New research indicates the small mammals, which are very sensitive to high temperatures, are being pushed upward in their mountain habitat and are running out of places to live. Climate change and human activities appear to be primary factors imperiling the pika, reports University of Washington archaeologist Donald Grayson in the current issue of the Journal of Biogeography.
Grayson's research which looks at a 40,000-year record of archaeological and paleontological sites, combined with yet unpublished work by several other researchers, paints a bleak future for the American pika (Ochotona princeps) in the Great Basin.
"Human influences have combined with factors such as climate change operating over longer time scales to produce the diminished distribution of pikas in the Great Basin today. This makes controlling our current impacts on them all that more important," said Grayson.
Human activities that appear to impact the animals include the proximity of roads to their habitat and pressure from grazing livestock.
The animals are isolated in patches across mountainous areas in western North America, from the southern Sierra Nevada and Rocky mountains to central British Columbia in Canada. In the Great Basin, these mountains are separated by large valleys with desert-like conditions that pikas can't tolerate. Pikas live in rock-strewn talus slopes that provide them with air-conditioning from hot temperatures and protection from predators.
Grayson's analysis of 57 well-dated archaeological sites, dating as far back as 40,000 years, shows that pikas have been pushed to higher and higher elevations. During the late Pleistocene and early Holocene epochs, 40,000 to about 7,500 years ago, now-extinct populations of Great Basin pikas were found at an average elevation of l,750 meters (5741 feet). The average minimum elevation of 18 surviving Great Basin populations surveyed in 2003 by Erik Beever, now with the National Park Service, was 2,533 meters (8,310 feet). These populations are scattered across Nevada, eastern California and southern Oregon.
Seven of the 25 historically described populations of Great Basin pikas also appear to have become extinct by the end of the 20th century. Grayson said the bad news has continued with new findings, as yet unpublished, by Beever and by James Patton, of the University of California Berkeley Museum of Vertebrate Biology.
Beever recently discovered two more pika population extinctions in the Great Basin and another increase of 132 meters (433 feet) in the lower elevation range of the animals at the locations where populations still remain. Patton, who has been studying wildlife in Yosemite National Park, which is in the Sierra Nevada Mountains adjacent to the Great Basin, has reported a 1,700-foot upward increase in the range of pikas there over the past 90 years. Found as low as 7,800 feet in the first decade of the 20th century, the animals now can't be found below 9,500 feet in Yosemite.
"We might be staring pika extinction in the Great Basin, maybe in Yosemite, too, right in the face. Today, the Great Basin pika is totally isolated on separated mountain ranges and there is no way one of these populations can get to another," said Grayson. "They don't have much up-slope habitat left."
"Pikas are an iconic animal to people who like high elevations. They are part of the experience. What's happening to them is telling us something about the dramatic changes in climate happening in the Great Basin. Climate change will have a dramatic effect including important economic impacts, such as diminished water resources, on people."