When the tap runs dry: The physiological effects of acute experimental dehydration in Peromyscus eremicus

The extreme aridity of desert environments results in water availability playing a role in shaping biological processes and allowing animals to persist in the environment and maintain salt and water homeostasis. However, rapid climate change can challenge this tolerance. The cactus mouse (Peromyscus eremicus) is native to the arid deserts in southwest North America. Past studies have shown that cactus mice are highly adapted to desert conditions, with efficient water retention and dehydration tolerance. Therefore, cactus mice represent an interesting experimental model to examine physiological adaptations and thresholds. Here, we present physiological adaptations that allow the desert-adapted cactus mouse to live in this extreme environment. Using data collected in a simulated desert environment with a captive colony of cactus mice, we’ve integrated lab-based experiments with long-term physiological data collection to characterize the response of water-deprivation in the desert-adapted cactus mouse. Mice without access to water had significantly lower energy expenditures and in turn, reduced water loss compared to mice with access to water after the first 24 hours of the experiment. Additionally, we observed significant weight loss likely related to dehydration anorexia an adaptive response to limit fluid loss by reducing waste and the solute load as well as allowing water reabsorption from the kidneys and gastrointestinal tract. Finally, we observed body temperature correlated with sex, with males without access to water maintaining body temperature when compared to hydrated males while body temperature decreased for females without access to water compared to hydrated, suggesting daily torpor in females.