Inyo chipmunk's apparent disappearance indicates a changing Sierra

With button-brown eyes, striped cheeks and a bushy orange-black tail, the Inyo chipmunk has darted among the gnarled pines of the Sierra Nevada for centuries.

But it has apparently vanished.

"We have not been able to find it anywhere," said James Patton, a retired UC Berkeley professor of zoology who has scoured parts of the high Sierra over the past two years in search of the elusive species.

No one knows why – or when – the species vanished. There is talk about air pollution and competition from other chipmunk species. But most of the speculation centers on climate change, which has brought warming temperatures, earlier snowmelt and changing forest conditions to the region over the past century.

"Something is going on," said Patton, whose previous research helped show that the abundance and distribution of other chipmunks in the Sierra has changed, sometimes dramatically, as the range has warmed.

There is still a chance, of course, that some of the missing Inyo chipmunks may turn up somewhere. But Patton, one of North America's leading mammalogists, is not optimistic.

"As near as we can tell, it is gone from the Sierra," he said.

If true, it would mark the first time in many decades that a mammal has disappeared from the Sierra. And while Inyo chipmunks can still be found in the nearby White Mountains, their exit from the Sierra has struck a note of concern.

"Who knows where they are going to disappear next?" said David Graber, chief scientist for the Pacific West region of the National Park Service.

"The ecosystem of the Sierra Nevada is now more impoverished because it's lost this species."

While the Inyo chipmunk is the only one that has disappeared from the Sierra, other species of chipmunk are on the move.

The alpine chipmunk, for example, was common in Tuolumne Meadows at 8,600 feet above sea level in Yosemite National Park a century ago. Today, it can be found only at higher, cooler elevations. Another species abundant in Yosemite in the early 1900s, the shadow chipmunk, is now exceedingly rare.

All of which makes Patton believe chipmunks (left: shadow chipmunk) are the most sensitive barometers of climate change in the Sierra – more so than the rabbit-like pica, which live above the tree line and have become a poster child for global warming and a magnet for research dollars.

"Pica are easy to study," said Patton. "Anybody can go out and determine whether they are present. It takes an expert, for the most part, to distinguish species of chipmunks in the field.

"Chipmunks are giving us a bigger signal of change than any of the other small mammals in the Sierra Nevada," said Patton. "Chipmunks are far more interesting than what everybody is focusing on."

Could a few degrees, though, make a difference to a chipmunk?

"They don't look like the kind of animal that would have a direct temperature issue," said Graber, the Park Service scientist.

"That makes me believe this is a food issue, that their habitat has changed and they don't have what they need to make a living," Graber said. "Of course, that's speculation. I don't really know."

Not much is known about the Inyo chipmunk (left) itself. Guidebooks show the animal, a subspecies of the more widely distributed Uintah chipmunk, is 4 to 5 inches long, weighs just 2 to 3 ounces and was found only at higher elevations in the southern Sierra.

Patton began searching for the species in the Cottonwood Lakes Basin west of Lone Pine at 11,200 feet above sea level in 2009, setting out hundreds of small live traps, baiting them with rolled oats and comparing his results with those of pioneering zoologist Joseph Grinnell, who collected specimens in the same area in 1911.

Back then, Grinnell found alpine chipmunks were abundant among the wind-stunted pines of the basin. Inyo chipmunks were fairly common. And another species, the lodgepole chipmunk, was rare.

Last summer, Patton found that much had changed. Lodgepole chipmunks (left) were everywhere. Alpine chipmunks were scarce and living in the rocks above tree line. And the Inyo was gone.

In August, he returned again, hoping against hope to find an Inyo chipmunk. But not a single one turned up.

"We just have not been able to find them at any of the historic localities," said Patton, who is the curator of mammals at the University of California, Berkeley, Museum of Vertebrate Zoology. "It's what we would call an extirpation from the Sierra Nevada, for reasons unknown."

If his assessment is correct, the roster of Sierra Nevada chipmunk species will drop from nine to eight.

Source:
Sacramento Bee, "Inyo chipmunk's apparent disappearance indicates a changing Sierra", accessed October 8, 2010
McClatchy, "Inyo chipmunks disappear from Sierra Nevadas", accessed October 8, 2010