Estivaatio

Estivaatio, from Latin aestivatio meaning summer, is a state of dormancy or torpor that some animals enter during hot, dry periods to survive unfavorable environmental conditions. In estivation, metabolic rate is reduced, activity slows markedly, and water loss is minimized, allowing survival through drought and heat. It is analogous to hibernation but occurs in summer and is driven by heat and desiccation rather than cold.

Estivation is observed across a range of taxa, including amphibians, reptiles, mollusks, fish and some invertebrates. Many land snails and other mollusks estivate by secreting a mucus layer and sealing the opening of their shells (epiphragm) to prevent water loss. Some aquatic and terrestrial snails form mucus cocoons. Vertebrates such as certain toads and frogs may burrow into moist soil and greatly reduce activity, while some desert and tropical reptiles retreat to burrows or shaded locations. African lungfish (and other species in arid environments) can induce a mucus cocoon around themselves to survive months of drought. Insects and other invertebrates may enter a drought-induced quiescence or diapause that serves a similar functional purpose.

Estivation represents a key adaptation to seasonal or extreme climates, enabling survival during prolonged heat and dryness. It is a topic of study in physiology, ecology and evolutionary biology, contributing to understanding how organisms cope with water loss and temperature stress, and informing perspectives on climate change and biodiversity in arid and semi-arid regions.