Yellow-bellied marmots are a small or medium-sized rodents. They have sturdy bodies with short, wide heads. Their bodies are covered in coarse hair that is lighter on the tips and darker at the base. This makes them look light brown overall. They have yellowish patches of hair on the sides of their neck, and white spots between their eyes. Their belly is yellow or orange-brown, which is how they get their name. Their feet are are tan, hazel, or dark brown. Different subspecies have different colors. Yellow-bellied marmots have small, furry ears. Their back feet have oval pads, and their claws are short and a little bit curved. Every summer, they lose all of their fur and then grow it all back. (Frase and Hoffmann, 1980)
Males are longer than females and quite a bit heavier. Males weigh 2.95 to 5.22 kg, and usually around 3.9 kg. Females weigh 1.59 to 3.57 kg, and usually about 2.8 kg. Yellow-bellied marmots are 470 to 700 mm long, and their tail alone is 130 to 220 mm long. Their back feet are 70 to 90 mm long, and their heads are 68.0 to 99.8 mm long. Yellow-bellied marmots living in low, dry places are often smaller than ones that live in mountains with more rainfall. (Frase and Hoffmann, 1980)
Yellow-bellied marmots live in many parts of the western United States and Canada. They are found as far north as southcentral British Columbia and Alberta in Canada, and as far south as the Sierra Nevada Mountains in California and Nevada. (Frase and Hoffmann, 1980)
Yellow-bellied marmots generally live in warm, dry areas. They are found in places that are almost deserts, open areas in forests, and in the mountains above where trees can grow. They are found on hills that also have plants or groups of rocks in meadows. Rocks support their burrows and give them spaces to sun themselves and be on lookout. They need burrows to raise their young, hibernate, and hide from predators, so they are found in places where there are good burrows. Yellow-bellied marmots that live farther south live higher up on the mountains. For example, in the White Mountains of California they only above 2000 m in elevation. This also means that farther south, they are live in disconnected groups. Across all places, they are usually found around 2,000 m in elevation. They don't live at very high elevation. Where there are hoary marmots, there are usually are not as many yellow-bellied marmots. (Blumstein, et al., 2006; Frase and Hoffmann, 1980)
Yellow-bellied marmots can live in colonies, in pairs, or alone. About 75% of them live in colonies, 16% in smaller groups, and 7% in temporary locations. Usually, males mate with more than one female. This happens a lot when they live in colonies, where males live together with multiple females and their young. They often move between different colonies, so about 40% of the yellow-bellied marmots in a colony came from a different one. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Yellow-bellied marmots have one breeding season per year right after they wake up from hibernating for the winter. The breeding season lasts about two weeks. The young grow inside their mother for about 30 days. Females have 3 to 8 pups, and 4.32 pups on average. Newborn pups are 111 mm long and weigh about 33.8 g. The young are able to breed when they are 2 years old, but only 25% of 2-year old females have pups. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Scientists don't know much about parental care in yellow-bellied marmots. Mothers feed their pups milk for about 3 weeks, and then the pups come out of the burrow. After the pups come out, parents don't spend as much time or effort caring for the young. However, the young are still bonded to their parents for a long time, especially when they are living in colonies. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Most yellow-bellied marmots live 13 to 15 years in the wild. They are impacted by predators, who cause 98% of their deaths in the summer. Other reasons they die are hibernation and traveling. In California, a lot of them recently died from sylvatic plague, which is caused by a bacteria. (Frase and Hoffmann, 1980)
Yellow-bellied marmots normally come out from their burrows in the early morning, and spend time grooming themselves and laying in the sun. By mid-morning, they look for food. Then, they lay in the sun more, groom themselves, and spend time in the burrow. By late afternoon, they eat again. Most of the time they're above ground, they lie in the sun with their head in an alert position. Because they hibernate for 8 months from September to May, they actually spend about 80% of their lives underground. They are 1 of only 2 species of marmots that don't hibernate in social groups. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Yellow-bellied marmots interact with each other in friendly and aggressive ways. Friendly behaviors are playing, grooming, and greeting each other. Grooming might show that the marmot who is grooming has higher social rank. Friendly behaviors usually happen between yellow-bellied marmots from the same burrow. Friendly behaviors happen more often when all of the marmots have lived together in the same burrow for more than 1 year. Aggressive behaviors are being alert, chasing, and fighting. Aggressive behaviors usually happen between yellow-bellied marmots from different burrows. Males are more protective of their territory in front of other males and adults. To protect their territory, they wave their tails back and forth or mark the ground with their scent. Both males and females will also act aggressively to their young to encourage them to leave the colony. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Scientists don't know the size of the area where yellow-bellied marmots usually live and travel.
Yellow-bellied marmots communicate with each other using noises and body language. The 3 most important noises they make are called: the whistle, the undulating scream, and the tooth chatter. There are 6 different whistles in total, that are used for alerting others about predators or threatening. Yellow-bellied marmots scream when excited or scared. They chatter their teeth as a threat. Other animals like American pikas and golden-mantled ground squirrels might respond to alarm calls of yellow-bellied marmots. If they are in a conflict, yellow-bellied marmots use their scents to communicate which one is more dominant. (Blumstein, et al., 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)
Yellow-bellied marmots eat only plants. They eat many kinds of plants like grasses, flowers, and other flowering plants. In late summer, they also eat a lot of seeds. They sometimes have trouble finding food in the spring, when the ground is still covered in snow. Yellow-bellied marmots don't eat the parts of plants that are toxic or poisonous. (Frase and Hoffmann, 1980)
Yellow-bellied marmots have many predators that live on land or fly. Their most important predator is coyotes, and then badgers, American martens, black bears, and golden eagles. Yellow-bellied marmots avoid predators by staying in underground burrows for a long time. This affects how they find food, their social behavior, and habitat selection. Marmots living in colonies are more likely to survive than the ones living at the edges of the habitat. (Armitage, 2004; Blumstein, et al., 2006; Van Vuren, 2001)
Yellow-bellied marmots compete with hoary marmots for food and space. Since yellow-bellied marmots eat seeds, they also affect the plants where they live. They are a good food source for many predators. Their burrows are used by other kinds of digging animals after they leave. (Nelson, 1980)
Yellow-bellied marmots carry the plague, which is caused by a kind of bacteria. In rare cases, humans that touch yellow-bellied marmots could get the plague, which is a deadly disease. (Nelson, 1980)
Yellow-bellied marmots are hunted for enjoyment, food, or fur in some places where they live. (Frase and Hoffmann, 1980)
There are 11 subspecies of yellow-bellied marmots. They are all closely related to hoary marmots. The two species overlap in a small part of northwestern Montana and western Washington. (Frase and Hoffmann, 1980)
Stefanie Hwang (author), The College of New Jersey, Matthew Wund (editor), The College of New Jersey, John Berini (editor), Animal Diversity Web Staff, Catherine Kent (editor), Special Projects.
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