Donald Grayson of the University of Washington has found by studying archaeological sites that the pika has moved higher and higher in the mountains. His report is published in the current issue of the Journal of Biogeography.

Grayson blames climate change and human activity. He found that many former populations of pikas are extinct.

"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."

Grayson said that researchers from the University of California Berkeley Museum of Vertebrate Biology have made similar findings. They discovered that pikas were living at around 7,800 feet in the early 1900s but can now be found no lower than 9,500 feet in Yosemite.