In some mountain ranges, Earth's warming climate drives rabbit relatives known as pikas to higher elevations--or wipes them out.
But biologists discovered that pikas living in rockslides near sea level in Oregon can survive hot weather by eating moss.
"Pikas eat foods like moss to persist in warming environments," says biologist Denise Dearing of the University of Utah, co-author of a new paper reporting the results. The paper is published online today in the Journal of Mammalogy.
Jo Varner, also a biologist at the University of Utah and a paper co-author, says that although "some fiber is good, moss is 80 percent fiber. It's a bit like eating paper.
"By consuming mosses that grow on the rockslides where they live, the pikas don't have to forage outside the shady heat-buffer of the rocks.
"Few herbivores consume moss because it's so nutritionally deficient. These pikas set a new record for moss in a mammal's diet: 60 percent."
Pikas' extensive moss-eating "suggests that they may be more resistant to climate change than we thought," says Dearing.
The biologists, whose research was funded by the National Science Foundation (NSF), believe they know why.
Like rabbits and hares, pikas produce a fraction of their feces in the form of caecal (pronounced see-cull) pellets, and reingest them to gain nutrition.
"Pikas and rabbits--and their gut microbes--are the ultimate recycling factory," Dearing says. "They ingest low-quality food over and over again, and turn it into high-quality protein and energy. The end product is six times more nutritious than the moss" that started it all.
The order Lagomorpha, to which pikas belong, has two families: one is made up of rabbits and hares, the other of pikas.
Pikas are native to cold, alpine climates--often above 8,200 feet--in North America, Asia and Eastern Europe.
Pikas are very sensitive to heat, dying if they spend more than two hours above 78 degrees Fahrenheit.
In parts of the West--including Nevada, Oregon and Colorado--pikas have gone extinct in some mountain ranges and moved to higher peaks in others.
Pikas live as high as 11,230 feet on the slopes of Mount Hood east of Portland, Ore. They also live thousands of feet down the north slope of Mount Hood in the wet, foggy Columbia River Gorge.
How do they exist in warmer places like the gorge? By living in rocks on moss-covered slopes, the researchers found.
The scientists conducted their study on two such slopes near Wyeth, Ore., from June through August, 2011 and 2012. Pikas are most active in the summer months.
The biologists surveyed the abundance of mosses, lichens, ferns, grasses, sedges, rushes, forbs, shrubs and trees in the rockslides. They found that the slopes were 60 percent to 70 percent covered by vegetation.
Samples of the pikas' food were analyzed for how much the animals ate, and for the food's nutrition and fiber content.
Sixty percent of the pikas' diet by dry weight came from mosses. The pikas favored two species: hoary rock moss and big red-stem moss.
"This study represents the highest degree of voluntary moss consumption reported for a mammalian herbivore in the wild," Dearing and Varner write in their paper.
For temperature-sensitive pikas, cool, green mosses--whether atop a mountain or at the bottom of a gorge--are life-rings.
The research was also funded by the University of Utah, Wilderness Society, Southwestern Association of Naturalists, Society for Integrative and Comparative Biology, and American Society of Mammalogists.