A Marmot's Life – The yellow-bellied marmots

Marmots come out of hibernation in April and early May, often when the landscape is still covered in snow and very little food is available. This is also a particularly dangerous period for them because predators are waiting for opportunities to catch the newly emerged animals. Foxes and coyotes have been observed waiting near the entrances of snow tunnels leading from marmot hibernacula, ready to capture marmots as they emerge.

Despite these risks, this period coincides with the marmots’ mating season. Males may travel between different hibernacula as they search for and visit females within their harems. In some remarkable cases, males have even been observed carrying dried flowers to females they may be courting.

Feeding and Growing After the Snow Melts

Once the snow disappears and vegetation becomes available, marmots begin feeding extensively. As herbivores, they consume a wide range of grasses and forbs. Eating enough food is essential because marmots need to increase their body mass substantially during the active season. They must roughly double their weight over the course of the year to build sufficient reserves for surviving the following winter.

Marmot pregnancy lasts approximately 32 days. After giving birth, females remain with their young in the natal burrow and nurse them for roughly another month before the pups are ready to emerge above ground.

Marmot Pups and Litter Size

Young marmots typically first appear above ground from late June through late July. Once they emerge, they must increase their body mass by more than two times to give themselves a strong chance of surviving the remainder of the year.

A typical litter contains around 3–4 pups, although considerable variation occurs. Litters observed in the population have ranged from just 1 pup to as many as 9. This wide difference in litter size makes the population particularly valuable for studying how the number of offspring influences reproduction and overall fitness.

Surviving Predators

Young marmots face especially high risks from predators after leaving their burrows. Resident red foxes have been known to kill every pup in the town area and most of the pups living within the neighboring 2 km. Other predators include coyotes, birds of prey, and bears.

To survive these threats, marmots rely on a complex collection of anti-predator behaviors. They devote part of their time to watching for danger and adjust how much vigilance they use depending on the level of risk associated with a particular location.

Marmots can recognize predators through several senses, including sight, hearing, and smell. Their ability to escape quickly has also been shaped by natural selection, and they can run at approximately 3 meters per second when fleeing danger.

When a predator is spotted, marmots use alarm calls to warn other members of their group. These vocalizations can communicate information about the seriousness of the threat. Marmots also carefully choose the areas where they feed, balancing access to food with the potential danger from predators.

Hibernation and Stored Energy

Marmots that successfully make it through the summer begin hibernating in late September. During this long dormant period, they depend entirely on the fat reserves accumulated during the warmer months.

Research on captive marmots has provided insight into the energetic demands of hibernation. The process consists of repeated periods of deep torpor followed by brief arousals. During deep torpor, a marmot’s body temperature falls to only a few degrees above the temperature of its surrounding burrow. During periodic arousals, the animal wakes, urinates, and then returns to another prolonged period of torpor.

In the coldest part of winter, these deep-torpor periods can last for approximately two weeks. As spring approaches, the torpor periods become shorter and the marmots maintain warmer body temperatures.

Hibernation is remarkably economical during the depths of winter, when marmots use very little energy. Spring, however, is much more demanding. Animals that emerge early and encounter little or no available food can lose a substantial amount of body mass, making the timing of emergence an important factor in their survival.