It is the largest North American ground squirrel and is often nicknamed "the whistler" for its high-pitched warning issued to alert other members of the colony to possible danger.

Whistler, British Columbia, originally London Mountain because of its heavy fogs and rain, was renamed after these animals to help make it more marketable as a resort.

[6] The hoary marmot predominantly inhabits mountainous alpine environments to 2,500 metres (8,200 ft) elevation, although coastal population also occur at or near sea level in British Columbia and Alaska.

[6] Hoary marmots occur from southern Washington and central Idaho north, and are found through much of Alaska south of the Yukon River.

[14][6] They live above the tree line, at elevations from sea level to 2,500 metres (8,200 ft), depending on latitude, in rocky terrain or alpine meadows dominated by grasses, sedges, herbs, and Krummholz forest patches.

Predators include golden eagles, grizzly and black bears, wolverines, coyotes, red foxes, lynxes, wolves, and cougars.

Sleeping burrows and hibernacula are larger and more complex, with multiple entrances, deep chambers lined with plant material, and stretching to a depth of about 3.5 metres (11 ft).

Hoary marmots are also vocal animals, with at least seven distinct types of calls, including chirps, whistles, growls, and whining sounds.

[6] Hoary marmots frequently sun themselves on rocks, spending as much as 44% of their time in the morning doing so, although they will shelter in their burrows or otherwise seek shade in especially warm weather.

Hoary marmots breed shortly after,[18] or even before,[19] their emergence from hibernation burrows in May and in some areas (such as the eastern Cascade foothills of Washington State)[citation needed] as early as February.

[20] The young are initially cautious, but begin to exhibit the full range of nonreproductive adult behavior within about four weeks of emerging from the burrow.