又稱夏眠.動物休眠的一種.動物對炎熱季節的一種適應現象.變溫動物對於炎熱的氣溫和乾燥環境有明顯的適應方式，即體溫下降，陷入沉睡狀態，如南美肺魚（Ｌｅｐｉｄｏｓｉｒｅｎｐａｒａｄｏｘａ）當水池乾涸時，鑽入淤泥之中，由鰓呼吸轉變為以鰾呼吸空氣，代謝降低，行動遲緩，陷入麻木狀態.當旱期過後，即恢復其活力，進行生殖，若整年雨水充沛，南美肺魚則不進入休眠狀態.又如夏眠時的劍螈（Ｅｎｓａｔｉｎａ）將其放在濕土上，幾小時后，皮膚吸水，體重大大增加，即夏眠出蟄.所以乾旱和高溫是夏眠的主要誘因.其他如非洲肺魚、沙蜥、草原龜均有夏眠.除變溫動物外，異溫動物有的也有夏眠，如黃鼠（Ｃｉｔｅｌｕｓ）。GOOGLE英文翻譯:Also known as estivation. Animals, a kind of hibernation. Animals to the hot season, an adaptation phenomenon. Cold-blooded animal for the hot temperatures and dry environment, a clear adaptation methods, namely, the temperature drops, into a sleeping state, such as the South American lungfish (Lepidosirenparadoxa) When the pond dried up, the drill into the mud among the transition from gill respiration to swim bladder breathing, metabolism, reduce and slow, into a numb state. When the drought period, that is to restore its vitality, reproductive, if the whole year is plenty of rain South American lungfish are not into hibernation. Another example is when the sword aestivation salamander (Ensatina) put it in wet soil, on a few hours later, skin absorption, body weight increased significantly, ie aestivation out of hibernation. Therefore, drought and high temperatures are aestivation of the the major factor. Others such as the African lungfish, sand lizards, turtles are aestivation grassland. In addition to cold-blooded animal, the different temperature and some animals also have aestivation, such as the ground squirrel (Citelus).