抄録
There are some animals which live in the high-altitude and cold environments. To learn how the wild animals adapt to and survive in such extreme environments is an important and useful approach not only for the progress of science but also for health promotion and prosperity of the human. The pika, Ochotona, living in cold zone or in high mountains prefers the low temperatures and is considered to be remained species of the glacial periods. The pika's high body temperature, high metabolic rate and high fur insulation are advantageous for survival in the cold. The pika's unique behavioral strategies to adapt to cold are living in burrows under the ground or in the shelter among rocks and hoarding grasses for winter foods. The pika do not hibernate, though many mammals living nearby hibernate. On the other hand, the pika is heat intolerant due to poor heat loss ability such as poor panting, small ear pinnae and the absence of thermal salivation. The pikas reared in the laboratory showed neither diurnal nor nocturnal body temperature rhythm. Our fieldwork using bio-telemetry devices in their natural habitat in Qinghai, China demonstrated that the pikas are essentially diurnal. Taking the ecologists' field observation together into consideration, it is suggested that the pikas may vary their activity rhythm from diurnal in the relatively cool environment to a crepuscular (dawn and dusk) pattern in the relatively hot environment to avoid the heat during midday. The pika is also of interesting because of its communication with calls and its territorial social organization. [Jpn J Physiol 55 Suppl:S65 (2005)]
