Saturday, December 31, 2005

ENV: Losing Pikas

American pika seen headed toward extinction

WASHINGTON (Reuters) -- Human activity and climate change may be pushing the tiny American pika toward extinction in the mountains of western North America, according to research published Thursday.

The small rabbit-like mammals live in rock-strewn slopes but are gradually being pushed to higher elevations and are running out of places to live, archeologist Donald Grayson reports in the current issue of the Journal of Biogeography.

"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," Grayson said.

Seven of 25 historically described populations of pikas in the Great Basin -- the area between the Sierra Nevada and Rocky Mountains -- appear to have become extinct by the end of the 20th century, Grayson said.

Among the intrusions that appear to imperil the pikas are roads built close to their habitat and pressure from grazing livestock, Grayson said.

He examined 57 archeological sites dating as far back as 40,000 years, as well as unpublished studies by other researchers, finding that the tiny mammals have been pushed higher over the years.

"The Great Basin pika is totally isolated on separated mountain ranges and there is no way one of these populations can get to another," Grayson said in a statement. "They don't have much up-slope habitat left."

Pikas, which are very sensitive to high temperatures, are considered to be one of the best early warning systems for detecting global warming in the western United States, the journal reported.