According to theoretical predictions endothermic homeotherms can be classified as either thermal specialists and thermal generalists. In high cost environments thermal specialists are supposed to be more prone to use facultative heterothermy than generalists. We tested this hypothesis on the intraspecific level using laboratory male mice (C57BL/cmdb) fasted under different thermal conditions (20 and 10°C), and for different time periods (12-48 h). We predicted that variability of body temperature (Tb) and time spent with Tb below normothermy increase with the increase of environmental demands (duration of fasting and cold). To verify the above prediction, we measured Tb and energy expenditure of fasted mice. We did not record torpor bouts but we found that variations in Tb and time spent in hypothermia increased with environmental demands. In response to fasting, mice also decreased their energy expenditure. Moreover, we found that animals that showed more precise thermoregulation when fed, had more variable Tb when fasted. We postulate that the prediction of the thermoregulatory generalist-specialist trade-off can be applied on the intraspecific level, offering a valid tool to seek for mechanistic explanations of the differences in animal responses to variations in energy supply.
- Received March 28, 2017.
- Accepted April 12, 2017.
- © 2017. Published by The Company of Biologists Ltd