Marmota flaviventris
yellow-bellied marmot

Yellow-bellied marmots are distributed widely in the western United States and Canada. They range as far north as southcentral British Columbia and Alberta in Canada and as far south as the Sierra Nevada. (Frase and Hoffmann, 1980)

Yellow-bellied marmots generally live in moderately warm, dry habitats at low to mid elevations. They are found in many different habitats, including semi-desert, woodland and forest openings, and the alpine zone. Those that live further south live at higher elevations. For example, in the White Mountains of California they are found only above 2000 m. Moreover, because of absence from valleys, southern populations are isolated from one other, forming isolated populations. In addition, congeners may affect their distribution. It can be inferred that the presence of hoary marmots inhibit the distribution of yellow-bellied marmots in certain high elevation areas, as both occupy subalpine and alpine areas. Yellow-bellied marmots inhabit vegetated fortified slopes or rock outcrops in meadows, which serve as support for the burrows that they reside in, as well as sunning and observation posts. The main entrance of burrow, which they dig themselves, is usually about 0.6 m deep into the ground, and extends about 3.8 to 4.4 m horizontally into the hillside. Many short tunnels branch from main passageway, sometimes connecting to other burrows. Burrows stay relatively stable and thus serve as preferable places to raise young, hibernate, and hide from potential predators. Burrow availability may affect marmot distribution, as well as visibility and safety from predators. Most yellow-bellied marmots occur around 2000 m in elevation. (Blumstein, Ozgu, and Yovovich, 2006; Frase and Hoffmann, 1980)

Yellow-bellied marmots are a small to medium-sized rodents. Males weigh from 2.95 to 5.22 kg, with an average of 3.9 kg. Females range in mass from 1.59 to 3.57 kg, with an average of 2.8 kg. Total length ranges from 470 to 700 mm, with tail length ranging from 130 to 220 mm. Hind-foot length from 70 to 90 mm, and condylobasal length ranges from 68.0 to 99.8 mm. Males are longer than females and weigh significantly more. Also, individuals from low, arid-land habitats tend to be smaller than those from mesic, montane habitats. They have robust bodies, with short and broad heads. The head has a narrow interorbital region, with temporal ridges brought joining to form a low, short, sagittal crest. The posterior end of the palate lies obtusely, and the teeth of the upper jaw lie slightly more anterior than the teeth of the bottom jaw. The dental formula is 1/1, 0/0, 2/1, 3/3 = 22. The cheek teeth are high-crowned. Yellow-bellied marmots have small, well-furred ears, feet with five digits and an oval pad in the center of the sole of the hind foot, short and slightly curved claws with a rudimentary nail-bearing thumb, and ten mammae – two pectoral, two abdominal, and one inguinal pair. (Frase and Hoffmann, 1980)

The underfur of yellow-bellied marmots is soft, dense, and wooly on the back and sides of the body. Longer, coarse outer guard hairs with lighter tips and darker bases cover the entire body, making the overall color yellow-brown to tawny. Individuals are rarely dark brown and never black, except in melanistic individuals (common in populations in southern Rocky Mountains). There are also noticeable buffy yellowish patches on the side of the neck, white spots between the eyes, and a yellow or orange-russet color covering the belly, with feet a buffy, hazel, or dark brown color. There is great variety in color within subspecies. Yellow-belied marmots molt once annually during summer. (Frase and Hoffmann, 1980)

Most yellow-bellied marmots live for 13 to 15 years in the wild. Predation, which accounts for 98% of summer mortality significantly limits the average lifespan of this species. A significant number of deaths occur during hibernation and emigration. Recently, sylvatic plague, caused by the bacterium Yersinia pestis, has had a significant impact on populations in California. (Frase and Hoffmann, 1980)

Yellow-bellied marmots normally appear from burrows soon after sunrise, defecate, and spend time grooming and sunning. They forage by mid-morning, followed by sunning, grooming, and long intervals in the burrow. They feed again by late afternoon. Most time spent above-ground involves sunning with head in an alert position. Social interactions that have been observed are either amicable or agonistic. Amicable behavior includes play, grooming, and greeting behavior. Play occurs often between young, young and adults, and between yearlings, and may help individuals to socially integrate. Furthermore, grooming may suggest a dominant-subordinate role. Agonistic behavior includes grooming, social mounting, alert behavior, chasing, and fighting. Interactions between those of the same burrow are amicable, while agonistic interactions happen in those of different burrows. Rates of amicable behavior are also related to length of time the individuals live together - amicable behavior increases when all individuals have lived in the same burrow for longer than a year. In addition, territorial males are more hostile towards male yearlings and adults. Territorial behavior includes tail flagging, and marking habitat with anal glands. All males and most females leave the colony one year after birth. Female aggressive behavior towards litters is partly responsible for dispersal. Agonistic behavior by the male affects the leaving of male yearlings, but is not the primary cause of dispersal. Dispersal of yearlings may be delayed if there are a lot of yearlings, if they are underweight, and if there are high levels of amicable behavior between yearlings and adults. (Blumstein, Im, and Nicodemus, 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)

