Table 1.

Examples of classical, adaptive explanations of thermoregulation or hydroregulation strategies, and their re‐interpretation in the framework of thermo‐hydroregulation

	Examples	The classical explanation	The thermo‐hydroregulation perspective
Physiological regulation in ectotherms
Metabolic depression	Downregulation of basal metabolism during acclimation to higher temperatures in lizards (Christian, Bedford, & Schultz, 1999)	Thermoregulation: Physiological and metabolic acclimation responses in order to save energy during thermoregulation	Metabolic depression is involved in both thermoregulation and the maintenance of an optimal hydration state through lower respiratory water loss
Critical thermal limits	Lethal body temperature limits of nonavian reptiles, amphibians, and insects (Angilletta, 2009)	Thermoregulation: These limits are the body temperature boundaries an individual should not pass when thermoregulating	CTLs would change if the organism is dehydrated. As heat would imply water losses, being dehydrated implies less resistance to heat
Metabolic water production	Production of water through catabolic pathways in flying insects (Chown & Nicolson, 2004)	Hydroregulation: Production of water to compensate water losses and dry food consumption	In high temperature environments, metabolic water production can overrides the water losses due to overheating and even participate in hives cooling in the case of eusocial hymenoptera
Behavioral regulation in ectotherms
Activity patterns	Aestivation in desert lizards or reduced activity during hottest hours of the day (Porter, Mitchell, Beckman, & DeWitt, 1973)	Thermoregulation: Activity time dictated by availability of optimal operative temperatures in the environment with reduced activity when operative temperatures are above the optimum	A lower activity reduces the risks of overheating and dehydration by limiting exposure to warm and dry air conditions when free‐standing water is not available
Microhabitat selection	Use of thermal microhabitat to heat or cool down in insects (Caillon et al., 2014)	Thermoregulation: Microhabitat choice driven by spatial heterogeneity in operative temperatures and constraints on movement patterns to ideally select optimal body temperatures	Microhabitat selection explained by joint optimization of water loss, heat exchanges and energy expenditure, and nonenergetic factors. If water is limiting, optimal body temperatures for heat exchanges and energy metabolism may not be reached
Posture changes	Change in the posture according to the daytime in frogs (Pough et al., 1983)	Hydroregulation: Change in water availability selects for different body postures between day and night to reduce the rate of evaporative water loss	Posture changes though time are explained by the need of optimizing heat transfers and at the same time minimizing water losses