It has been years since any have been spotted in the wilderness around Idyllwild, Calif., in the southernmost of the two Southern California mountain ranges where they have been documented since the 1800s, The (Riverside, Calif.) Press-Enterprise reported Monday.
"They've just disappeared from our mountain range and we don't understand why," said Anne Poopatanapong, a Forest Service biologist.
The U.S. Fish and Wildlife Service has been petitioned to protect San Bernardino flying squirrels, a subset of the more plentiful northern flying squirrel that lives across much of the United States, under the Endangered Species Act.
The threats are many, the petition says, and chief among them is climate change, which shifts the squirrels' forest habitat upslope to cooler temperatures.
"They're already at higher elevations so they have limited options for moving upward," said Shaye Wolf of the Center for Biological Diversity, which brought the petition. "Eventually, they start to run out of room."