The study identified 67 sites in the Sierra where pikas have been known to live – from the slopes of Mount Shasta in the north to the John Muir Wilderness in the south. Researchers found pikas had vanished from 10 of these spots, said Joseph Stewart, a scientist at UC Santa Cruz and the study’s lead author.

While all mammals respond to temperature changes, the pika is particularly sensitive. It dies when its body temperature rises just a bit above normal. Temperatures above 75 degrees can kill a pika in one hour.