Scientists blame climate change for loss of pikas in Lake Tahoe | SierraSun.com

Scientists blame climate change for loss of pikas in Lake Tahoe

Claire Cudahy
ccudahy@tahoedailytribune.com

A furry mountain rodent, known as the American pika, has disappeared from a large stretch of habitat in North Lake Tahoe, the largest pika die-off in the modern age, according to UC Santa Cruz scientists.

A study published in PLOS One in August outlines the findings of a six-year, and ultimately unsuccessful, search for the high-elevation rodents in a 165-square-mile area of the Sierra Nevada. Lake Tahoe, the Truckee River and Californai Highway 267 bound this roughly triangular zone surrounding Mount Pluto.

The research team, led by biologist Joseph Stewart, began monitoring the area when the pika was petitioned for listing under the California and federal endangered species acts.

"When we found old pika poop in every talus field that we looked at along the Truckee River, which is super low elevation, we started scratching our heads. If there is old pika poop here, where did the pikas go? Are they at higher elevations?" Stewart said. "The next six years we surveyed at progressively higher and higher elevations until we realized that, oh my god, pikas are extinct from this whole huge area."

The pika is a hamster-sized relative of the rabbit, which has adapted to surviving in cold, snowy winters. During the summer months they move between rocky fields and meadows, stocking their dens with grass and other plants.

"There are thermal physiological studies that show their upper critical limit is only 3 degrees celsius above their resting body temperature. So, they are very well adapted to surviving under the snow in the wintertime. Unlike otaher species at high elevations, like marmots and other species that live in their environment, pikas don't hibernate," Stewart explained.

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Instead, the pika has a thick coat of fur covering its whole body and a high metabolic rate that acts as a furnace.

"The same adaptations that allow them to stay warm over the winter time make them vulnerable to overheating," said Stewart.

Stewart believes the pikas either died of hyperthermia from foraging in too hot of conditions, or did not collect enough food due to the warmer temperatures and ended up starving or not reproducing.

It's difficult to estimate how big of a blow this is to the pika population in California, but Stewart said the loss echoes what occurred after the last ice age, only this time the change in climate is unfolding in a matter of decades versus millennia.

"It's indicative of a very worrying trend. If we don't reign in global warming pollution, about a million species or 15 percent of species on earth are vulnerable to extinction from climate change," said Stewart citing a 2015 study published in Science.

Other studies have documented the disappearance of pika from the Black Rock Range in Nevada and Zion National Park in Utah.

By 2050, Stewart predicts that 97 percent of the habitat suitable for pikas in Lake Tahoe will become too warm for the rodents.

In July, UC Davis released its annual State of the Lake Report, which showed Lake Tahoe is warming at 14 times the historic average.

"I think the pika can be an ambassador species for species that are vulnerable to climate change," Stewart said. "I hope that putting this out there and getting people talking contributes to the political will to take action."

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