Integrated Physioecological Adaptation of Apodemus chevrieri to Water Deprivation: Synergistic Responses in Body Mass Regulation and Water Metabolism.

As global climate change intensifies, increasing drought in Southwest China may impose strong water stress on small mammals in the Hengduan Mountains. Apodemus chevrieri is endemic to this region, but its integrated responses to water restriction remain unclear. Here, we compared control and water-stressed individuals and quantified changes in body mass, food intake, body temperature (T b), metabolic traits, evaporative water loss (EWL), metabolic water production relative to EWL (MWP/EWL), and visceral and digestive-tract morphology. Water restriction reduced body mass, food intake, core T b, and metabolic rate. It also reduced small intestine mass, but increased the size of the large intestine and cecum, indicating enhanced hindgut development. EWL increased with rising ambient temperature (T a), while MWP/EWL decreased as T a increased. Water deprivation shifted the T a at the water balance point (T a @ MWP = EWL) from 12.5 to 16°C. These results indicate that under water deprivation stress, A. chevrieri reduces water and energy expenditure by lowering body mass and T b, downregulating metabolic rate, and enhancing hindgut structure to improve water reabsorption. Interspecific comparisons further suggest that although this species generally exhibits water physiological characteristics typical of mesic habitats, it shows physiological plasticity consistent with a partial shift toward a xeric water-economy strategy under water deprivation stress. This integrated strategy reveals the adaptive potential of A. chevrieri to seasonal drought in the Hengduan Mountains.