Evolved increases in running performance in cold hypoxia in high-altitude deer mice

Area of Science:

• Physiology
• Evolutionary Biology
• Animal Science

Background:

• High altitudes present challenges for small endotherms due to cold and hypoxia, impacting energy demands for locomotion and thermoregulation.
• Understanding adaptations in high-altitude natives is crucial for comprehending survival strategies in extreme environments.

Purpose of the Study:

• To investigate how high-altitude native deer mice (Peromyscus maniculatus) overcome the challenges of cold and hypoxia through evolved or plastic improvements in locomotory performance.
• To compare the running endurance of high- and low-altitude deer mice under different environmental conditions.

Main Methods:

• Deer mice from high and low altitudes were raised in captivity and acclimated to either warm normoxia or cold hypoxia.
• Running endurance was measured in both warm normoxia and cold hypoxia for all groups.
• Body temperature changes during running in cold hypoxia were monitored.

Main Results:

• High-altitude mice showed greater running endurance than low-altitude mice when acclimated to warm normoxia.
• Acclimation to cold hypoxia improved endurance in low-altitude mice, nearing high-altitude levels.
• Low-altitude mice experienced body temperature declines during cold hypoxia running, while high-altitude mice maintained body temperature better.

Conclusions:

• Evolved thermoregulatory abilities and muscle phenotypes contribute to superior locomotory performance in high-altitude deer mice under cold hypoxia.
• Plasticity through acclimation can partially mitigate the negative effects of cold hypoxia in low-altitude populations.