期刊
出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2100707118
关键词
winter survival; metabolic suppression; thyroid axis
资金
- National Natural Science Foundation of China [31670394, 31570410]
- strategic program of the Chinese Academy of Sciences [XDB13030100]
- National Key Research and Development Program of China [2016YFC050190504]
- Royal Society
- National Science Foundation of China [NSFC-RS 30711130224]
- President's International Fellowship Initiative professorial fel-lowship program
- Wolfson merit award
- PIFI2017 (Presidents International Fellowship Initiative 2017)
The plateau pikas on the Qinghai-Tibetan Plateau survive the harsh winter conditions by suppressing metabolism, lowering body temperature, reducing activity, and supplementing their food intake with yak feces. This interspecific coprophagy allows pikas to thrive in areas with higher densities of domestic yaks, their supposed competitors for food.
The Qinghai-Tibetan Plateau, with low precipitation, low oxygen partial pressure, and temperatures routinely dropping below -30 degrees C in winter, presents several physiological challenges to its fauna. Yet it is home to many endemic mammalian species, including the plateau pika (Ochotona curzoniae). How these small animals that are incapable of hibernation survive the winter is an enigma. Measurements of daily energy expenditure (DEE) using the doubly labeled water method show that pikas suppress their DEE during winter. At the same body weight, pikas in winter expend 29.7% less than in summer, despite ambient temperatures being approximately 25 degrees C lower. Combined with resting metabolic rates (RMRs), this gives them an exceptionally low metabolic scope in winter (DEE/RMRt = 1.60 +/- 0.30; RMRt is resting metabolic rate at thermoneutrality). Using implanted body temperature loggers and filming in the wild, we show that this is achieved by reducing body temperature and physical activity. Thyroid hormone (T3 and T4) measurements indicate this metabolic suppression is probably mediated via the thyroid axis. Winter activity was lower at sites where domestic yak (Bos grunniens) densities were higher. Pikas supplement their food intake at these sites by eating yak feces, demonstrated by direct observation, identification of yak DNA in pika stomach contents, and greater convergence in the yak/pika microbiotas in winter. This interspecific coprophagy allows pikas to thrive where yak are abundant and partially explains why pika densities are higher where domestic yak, their supposed direct competitors for food, are more abundant.
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