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To avoid the harsh temperatures and the lack of food that accompany the cold, some animals migrate. Others hibernate. But the pikas of the Qinghai-Tibetan Plateau in northwest China do neither.
Pikas are pint-sized, rodent-like mammals that look like a cross between a guinea pig and a rabbit. Of the 29 species in the world, the American pika, native to the western United States and Canada, is well known for the way it collects plants in its mouth before hiding food stores underground to support Winter.
But how its Asian parent, the plateau pika, survives in the dry, wind-blown steppes, where temperatures regularly drop to minus 20 degrees Fahrenheit (minus 29 degrees Celsius) and plants shrivel up in winter, has long been an issue. mystery. Unlike other animals in cold weather, pikas cannot rely on fat, weight gain in the winter, or sleep in the cold months. (Learn about another teddy bear-headed pika rediscovered in China.)
Now, after 13 years of research, scientists say they have discovered the secret to the survival of the plateau pika: animals slow down their metabolism and supplement their usual plant diet with yak droppings, which contain valuable undigested nutrients. .
The first part of the formula makes sense, because a reduced metabolism means pets need to get fewer calories each day. But the second part was more surprising for the researchers.
“At first, no one we spoke to believed the story that they ate the yak droppings,” said study leader John Speakman, a physiologist at the University of Aberdeen in Scotland, in an email.
“The accumulated evidence, however, is now indisputable,” says Speakman, whose study was published today in the Proceedings of the National Academy of Sciences.
This behavior, known as interspecific coprophagia, is quite rare in vertebrates. Speakman believes yak waste is likely an abundant, low-effort food source that allows pikas to both save energy and stay safe from predators, such as peregrine falcons and foxes. Tibetans.
Beneficial bacteria
In 2009, Speakman found a half-eaten yak falling into the burrow of a plateau pika, triggering his curiosity. “Then I really started to think: this is weird. Maybe they eat this stuff.” Then a year later, when two pika accidentally died in a trap, an analysis of their intestines revealed the presence of yak droppings.
To prove the theory, Speakman and his colleagues analyzed the intestinal contents of more than 300 deceased plateau pikas – collected for another study in 2018 and 2019 – and found that about 22% of the sample contained DNA. of yak. This is probably an underestimate because DNA breaks down when feces are exposed to the sun, he says.
Another round of tests found that in winter, the composition of pikas’ microbiomes changes to resemble that of yaks, suggesting that animals may also acquire beneficial bacteria from yak droppings.
In 2017 and 2018, scientists captured a freehand video of plateau pikas eating yak droppings on four occasions. Together, these different pieces of evidence confirm coprophagia. (Read how wild yaks can climb higher due to climate change.)
Coprophagia may also be the reason why plateau pikas tend to be more abundant in areas inhabited by yaks. Cattle ranchers view pikas as direct competitors for food and poison animals by the millions, Speakman says.
“However, things are changing and more recent attempts to control them have investigated the use of contraceptives, which have less collateral damage” for other species, he adds.
Scat heard around the world
“For 30 years, I’ve been lecturing on pikas and talking about how the American pika collects groundhog droppings in their hay piles, in the hope that someone in the audience will tell me why,” Chris Ray, quantitative environmentalist at the University of Colorado Boulder, said in an email.
There is as yet no evidence of parallels between the coprophagia of Central Asian Plateau pikas and the behavior of American pikas. But the new study “rocked” his thinking about the potential importance of groundhog litter to the American pika, a species in decline in the western United States due to rising temperatures, says Ray.
“I live in the Rocky Mountains so I know how cold winters are where some pikas live, and I was taken aback by how they manage to survive.”
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