Why do mammals have warm blood but reptiles have cold blood?

They do this by generating their own heat when they are in a cooler environment, and by cooling themselves when they are in a hotter environment. To generate heat, warm-blooded animals convert the food that they eat into energy. read more

Mammals are warm blooded animals as they have homeostatic mechanism , where the body keeps or maintains its own temperature, blood pressure at a constant levels according to the environment. Whereas, reptiles are poikilothermic in nature as they cannot regulate body temperature of its own, hence called cold blooded animals. read more

Mammals and even insects, such as bees, mimic traits of thermoregulation by seeking out warmth or cold. However, unlike reptiles, amphibians, insects, and other cold-blooded animals, mammals are not able to inherently regulate their body temperatures. read more

A supposedly ‘cold-blooded’ reptile will, on most days, have warm blood simply because that reptile will be doing anything in its power to keep itself warm, by basking or resting on something warm. read more