Winter on the Qinghai-Tibetan plateau is unfriendly to pikas. Temperatures in barren, windy mountains usually drop below -30 ° Celsius, and the grass that normally sustains rabbit mammals becomes dry and brittle. It would seem the perfect time for these critters to hibernate or subsist in grass tents in burrows to stay warm, like the American pika.
In contrast, the plateau pika (Ochotona curzoniae) continues to search for food in the winter, but reduces its metabolism by 30 percent to save energy, the researchers reported on July 19 in the Proceedings of the National Academy of Sciences. Some pikas also resort to unusual rations: yak poop.
Data from four-site cameras confirmed that pikas regularly face the cold to feed. “Clearly they’re doing something smart with their metabolism that isn’t hibernation,” says John Speakman, an ecophysiologist at the University of Aberdeen in Scotland.
Speakman and colleagues measured the daily energy expenditure of 156 pikas of the plateau in summer and winter and implanted 27 animals with temperature sensors. While many non-hibernating animals warm up in the winter using more energy, these pikas did the opposite (SN: 22/01/14). On average, spikes reduced their metabolism by 29.7 percent, in part by cooling their bodies a couple of degrees overnight. Animals were also less active, relative to summer levels.
But in sites with yaks, pikas were more abundant but even less active. That baffled investigators "until we found a kind of half-eaten yak Turk in one of the burrows," Speakman says. Eating excrement can cause illness. But with few options, yak poop could be an abundant and easily digestible food that “massively reduces the amount of time (pikas) you need to spend on the surface,” he says.
The researchers captured spikes scarring scat on video and DNA testing of stomach contents solidified that this behavior is common. It remains to be seen whether eating in manure has disadvantages, but it is clear that not being very picky compensates for the pika.
When pika and yak overlap, rabbit-like mammals (shown) find an abundant and easily digestible food source in the yak’s feces. Eating the excrement helps the goosebumps, which do not hibernate, survive during the harsh winter months on the Qinghai-Tibetan Plateau.