Hoary Marmot (Marmota caligata) lives in alpine meadows across Northwestern North America. It feeds on grass and leaves. Its conservation status is Least Concern.
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Hoary marmots can grow as long as a small canoe, reaching 62-82 cm total length with a 17-25 cm tail, yet their bodies swell dramatically through the year, averaging just 3.75 kg in May and ballooning to about 7 kg by September. Most fall males tip the scales at 10 kg, but an extraordinary autumn male was recorded at nearly 13.5 kg, possibly the biggest marmot ever measured. Their size rivals that of the Olympic marmot and overlaps many Asian relatives, showing how alpine mammals can pack massive fat reserves for long winters.
When winter comes, hoary marmots retreat into a sprawling underground city they build themselves, hibernating for seven to eight months. Each colony keeps one deep hibernaculum plus a number of shallow refuge burrows, each 1-2 m deep, and digs about five new burrows a year, a mature colony can own over a hundred. The larger sleeping burrows and hibernacula stretch to roughly 3.5 m deep, offering insulated chambers lined with plant material. Because they spend about 80 % of their lives inside these tunnels, the burrow network helps with predator avoidance.
A hoary marmot colony is a tight-knit troupe of up to 36 individuals spread over about 14 ha (35 acres). One dominant male presides over up to three adult females, sometimes joined by a subordinate male, while yearlings and pups fill the rest of the roster. Social life buzzes with play-fighting, wrestling, grooming and nose-to-nose touching, especially as hibernation nears. Greeting rituals, nose-to-nose or nose-to-mouth contacts, are a greeting after emerging from burrows, individual recognition.
Reproduction in hoary marmots is a tightly timed sprint. After emerging from hibernation in May, mating begins and gestation lasts 25-30 days, so litters of two to five pups arrive between late May and mid-June. Females usually breed only every other year, producing an average of 3.3 offspring per successful litter. The newborns stay hidden in the den for three to four weeks, then are weaned by about four weeks, and only become sexually mature at about three years of age, ensuring the colony's continuity.
On clear July days they spend 44 % of their above-ground time basking on rocks. Sunning and looking up together make up the two most common above-ground activities, with about 30 % of daylight hours devoted to vigilance while they soak up heat.
Sources
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In the rugged expanse of alpine meadows, the hoary marmot reigns as a stalwart sentinel, its tawny coat glistening like burnished gold in the high-altitude sunlight. With a deliberate, unhurried gait, it moves through its kingdom, pausing periodically to survey its surroundings with a piercing, whistle-punctuated call that echoes across the mountainside. As it forages for the lush grasses and wildflowers that sustain it, the marmot's very presence seems a testament to the enduring power of life in this harsh, breathtakingly beautiful landscape.
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