San Francisco State University
Department of Geography

Geography 316:  Biogeography

In progress 11/19/2001

The Biogeography of  Yellow-bellied Marmot (Marmota flaviventris)

by Stuart Smith,  student in Geography 316, Fall 2001

Kingdom:    Animalia Phylum:      Chordata Class:          Mammalia Order:         Rodentia Family:       Sciuridae Genus:        Marmota Species:      Marmota flaviventris
	Photo by Nick Nystrom

Description of Species:  Yellow-bellied marmots are rodents rather similar to squirrels, only bigger. Their closest relatives besides other marmots are the woodchucks that are so common in the eastern U.S. They are generally just shy of two feet long, varying in size from 45 to 57 centimeters long, with tails of 13 to 22 centimeters (Ballenger 1996). Males are generally heavier than females. Weights vary from two to five kilograms (Ballenger 1996). As their name implies, they generally have yellow or yellowish-brown straight fur on their undersides, with white tips. Lastly, the typical life span of these marmots is 13 to 15 years (Ballenger 1996).

Photo by Nick Nystrom

Habitat:  Yellow-bellied marmots usually occupy open territory, such as steppe, alpine meadows, pastures, or fields. They use rocky areas and talus for cover, and will usually build their burrows under the rocky part of their territory, if possible. This makes them much more difficult for their common predators to get at or dig out. They are found at altitudes of 2000 meters and up, with a wide range of suitable elevation. This is especially true in the Rockies, where it is common to find them at altitudes approaching 4000 meters or more (Barash 1989).

Photo by Mike Habeck

Yellow-bellied marmots build burrows that are more than one meter in depth, with several entrances. They choose the best drained soils in their territory in which to build. Burrows built for hibernation can be as much as five to seven meters deep. Burrow tunnels can be ten to seventy meters in length (Harris and Johnson 2001). For reproduction, they build grass nests inside the burrows. While they most often choose open grasslands, wet meadows, and fields in which to settle, they can also sometimes be found around the edge of stands of forest, especially subalpine conifer, as well as within open stands of lodgepole pines. They can be found additionally in the grassy understories of many types of forested areas, but these conditions are less ideal for them (Harris and Johnson 2001)

Photo by Michael Noonan

Natural History:
Eating habits
Yellow-bellied marmots eat the leaves and blossoms of many different plants and grasses. They also eat some fruits, legumes, grains, and even occasionally insects. In the late summer, they forage for seeds in preparation for winter hibernation. They confine themselves to food found on or near the ground (Stealey 1981).

Yellow-bellied marmots use the rocky areas near their burrows for both sunning and observation for predators (Stealey 1981). Their natural predators include badgers, coyotes, eagles, owls, and wolverines. They are a diurnal species, with food-gathering usually performed in two periods of activity: mid-morning and late afternoon. They hibernate from late September and early October until late April or early May, depending on climatic conditions and snowpack.

Reproductive Habits
They have a single breeding season each year, which begins shortly after they emerge from hibernation in the spring. The gestation period is roughly one month, so that most of the young are born in May and June. Litters can range in size up to nine pups (Stealey 1981). The average size, however, is three to five. For the first three weeks the young stay underground. After two weeks above ground, they are weaned. At the age of two, both males and females are sexually mature (Barash 1989). However, it is unlikely for yellow-bellied marmots to reproduce before the age of three, especially at higher elevations. Since survival through the winter depends on fat accumulation in the months prior to hibernation, the young stand a better chance of survival the sooner they wean from their mothers. It is common for females to reproduce only every other year at high elevations (Harris and Johnson 2001). These marmots are territorial, with each male having a harem of females with whom to mate. They are antagonistic towards other males. Male offspring are allowed to remain with their mothers until their second summer, and then are driven out. About half of the female offspring remain with their mothers permanently. Since the reign of a male over a harem and territory lasts only about three years before being replaced, inbreeding is not a problem, because the female offspring are not sexually mature until at least their second year, and very rarely reproduce before the age of three. As the family group of a single male becomes too large (typically over twenty), the group splits, and a solitary male takes over the new pack (Grzimek 1990). Marmots without a pack, both male and female, are highly susceptible to predation. Each male occupies a territory ranging in size from one half to five acres, with the average being about one and a half acres (Stealey 1981). Each harem consists of two to three females. The offspring are normally all raised jointly by the females of the harem. The males mark their territory with their scent (Van Gelder 1982). They do this by wiping a cheek scent gland over the rocky areas in their territory, and it has developed into a method for avoiding physical conflict with other males.

