Heterothermic (from Greek: hetero = "other" thermy = "heat.") is a physiological term referring to a unique case of poikilothermy. Heterothermic creatures are homeothermic for a portion of the day, or year. More often than not, it is usually used as a way to dissociate the fluctuating metabolic rates seen in some small mammals & birds (e.g. bats & hummingbirds), from those of traditional cold blooded animals.