is native to the Olympic Peninsula. The species now is classified with all other marmots in the genus Marmota. Zoologist R. L. Rausch classified the Olympic marmot as the subspecies olympus of Marmota marmota (he included all North American marmots in this species, which now only includes the Eurasian Alpine marmot) in 1953, but it has usually been treated as a distinct species, a classification supported by taxonomic reviews starting with that of zoologist Robert S. Hoffmann and colleagues in 1979. Within Marmota, the Olympic marmot is grouped with species such as the hoary marmot (M. caligata) in the subgenus Petromarmota. Among this grouping, mitochondrial DNA analyses suggest that the Olympic marmot could be the most basal species. The Olympic marmot is thought to have originated during the last glacial period as an isolated relict population of the hoary marmot in the Pleistocene ice-free refugia. As of October 2011, molecular data based upon the taxonomy of the Olympic Marmot was able to approximate the initial immigration of the species from Russia to their current location of the state of Washington, also known as the trans-Beringian exchange. Contrary to initial thought, this species of Marmot is thought to have crossed the Bering Strait 4.6 million years ago. The Olympic marmot deviates from the typical Petromarmota marmots in the shape and large size of its mandible (jawbone), in differences of the dorsal (back) region, and having 40 chromosomes instead of 42, all of which are characteristics that resemble the subgenus Marmota. Some of the differences of the Olympic marmot's jawbone from the typical Petramarmota are also evident in the Vancouver Island marmot (M. vancouverensis), which evolved separately, but also occurs in a restricted range with a small population. Description 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 long. The Olympic marmot is about the size of a domestic cat; adults typically weigh from and are from in length, with the average being . This species may have the most pronounced sexual dimorphism found in marmots, with adult males weighing on average , post emergence in spring and at peak weights in autumn, respectively, and adult females weighing at the same times. Going on published weights, the Olympic marmot is the largest of the six marmot species found in