Longtime pika scientist Erik Beever reports that of 25 well-documented sites he has studied in the Great Basin (the area between the Rockies and the California-Oregon ranges) he now finds eight of them empty.
"The pikas are completely gone from a third of their sites, " Beever told us. "It's clearly related to global warming," he said, because thermal influences appear to be the most important driver of pika losses. However, Beever also said it is also clear that those temperature influences are combining with other factors-- such as the extent of rocky habitat and land use factors such as roads-- to affect populations across the Basin.
"Pikas are poor dispersers -- they can't just race over and recolonize an old site from another mountain," Beever explained.
"It's almost always too hot down in the valleys they'd have to cross," he said. "They'd run into uncrossable highways that weren't there when the last ice age ended. And they'd have to be out in the open, so they'd be in great danger of getting picked off by hawks."
So, with temperatures rising, the only way pikas have to go is up, chased by the steadily climbing warmer air that climate change is bringing -- and will continue to bring -- for at least the next 50 years, scientists say.
And when that heat reaches the top of a peak, that mountain's pikas are finished.
"Falling off the tops of mountains," as field biologists put it.
Hundreds of studies report a growing number of species of plants and animals migrating further up slope, looking for cooler ground and, when there's no more to go, disappearing altogether.
In one extensive study of the California Sierra Nevada Mountains, researchers found many species have moved more than 2,000 feet up slope from traditional sites.
Studies are finding that global warming, as it scatters local ecosystems that evolved over eons, has countless ways to attack them -- not only the direct overheating effect of the rising temperatures.
Mountain frogs, for example, have been shown to be dying from a fungus that is made more lethal by warmer weather.
Ray said that in addition to the loss of winter snow cover and the risk of overheating in summer, she and her colleagues are also now considering whether a plague infection, already found in other animals and possibly spreading due to climate change, may also be attacking some pikas.
"Local pika extinctions are accelerating," said Ray.
With temperatures only expected to rise, the American pika is now looking out on a fast-changing world, and facing a problem bigger than weasels.