<div>To investigate the relationship between the energy strategies in response to food restriction and the levels of metabolism in small mammals, body mass, resting metabolic rate (RMR), nonshivering thermogenesis (NST) and cytochrome c oxidase (COX) activity were measured in Apodemus chevrieri that were subjected to different levels of food restriction (FR). The results showed that cold-exposed group had significantly increased RMR and NST, but decreased body mass and survival rate after being restricted to 80% of ad libitum food intake compared with their counterparts maintained at room temperature. A. chevrieri with higher RMR consumed higher food intake than individuals with lower RMR, whereas no differences were observed in body mass and survival rate between two groups after being restricted to 80% of ad libitum food intake. The results suggest that A. chevrieri characterized by higher levels of metabolism are sensitive to periods of FR, providing a support for the &ldquo;metabolism switch hypothesis&rdquo;.</div>

<div>Effects of food restriction on energy metabolism in male Apodemus chevrieri from Hengduan mountain region of China</div>

Background: Ambient temperature is one of the important factors affecting the survival of small mammals in the wild and different animals have different ways of regulating when face the same environmental temperature and different temperatures will also make the same species adjust the energy budget. Therefore, it is helpful to further understand the survival and adaptation patterns of different animals to study the different adjustment modes of animals in the same region in the face of high temperature environment. 
 
Methods: In the present study, three rodents, Apodemus chevrieri, Eothenomys miletus and E. olitor, were exposed to a high temperature (Ta) of 30&deg;C for 28 days. And then body mass, body temperature (Tb), resting metabolic rate (RMR) and thermal conductance (C) were measured at Ta from 5&deg;C to 35&deg;C. 
 
Result: The results showed that Tb of all three mammals increased significantly with the increase of Ta. And thermal neutral zones (TNZ) among three animals were all 25&deg;C-30&deg;C. Moreover, RMR increased with the increase of Ta above the upper critical temperature Within the range of 30&deg;C to 35&deg;C. C values in three mammals maintained stable within the Ta of 5&deg;C-25&deg;C, which increased with the increase of Ta above 25&deg;C. All of the results suggested that three sympatric rodent species raised their Tb, narrowed their TNZ and changed C values to adapt to the high temperature. Moreover, change amplitudes of thermoregulation characteristics in E. olitor were small, indicating that E. olitor may have the strong adaptability under high temperature acclimation.

Comparative Study of Thermoregulatory and Thermogenic Characteristics of Three Sympatric Rodent Species: The Impact of High-temperature Acclimation