Body Temperature Frequency Distributions: A Tool for Assessing Thermal Performance in Endotherms?

Area of Science:

• Physiology
• Thermoregulation
• Comparative Biology

Background:

• Endotherms exhibit varying degrees of body temperature flexibility, from strict homeothermy to hibernation.
• Previous analyses of this variability within thermal performance curve frameworks are limited.

Purpose of the Study:

• To investigate if frequency distribution histograms of continuous body temperature measurements can serve as an analogue to thermal performance curves in endotherms.
• To analyze thermoregulatory phenotypes across diverse mammal species.

Main Methods:

• Collected continuous core body temperature data from mammals with varied thermoregulatory strategies.
• Analyzed temperature data using frequency distribution histograms.
• Decomposed body temperature traces into active/rest phase modes, spreads, and skew.

Main Results:

• No analogous patterns to ectotherm thermal performance curves were found in full datasets or component analyses.
• Most mammal species displayed bimodal or right-skewed body temperature distributions for both active and rest phases.
• Results suggest mammals tolerate elevated body temperatures more than commonly assumed.

Conclusions:

• Core body temperature distributions may aid in determining optimal temperatures for thermal performance studies and ecological applications.
• Body temperature distributions are not ideal for assessing the shape and breadth of thermal performance in endotherms.
• Researchers should consider the full range of active and resting temperatures in endotherms, not just mean values.