The American pika, a small mammal adapted to high altitudes and cold temperatures, has died out from a 165-square-mile span of habitat in California’s northern Sierra Nevada mountains, and the cause appears to be climate change. Researchers surveyed pika habitat throughout the north Lake Tahoe area and found that pikas had disappeared from an area that stretches from near Tahoe City to Truckee, more than 10 miles away, and includes Mount Pluto.