Thermoregulatory strategy shapes physiological responses to dormancy in animals: A meta‐analysis

Abstract Dormancy allows animals to persist through prolonged periods of unfavourable environmental conditions by entering states of extreme metabolic depression. However, physiological responses to dormancy vary substantially across taxa and can involve changes in redox balance, immune function and endocrine adjustments. A key unresolved question is whether this variation reflects fundamental differences in how endotherms and ectotherms regulate metabolic depression and subsequent reactivation, with implications for understanding animal life histories and responses to climate change. Here, we conducted a meta‐analysis to test whether physiological responses to dormancy differ between endothermic and ectothermic animals. We synthesised 2464 effect sizes from 106 studies across 57 species, quantifying redox, immune and glucocorticoid status during dormant and arousal states relative to active, non‐dormant state, under cold‐ and heat‐induced dormancy. In endotherms, dormant and arousal states were associated with reduced oxidative damage and reactive oxygen species production, together with increased antioxidant and redox‐regulatory activity, indicating robust maintenance of redox homeostasis across metabolic transitions. In contrast, ectotherms experienced increased oxidative damage during the dormant state under both cold‐ and heat‐induced conditions, with little evidence for compensatory antioxidant responses. Immune function also diverged across thermoregulatory strategies: while endotherms showed no overall suppression of immune function during dormancy and an increase in innate immune responses during arousal, ectotherms tended to downregulate both innate and adaptive pathways during the dormant state. By contrast, glucocorticoid levels did not show consistent changes across dormancy states in either group. Our study shows that the physiological consequences of animal dormancy vary across thermoregulatory strategies. Endothermy seems to buffer the oxidative and immunological challenges associated with metabolic depression, whereas dormancy in ectotherms is associated with physiological trade‐offs that may limit adaptive capacity to changing conditions. Our synthesis highlights metabolic depression as a key axis linking thermoregulation to variation in physiology, with implications for the evolution of life histories and prediction of species responses to ongoing environmental change. Read the free Plain Language Summary for this article on the Journal blog.