Torpor, a state of decreased activity where the body temperature and metabolism decreases, is especially useful for bats, as they use a large amount of energy while active, depend upon an unreliable food source, and have a limited ability to store fat. They generally drop their body temperature in this state to , and may reduce their energy expenditure by 50 to 99%. Tropical bats may use it to avoid predation, by reducing the amount of time spent on foraging and thus reducing the chance of being caught by a predator. Megabats were generally believed to be homeothermic, but three species of small megabats, with a mass of about , have been known to use torpor: the common blossom bat (Syconycteris australis), the long-tongued nectar bat (Macroglossus minimus), and the eastern tube-nosed bat (Nyctimene robinsoni). Torpid states last longer in the summer for megabats than in the winter.
