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 (7.1 to 9.4 in) long.
The Olympic marmot is about the size of a domestic cat; adults typically weigh from 2.7 to 11 kg (6.0 to 24.3 lb) and are from 67 to 75 cm (26 to 30 in) in length, with the average being 71 cm (28 in).
This species may have the most pronounced sexual dimorphism found in marmots, with adult males weighing on average 4.1 to 9.3 kg (9.0 to 20.5 lb), post emergence in spring and at peak weights in autumn, respectively, and adult females weighing 3.1 to 7.1 kg (6.8 to 15.7 lb) at the same times.
Going on published weights, the Olympic marmot is the largest of the six marmot species found in North America, averaging slight heavier in mean body mass than hoary marmot and Vancouver marmot.
Mean linear dimensions suggest the Olympic species is about 7% larger on average than these other two large North America species.
Furthermore, it rivals some lesser-studied Asian species as the largest marmots and largest members of the squirrel family in general, with perhaps similar body masses attainable by some species such as the Tarbagan marmot and the Himalayan marmot.

The coat is double-layered, 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.

This species 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.
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 (7.1 to 9.4 in) long. The Olympic marmot is about the size of a domestic cat; adults typically weigh from 2.7 to 11 kg (6.0 to 24.3 lb) and are from 67 to 75 cm (26 to 30 in) in length, with the average being 71 cm (28 in). This species may have the most pronounced sexual dimorphism found in marmots, with adult males weighing on average 4.1 to 9.3 kg (9.0 to 20.5 lb), post emergence in spring and at peak weights in autumn, respectively, and adult females weighing 3.1 to 7.1 kg (6.8 to 15.7 lb) at the same times. Going on published weights, the Olympic marmot is the largest of the six marmot species found in North America, averaging slight heavier in mean body mass than hoary marmot and Vancouver marmot. Mean linear dimensions suggest the Olympic species is about 7% larger on average than these other two large North America species. Furthermore, it rivals some lesser-studied Asian species as the largest marmots and largest members of the squirrel family in general, with perhaps similar body masses attainable by some species such as the Tarbagan marmot and the Himalayan marmot.
The coat is double-layered, 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.
This species 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.
Olympic marmot