Neighbors on the tundra
July 17, 2013
EAGLE COUNTY — Marmots and pikas are neighbors in the rocks on the alpine tundra, but their morphology, appearance and survival strategies are dramatically different.
Yellow-bellied marmots (Marmota flaviventris) are often identified as woodchucks or groundhogs. They are related to those rodents and are the largest ground squirrel in Colorado. The name is possibly post-classical Latin, mus montanus, meaning "mountain mouse." In Colorado they are often called whistle pigs because of their loud shrill whistle.
There are 15 species of marmot, but there are only four that are found in North America. The hoary marmot is found in much of northwestern North America, the yellow-bellied marmot makes its home in southwestern Canada and western United States, the Olympic marmot can be found on the the Olympic Peninsula and the Vancouver Island marmot on Vancouver Island.
Marmots are heavy looking squirrels that can weigh as much as 11 pounds and can be over 25 inches in length. Their brown fur has grizzled tips, and they are darker around the head. The belly is yellowish, hence the name.
Marmots live mostly in higher mountain areas where they create burrows, usually in large rock piles. They are often found in rock piles in montane forests and are occasionally found in the foothills. On the tundra they survive on roots, grasses, sedges, flowers, mosses and lichens. Many times you will see them flattened out on a rock, soaking in the sun.
Raptors, coyotes and other carnivores found in the mountains are their predators. They have a social system that provides some protection from predators. When a whistle pig spies a predator they let out a shrill whistle, and all the marmots in the area take cover.
Marmots usually breed in April and their litter is typically two to five offspring each year. A dominant female will claim a territory and then create a burrow system with a male where they live with their offspring from previous years. Young males leave the group after their first or second winter. The females tend to hang around and may inherit their mother's breeding territory. Marmots may live as many as 14 years.
Pikas (Ochotona princeps) are dramatically different. They are found in the same high mountain environments, but do not range much below the tundra. They are small, under 8 inches in length and weigh less than 12 ounces. They have short legs, rounded ears and no visible tail. Many who see them think they are some kind of mouse, but in reality this animal is in the lagomorph family, which includes rabbits and hares.
Like the marmots, they also feed on roots, grasses, sedges, flowers, mosses and lichens.
The pika has many aliases, including whistling hare, cony and rock rabbit. Pikas have the same predators as marmots and also have a high-pitched alarm call when they spy prey and dive into their rock burrows.
Pikas breed in March or April. The litter is born after about 30 days and may consist of three or four young. The life span is four to seven years.
Even though they both live in the same environment there is a big difference in how they survive the winter. Marmots sleep through it and pikas continue to be active.
During the summer, marmots eat like crazy and put on a large amount of weight. When winter approaches they dig a deep burrow and line it with vegetation. Marmots are true hibernators. Hibernation is a process where their body slows down. The heart rate drops to as few as five beats per minute, respiration is one to two beats per minute, and the body temperature drops as low as 40 degrees. If the temperature around them approaches the freezing point, their heart rate and respirations will speed up. During hibernation they may lose 40 percent of their body mass. If they fail to put on a large layer of fat, or dig a deep enough burrow, they may starve or freeze to death before summer comes around. Any effort to rouse them during the winter would take some time because they need to warm up.
Pikas use an all together different strategy. They are active year-round. During the summer they harvest the alpine vegetation and pile it under boulders. These hay piles can be as much as a bushel in size. During the winter they dive in and eat themselves out of house and home. When one hay pile is used up, they move to another. They are often seen on windswept rocks during the winter months. If they fail to store enough food, they may not survive the winter.
Two unique critters that live in the same environment, eat the same foods, but survive the winter in dramatically different ways.
Rick Spitzer is the author of "Colorado Mountain Passes," published by Westcliffe Publishers and available at The Bookworm of Edwards, City Market, Amazon and many stores across the state. The book provides photos and text about the history, lore, wildlife and scenery around the passes of Colorado.