Heterothermy

Heterothermy (from Greek: heteros = "other" thermē = "heat.") is a physiological term for animals that exhibit characteristics of both poikilothermy and homeothermy.

Heterothermy or heterothermia refers to animals that can switch between poikilothermic and homeothermic strategies. These changes in strategies typically occur on a daily basis or on an annual basis. More often than not, it is used as a way to dissociate the fluctuating metabolic rates seen in some small mammals and birds (e.g. bats and hummingbirds), from those of traditional cold blooded animals. In many bat species, body temperature and metabolic rate are elevated only during activity. When at rest, these animals reduce their metabolisms drastically, which results in their body temperature dropping to that of the surrounding environment. This makes them homeothermic when active, and poikilothermic when at rest. This phenomenon has been termed 'daily torpor' and was intensively studied in the Djungarian hamster. During the hibernation season, this animal shows strongly reduced metabolism each day during the rest phase while they revert to endothermic metabolism during their active phase, leading to normal euthermic body temperatures (around 38C).