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Meltdown in the Mountains: How Global Warming Threatens Pikas and Other High-Country Critters
Alarm Bells for the Alpine Zone
It’s high atop the world’s mountains, where it accounts for less than 5 percent of the Earth’s surface.
It’s battered by winds, it’s frigidly cold most of the year, and it is treeless.
Ecologists call it the alpine zone.
Most of the U.S. alpine acreage is in the West, where you find most of the nation’s high-mountain habitat. And this zone just may be zoning out. In recent years its average annual temperature has heated up, thanks to global warming, about 1 degree F. Computer models show the region going up an additional 4.5 to 14.4 degrees F during the next century.
As the alpine zone warms, scientists expect the snowpack up there to shrink, something that’s already been seen in the Pacific Northwest, the Southern Rockies and the Sierra Nevada. That snow loss means less moisture in the warmer alpine zones, with the result that alpine soils will dry out and evergreens and grasses from lower altitudes will move up mountainsides, crowding out native species.
Changes in alpine plant life already are happening. A paper published in the July 2005 Western North American Naturalist shows that Engelmann spruce have moved 575 to 650 feet upward in three of four areas studied in Nevada’s Great Basin National Park between 1992 and 2001.
Tell Me about Pikas and Global Warming
Okay. With round bodies, prominent ears, no visible tail and weighing just 5 ounces, the potato-sized pikas are the smallest members of the rabbit family. Frantic workers, they live high atop western mountains, collecting large piles of wildflowers and grasses during summer—a process called haying—to eat in winter.
Although pikas are among the toughest animals in the lower 48 states—spending their entire lives in alpine terrain—biologists fear that these unmercifully cute creatures may not survive global warming. Unlike many wildlife species that, in response to changing climate, are shifting their ranges north or to higher altitudes, pikas and other alpine animals have nowhere else to go.
In some locations entire pika populations already have disappeared. Scientists say the decline may be a warning about problems for other species, from butterflies and birds to large mammals.
Learn More About Pikas
- Pikas, which in the cold ice age lived across North America, have been retreating upward on mountains for the past 12,000 years.
- American pikas are found in Colorado, Oregon, Washington, Idaho, Montana, Wyoming, Nevada, California and New Mexico as well as western Canada. Their thick fur and round bodies conserve heat, and furry paws provide traction on snow. Though most pikas in the Lower 48 live only in alpine zones, some survive at lower altitudes where deep, cool caves are available, such as the ice tubes in California’s Lava Beds National Monument.
- Telltale signs of pika territory are the hay piles the animals build up in summer to eat during winter. The piles, which can each contain a bushel of plants, resemble dried flower arrangements.
- Like their rabbit relatives, pikas breed fast: Females can deliver two or three litters of as many as five pups per season, and the pups reach adult size in just three months—if a predator, usually a weasel, doesn’t eat them first.
- To protect their offspring, adults climb up to lookout rocks and emit distinctive “weasel calls” when they spot the little killers. Pikas also produce alarm calls for coyotes and for bird predators such as ravens.
- Initially, juveniles attempt to set up homes close to their parents but are soon chased away. Fiercely territorial, pikas squeak at invaders. “They will come out and yell at you if you get too close,” says Montana pika researcher Chris Ray.
Hello Heat, Goodbye Pikas
Trapped on mountaintops, alpine wildlife is easily damaged by several of global warming’s effects, including changes in plant life, invasion by new predators and pests, reduced winter snowpack and increases in extreme weather events. For pikas, one serious problem is heat itself. To survive in summer, they have to spend hot afternoons in cool, moist rock piles at the base of mountain slopes.
Researchers say that as temperatures rise, pikas will abandon lower-level slopes and migrate higher into the mountains until they can go no farther—much like living on the highest point of a sinking island. “All other mammal species in continental North America have greater heat tolerances,” says Colorado College alpine mammalogist Barry Rosenbaum, who is studying pikas on Colorado’s Niwot Ridge.
Haven’t Pikas Already Started Dying Off?
Yes they have. In the Great Basin—the dry region between the Rocky Mountains and California’s Sierra Nevada—pikas already are disappearing. According to National Park Service biologist Erik Beever, the little haymakers have recently vanished from 8 of 25 mountainous locations where they used to live in the early 1900s. Beever says the die-off happened because pika habitat is shrinking. Notably, the most-recent pika losses occurred at the warmer, southern end of the animals’ range. “This is what you would expect from rising temperatures—a loss at the margins of their distribution,” Beever says. The finding represents “one of the first contemporary examples of a North American mammal exhibiting a rapid shift in distribution due to climate.”
According to Chris Ray, who has studied pikas in rugged mountains near Bozeman, Montana, for 16 years, the animals also have disappeared from some rocky slopes in Montana’s Bridger Range during the past 30 to 40 years. While fossils show that pikas have been lost from several western mountain ranges over the past 10,000 years “the speed at which they are disappearing now is more rapid than ever before,” she says.
The content of this blog was adapted from a National Wildlife magazine story by Paul Tolmé, December/January 2006.