Estivation or aestivation (from Latin aestas, summer), also known as "summer sleep", is a state of animal dormancy somewhat similar to hibernation. It takes place during times of heat and dryness, the hot dry season, which is often but not necessarily the summer months.
Invertebrate and vertebrate animals are known to enter this state to avoid damage from high temperatures and the risk of desiccation. Both terrestrial and aquatic animals undergo estivation.
Gastropoda: Some air-breathing land snails, including species in the genera Helix, Cernuella, Helicella and Otala, commonly estivate during periods of heat. Some species move into shaded vegetation or rubble. Others climb up tall plants, including bushes and trees, and will also climb man-made structures such as posts, fences, etc., to escape intense ground heat.
The habit of climbing vegetation to estivate has caused more than one introduced snail species to be declared an agricultural nuisance.
To seal the opening to their shell to prevent water loss, pulmonate land snails secrete a membrane of dried mucus called an epiphragm. In certain species, such as Helix pomatia, this barrier is reinforced with calcium carbonate, and thus it superficially resembles an operculum, except that it has a tiny hole to allow some oxygen exchange.
There is decrease in metabolic rate and reducing rate of water loss in aestivating snails like Rhagada tescorum, Sphincterochila boissieri and others.
Insecta: Lady beetles (Coccinellidae) have been reported to estivate.
Crustacea: Many land crabs spend dry seasons in an inactive state at the bottom of their burrows.
Reptiles and amphibians
Full article ▸