The vanishing pikas of Lake Tahoe

Some like it cold: Pikas are adapted to cold, but not for heat. Photo/Erik Beever, USGS.

As Bay Area sizzles, pika in mountains above Lake Tahoe are disappearing

LAKE TAHOE, Calif. – Mark Twain is supposed to have said that the coldest winter he ever spent was in San Francisco. Actually, he probably said something like that about Paris, but not San Francisco.

No matter. San Francisco has been hot lately, 106 degrees on Sept. 1, the highest recording in almost 150 years of recordings.

To the east in the Sierra Nevada, it’s also been hot. But a new study published in August suggested the rising warmth may have already driven out a cold-loving critter, the hamster-size pika.

A six-year study in a 165-square-mile area of the Sierra Nevada near Lake Tahoe found no recent evidence of pikas. The research team led by biologist Joseph Stewart had begun 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 told the Tahoe Daily Tribune. “The next six years we surveyed at progressively higher and higher elevations until we realized that, oh my god, pikas are extinct (extirpated) from this whole huge area.”

Pikas are adapted to surviving in cold, snowy winters. Pikas don’t hibernate. Their thick coats of fur and a high metabolic rate that acts as a furnace allow their survival in cold weather.

Those adaptations, so useful for surviving cold, make them vulnerable to overheating.

“There are thermal physiological studies that show their upper critical limit is only 3 degrees C above their resting body temperature,” Stewart explained. “So, they are very well adapted to surviving under the snow in the wintertime.”

Stewart believes the pikas in the study area may have died of hyperthermia from foraging in conditions that were too hot. Or, possibly, they did not collect enough food due to the warmer temperatures and ended up starving or not reproducing.

While pikas disappear from the mountains above Lake Tahoe, scientists continue to ponder how much wildfire risk is increased by rising temperatures.

This year’s weather will eventually become the norm, Michael Anderson, the California state climatologist, told the Sacramento Bee.

“We’ve had hot summers in the past, but as the world warms you spend more time above certain (temperature) thresholds,” Anderson said.

“There’s no one event that’s going to be a flashing sign saying, ‘Climate change did this.’ It’s just the background upon which these events start playing out. We’re in a warmer world than we were back in, say, 1991.”

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About Allen Best

Allen Best is a Colorado-based journalist. He publishes a subscription-based e-zine called Mountain Town News, portions of which are published on the website of the same name, and also writes for a variety of newspapers and magazines.
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