The range for the mountain-dwelling herbivore is decreasing in southern Utah, northeastern California and in the Great Basin that covers most of Nevada and parts of Utah, Oregon, Idaho and California, the federal agency concluded after studying the cuddly looking critter from 2012-2015.

This study's conclusion marks a more authoritative statement about the role of global warming on the animal compared to research released in 2003 that found climate change was at least partly contributing to the animal's decline.

“The longer we go along, the evidence continues to suggest that climate is the single strongest factor,” said Erik Beever, a research ecologist with the U.S. Geological Survey and lead author.

The pika's habitat on mountain slopes, known as talus, are hotter and drier in the summer and more harsh in the winter with less snowpack to serve as an insulator, Beever said.

The study bolsters the case for wildlife advocacy groups pushing for years to have the animal added to the endangered species list amid concerns about global warming.

Noah Greenwald, the Center for Biological Diversity's endangered species director, said the new research confirms that climate change is putting the animal at real risk. He said it should help with future petitions to have the animal declared endangered - something he says is necessary to ensure future generations are treated to seeing the critters during mountain hikes.

Pikas were not found in 11 of 29 sites where it once lived in northeastern California.

In the Great Basin, which stretches from Utah's Wasatch Mountains in the east to the Sierra Nevada and Cascade Mountains in the west, the population is down about 44 percent compared to historical records.

“It's not that they've just moved, they are gone all together,” Beever said. AP