鼠兔食用大量苔藓抵抗炎热天气

In some mountain ranges, Earth's warming climate is driving rabbit relatives known as pikas（鼠兔） to higher elevations or wiping them out. But University of Utah biologists discovered that roly-poly pikas living in rockslides near sea level in Oregon can survive hot weather by eating more moss（苔藓） than any other mammal. "Our work shows pikas can eat unusual foods like moss to persist in strange environments," says biology professor Denise Dearing, senior author of the new study, published online today in the February 2014 issue of Journal of Mammalogy. "It suggests that they may be more resistant to climate change than we thought."

The study's first author, biology doctoral student Jo Varner, says: "Some fiber is good, but this is almost all fiber. Mosses are 80 percent fiber. It's a bit like eating paper."

"By consuming mosses that grow on the rockslides where they live, the pikas are released from foraging outside the safety and shady heat buffer of the rocks," where they can overheat or be killed by weasels and hawks, says Varner. "Few herbivores（食草动物） consume moss because it's so nutritionally deficient. The pikas in our study actually set a new record for moss in a mammal's diet: 60 percent."

The study also found the low-elevation pikas "build much smaller food caches to survive the winter, compared with pikas in typical high-elevation habitat," she adds. The biologists believe they know how the cute critters do it: 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. (Caecal pellets look like dark, wet blobs versus normal feces that are hard individual pellets.)

"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."

Varner says the findings suggest Northwest residents may want to preserve moss that often covers rockslides, which are known as talus slopes. Moss is collected for horticulture in some areas, and "traipsing all over rockslides and trampling moss cover has become a popular pastime in the gorge," she adds.

Funding for the study came from the National Science Foundation, University of Utah, the Wilderness Society, Southwestern Association of Naturalists, Society for Integrative and Comparative Biology, and American Society of Mammalogists.