Effects of animal dormancy on oxidative stress, immune status, and glucocorticoids: a meta-analysis

Despite the growing interest of evolutionary biologists and ecologists in unravelling the mechanisms behind animal responses to challenging conditions, our knowledge remains limited. To contribute to this field, we conducted a global meta-analysis (N= 112 unique studies, k = 2,840 independent estimates) to synthesize empirical information on the influence of vertebrate dormancy (i.e., cold- and heat-induced dormancy) on redox status, immune function, and glucocorticoid levels. Our study reveals that dormancy has contrasting effects on animal physiology, depending on the thermoregulatory strategy. In endotherms, both dormant and arousal states are accompanied by reduced ROS production, lower oxidative damage, or upregulated antioxidant response, whereas in ectotherms, greater oxidative damage occurs only during the dormant state. Likewise, innate immune responses are upregulated during arousal in endotherms, while ectotherms downregulate pathways involved both in innate and adaptive responses during the dormant state. Interestingly, glucocorticoid levels remain stable throughout dormancy, suggesting that undergoing metabolic shifts may uncouple glucocorticoid release. These findings provide mechanistic explanation on the eco-evolutionary consequences of dormancy, revealing diverging strategies between endotherms and ectotherms. By highlighting metabolic depression as a central axis of these responses, our results also inform conservation strategies for dormant species facing rapid environmental change.