Yellow-bellied marmots spend about 80% of their lives in burrows due to winter hibernation. Hibernation lasts about eight months and occurs from early September to May, but may vary from year to year. Of the time spent underground, 60% is allocated to hibernation. Young marmots lose 50% of their body weight hibernating, thus reaching the threshold weight is important by fall. Hibernation is a cause of great mortality rates of all age groups of yellow-bellied marmots. Of the 14 species of g. Marmota, only two (Marmota monax and M. flaviventris), are not social hibernators. Only the young of M. flaviventris have been reported to hibernate socially. (Blumstein, Im, and Nicodemus, 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)

Home Range

There is no information available regarding the average home range of yellow-bellied marmots.

Communication between yellow-bellied marmots is mostly auditory and visual. There are three main vocalizations: the whistle, the undulating scream, and the tooth chatter. Six different whistles are recognized and may have more than one function, such as alerting and threatening. Screams usually respond to excitement or fear, and tooth chattering is used as a threat. Other animals such as American pikas and golden-mantled ground squirrels may respond to marmot alarm calls. Yellow-bellied marmots have cheek and anal glands. Scent marking occurs with cheek glands in conflict situations, having more of a dominance rather than territoriality function. (Blumstein, Im, and Nicodemus, 2004; Frase and Hoffmann, 1980; Wey and Blumstein, 2010)

Yellow-bellied marmots are herbivorous, eating a large range of plant types, including grasses, flowers, and forbs. In late summer, large numbers of seeds are eaten. They are most likely not food limited, eating only 0.8 to 3.1% of available net primary production. Food might be limited in areas where snow cover remains into the spring. They are selective feeders and are known to reject parts of plants that are toxic. (Frase and Hoffmann, 1980)

Yellow-bellied marmots have a variety of aerial and terrestrial predators. Coyotes are their most important predator, followed by badgers, American martens, black bears, and golden eagles. Risk of predation may influence foraging behavior, social behavior, and habitat selection, as individuals attempt to reduce risk of predation by remaining in borrows for extended periods of time. Predation appears to be only a minor cause of mortality for colonial animals and is more significant among populations residing at habitat margins. (Armitage, 2004; Blumstein, Ozgu, and Yovovich, 2006; Van Vuren, 2001)

Interspecific competition with other species, such as hoary marmots may affect the distribution and density of yellow-bellied marmots. As seed predators, yellow-bellied marmots may serve as habitat engineers that contribute to the density and composition of plant communities throughout their geographic range. In addition, yellow-bellied marmots are important prey for a number of different aerial and terrestrial predators. Once abandoned, burrows likely serve as important habitat for other fossorial and semi-fossorial species. (Nelson, 1980)

Yellow-bellied marmots are known carriers of the plague, caused by the bacterium Y. pestis. Although uncommon, humans that come into direct physical contact with this species may be at risk of contracting the plague. (Nelson, 1980)

In certain regions of its geographic range, Marmota flaviventris is killed for sport, food, or fur. (Frase and Hoffmann, 1980)

Yellow-bellied marmots are classified as a species of "least concern" on the IUCN's Red List of Threatened Species. Currently, there are no major threats to the long-term persistence of this species. (Armitage, 2004; Blumstein, Ozgu, and Yovovich, 2006; Van Vuren, 2001)

There are 11 recognized subspecies of yellow-bellied marmot. These include Marmota flaviventris avara, M. f. dacota, M. f. engelhardti, M. f. flaviventris, M. f. fortirostris, M. f. luteola, M. f. nosophora, M. f. notioros, M. f. obscura, M. f. parvula, and M. f. sierrae. Yellow-bellied marmots are closely related to hoary marmots. The two species overlap in a small range in northwestern Montana and western Washington. Significantly high genetic variation between colonies is a result of moderately low gene flow from colony to colony coupled with genetic drift. Despite great genetic variation, gene flow is adequate enough to circulate genetic variants between colonies. This is due to the dispersal of many young yellow-bellied marmots from their birth colonies. (Frase and Hoffmann, 1980)