Poikilotherm is derived from Greek “poikilos” (varied, variegated) + Greek “therme” (heat). Poikilotherm is the term used to describe any animal whose body temperature varies with the temperature of its surrounding environment. A poikilotherm or poikilothermic animal or poikilothermous animal is also known as cold-blooded animal, ectotherm, heterotherm, or allotherm. Poikilothermism or poikilothermy is the state or condition of being cold-blooded or poikilothermic. All animals except mammals and birds are poikilotherms.