Evolution:

Yellow-bellied marmots can trace their ancestry back more than 25 million years, to the Oligocene epoch of the Cenozoic era. However, their forebears can be traced back much further than that, into the recesses of time more than 200 million years ago. Beginning more than 300 million years ago, during a time when the reptiles were the dominant form of animal, there began to evolve and differentiate a group known as the therapsid reptiles. These were the first reptiles to display mammal-like qualities, in the construction of their jaws and cranial features. They would evolve over 100 million years into the very first mammals. These little omnivorous mammals came into being during the age of the dinosaur, and were called Pantotheria. They were probably about the size of a mouse, and foraged at night, hiding in the day because of their oversize predators (Vaughan 1986).

By late in the cretaceous period of the Mesozoic era, the very first of these mammals had evolved into two distinct groups, marsupials (having a pouch) and placental mammals (having a uterus). This began a period of radiation, or intense development of new types, of placental mammals, which occurred during the Paleocene and Eocene epochs of the Cenozoic era, starting about 63 million years ago (Davis and Golley 1963). Indeed, the first rodents (the order of yellow-bellied marmots) evolved during the Paleocene epoch.

By the time the Eocene epoch had ended, so had radiation, and intensive specialization had begun, which produced the wide variety of mammals, and in particular rodents, that we see today. Some of the earliest rodents were of the primitive family Ischyromyidae, which gave rise during the Oligocene epoch to several rodent families, including the squirrels, or Sciuridae, of which yellow-bellies are a member. That happened as “recently” as 36 million years ago. These squirrels were present here in North America by the middle of this period, and by the end of this period, 25 million years ago, they had specialized and divided into two groups, the tree squirrels and the ground squirrels (yellow-bellied marmots are ground squirrels).

Thus began the separation of the various types of squirrels, right up through today. Marmots, or the genus marmota, separated from other types of squirrels during the Pliocene epoch, at the very end of the Tertiary period, beginning about 13 million years ago (Vaughan 1986).

Finally, in recent times beginning about two million years ago, marmots have begun to differentiate even more from the squirrel family in the reduction of their tail length (their tail is not essential in daily activities as it is for other squirrels), and increased forelimb strength.

Distribution

Yellow-bellied marmots are found in high rocky areas in many parts of the Sierra Nevada and Cascade mountain ranges, from Tulare County in California north to Oregon. In addition, they are found in parts of the White Mountains where they cross the border between California and Nevada. Finally, they also range in parts of the Rocky Mountains (Harris and Johnson 2001). While small populations can be found in the high desert hills of Nevada, they do not live below about 6000 feet in elevation, and do not thrive at the low end of their range of altitude, because they are better suited to higher-elevation living.

Map of Distribution:

Other interesting issues:

    Since the 1980's, a new habit of the yellow-bellied marmots in the Sierras has caught the attention of the national park staff at Sequoia and other parks. This is their penchant for eating the radiator hoses of unsuspecting backpackers, who often leave their cars for several days at remote trailheads in the parks. Rangers speculate that the marmots like the sweet taste of the antifreeze, or that they are attracted to the warmth of the undersides of the car engines. Either way, this has become more than just a nuisance. Needless to say, it is toxic for the marmots to consume the antifreeze, since it contains ethylene glycol. Additionally, there is a not-insignificant amount of inconvenience afforded to backpackers, who return from days on the trail only to find that their cars have to be towed many miles down backcountry roads! The more savvy among them now surround their cars with wire mesh before setting out, in an attempt to keep the marmots away from their cars. 
 

Bibliography 
Ballenger, Liz. (1996, January 18). Marmota flaviventris (yellow-bellied marmot) – Narrative. [Online]. Available: http://animaldiversity.ummz.umich.edu/accounts/marmota/m._flaviventris$narrative.html

Barash, David P. 1989. Marmots: Social Behavior and Ecology. Stanford, CA. Stanford University Press.

Grzimek, Berhnard. 1990. Grzimek’s Encyclopedia of Mammals. New York. McGraw-Hill.

Habeck, Mike. (2001). Eco-USA Fauna Profiles: Yellow-bellied Marmot. [Online]. Available: http://www.eco-usa.net/fauna/marmot.html.

Harris, J. and V. Johnson. (2001, July 24). California Wildlife Habitat Relationships System – M066 Yellow-bellied Marmot. [Online]. Available: http://www.dfg.ca.gov/whdab/cwhr/M066.html.

Noonan, Michael. (1999). Canisius Ambassadors for Conservation: Yellow-bellied Marmot. [Online]. Available: http://www2.canisius.edu/~noonan/cac1999/yellow-b.htm.

Nystrom, Nicholas A. (1999). Yellow-bellied Marmot. [Online]. Available: http://www.psc.edu/~nystrom/gallery/Yosemite1999/000399_c1.html.

Stealey, Victoria L. 1981. Behavior, Diet, and Ecology of the Yellow-bellied Marmot, Marmota Flaviventris, in the Sierra Nevada. San Francisco, CA. San Francisco State University.

Van Gelder, Richard G. 1982. Mammals of the National Parks. Baltimore, MD. Johns Hopkins University Press.

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