2012-02-21 "Yosemite's alpine chipmunk seeking cooler habitats" by David Perlman from "San Francisco Chronicle"
Backpacking scientists from UC Berkeley have gathered compelling evidence that the warming High Sierra climate is pushing still another animal species to seek cooler habitats amid the higher regions of Yosemite National Park.
Their new study, tracking changes in the home range of a single chipmunk species during the past 90 years, follows many other recent reports by field biologists that salamanders, field mice and ground squirrels, among others, also have been driven by rising temperatures to seek new homes at higher elevations in the park.
The new evidence for the effects of global warming comes from a study of the alpine chipmunk (Tamias alpinus) that Emily M. Rubidge, 36, a former UC Berkeley graduate student, carried out during four recent summers. Rubidge camped, hiked and surveyed the chipmunks among the talus slopes of Yosemite's higher mountains, where the animals live and rear their young.
Back in 1914, a famed Berkeley field biologist named Joseph Grinnell led a team of naturalists surveying the lives and habitats of virtually every animal living in Yosemite at that time. His tissue samples, plus 2,000 pages of notes, provided the details that Rubidge and her colleagues used to discover how much higher the chipmunk species has moved its home range.
Grinnell's time temperature records in the park also show that Yosemite has warmed by 5 degrees, she found.
Grinnell reported in 1914 that the lowest elevation in the park where he and his team could find the alpine chipmunks living was at about 7,800 feet. Today, Rubidge and her colleagues report that they have found none of the same chipmunk species living anywhere lower than 9,629 feet - a change in elevation of well more than 1,800 feet.
Back in the laboratory at UC Berkeley's Museum of Vertebrate Zoology - where Grinnell was the founding director long ago - Rubidge and her colleagues also discovered that the move toward higher elevations has significantly narrowed the genetic diversity of the animals since Grinnell's time. That development, a kind of "genetic erosion," has led many other species on a long downward slope toward eventual extinction.
To analyze those genes, Rubidge obtained cell samples from tiny ear clippings she took from 146 chipmunks that she trapped and released as she moved her campsites up toward 10,000 feet.
Her report on the changes in chipmunk habitat and in the animal's genes was published Sunday in a new refereed journal called Nature Climate Change. The study is part of a long-range UC Berkeley project documenting many changes in the animal life of Yosemite today compared with the Grinnell survey's reports of nearly a century ago.
Rubidge's team was led by UC evolutionary biologist Craig Moritz, who also leads the Grinnell Resurvey. Other co-authors of her report included James L. Patton, Marisa Lim and Justin S. Brashears of UC Berkeley and A. Cole Burton, who is Rubidge's husband and a wildlife ecologist at the Alberta Biodiversity Monitoring Institute in Canada, where Rubidge is now an independent consultant.