inter-lock teeth and nibble each other's ears and necks. 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. In fights that have been observed during a study, only about 10% of fights had distinct outcomes.

When communicating vocally, they have four different types of whistles, differing in this from their close relatives, the hoary marmot and the Vancouver Island marmot. The Olympic marmot's whistles include flat calls, ascending calls, descending calls, and trills; all of these are in a small frequency range of about 2,700 Hz. Flat, ascending, and descending calls are most often voiced singly. The ascending call has a duration of about half a second, starting with a "yell" on one note and ending with a "chip" on a higher note; it is often used as a distress or warning call for unfamiliar smells and noises. These same "yips" are heard when Olympic marmots are play fighting, along with low growls and chattering of teeth. The descending call ends on a lower note than it started on. The trill, which sounds like multiple ascending calls put together as one longer sound, consists of multiple ranging notes and is voiced as an alarm call to communicate to other marmots in the area that danger may be approaching and they should return to their burrows. Females with young have the responsibility to watch out for their young and other relatives near the burrow, and therefore voice the trill more often than other Olympic marmots. If marmots are not accustomed to human contact in a certain area, they may also sound a trill when seeing a person, in order to alert other marmots. At places like Hurricane Ridge, where seeing humans is a frequent occurrence, most marmots will not acknowledge human presence at all.

Olympic marmots also communicate through the sense of smell. A gland located in their cheek exudes chemicals which they rub on scenting points, such as shrubs and rocks, which can be smelt by other marmots in the area.The Olympic marmot, along with the hoary marmot, has the lowest reproductive rate of any rodent. A female Olympic marmot has a litter of from one to six young in alternate years. In a given year, a third of females will have a litter. Half of the pups die before the following spring. Those pups that survive the following spring can live into their teens. Both males and females mature sexually at three years, but females generally do not reproduce until they are four and a half years old. The marmot comes out from hibernation at the beginning of May, and estrus occurs about two weeks later. After hibernation ends, both male and female Olympic marmots attempt to entice the opposite sex with courtship rituals. Females who have never produced a litter before tend to be more aggressive and will chase or instigate fights with males; females which have already produced young tend to greet the male with nasal to nasal or nasal to genital contact, with copulation following shortly afterwards. This approach is more successful than the aggressive manner of the non-parous female, with mating taking place within 11 to 20 days after hibernation. The relationship between a sexually mature male and female Olympic marmot is polygynous; males tend to breed with three or four females in each mating season.

Approximately four weeks after mating, the female gives birth to her young in a grass-lined burrow underground. Newborn pups cannot see, have no fur, and are pink in color. At first, the young exhibit no sexual dimorphism. It is about a month before the young Olympic marmots first leave the burrow; around the same time, they begin to be weaned. Even after they are allowed to emerge, the young initially stay within the immediate vicinity of the burrow, where they can be found chasing each other and wrestling playfully. Within a few weeks after first emerging from the burrow, the young are fully weaned and can feed themselves. Olympic marmots are not completely independent from their mothers until they reach two years of age. Breeding-age female marmots are extremely important to marmot populations. If a female of breeding age dies it can take years to replace her; marmots are usually limited to six pups in a litter, the maturation period is long, and many marmots die before reaching maturity.

Habitat

Olympic marmots are native to the Olympic Mountains in the Olympic Peninsula of Washington state. About 90% of Olympic marmots' total habitat is located in Olympic National Park, where they are often sighted, especially on Hurricane Ridge. Marmots are in decline in some areas of the park due to the encroachment of trees into meadows as well as predation by coyotes, and they are seldom seen in the wetter southwestern part.

Within the park, Olympic marmots inhabit lush sub-alpine and alpine meadows, fields, and montane scree slopes. They live in colonies spread out in various locations in the mountains and containing the burrows of differing numbers of marmot families. Some meadows can contain as few animals as one marmot family, and some can have multiple families adding up to 40 marmots in total. There is a higher risk of inbreeding and death from random events in meadows with fewer marmots, making migration essential to the survival of the species. Burrows can be found at various elevations, ranging from 920 m to 1,990 m ; they are most often found in the range of 1,500 m to 1,750 m . Burrows are more frequently located on south-facing slopes, which generally receive more precipitation, 75 cm per year , and thus have more available flora. The home range of a family of marmots usually covers from half an acre to five acres . The Olympic marmot is well-adapted to its generally cold natural habitat, where there is snowfall almost every month of the year on the mountain slopes and barren grasslands.

Food

Olympic marmots eat meadow flora such as avalanche and glacier lilies, heather blossoms, sub-alpine lupine, mountain buckwheat, harebells, sedges, and mosses. They prefer green, tender, flowering plants over other sources of food, but roots are a large part of their diets in the early spring when other plants have not yet appeared. During May and June, they may resort to gnawing on trees for food. They also occasionally eat fruits and insects. Their water requirements are met from the juice in the vegetation they eat and dew on the plants' surfaces.

When snowfall covers vegetation, marmots have a more carnivorous diet, consuming carrion encountered while digging for roots and possibly killing late hibernating chipmunks. At this time, they also obtain water from melted snow. Hibernating Olympic marmots do not keep food in their burrows; instead, they gain fat before hibernating and can double their body weight to survive eight months without eating.