Animals whose body temperature varies according to the environment are known as cold-blooded animals. For example, fish are cold-blooded, so are amphibians and reptiles. These cold-blooded animals cannot control their body temperature.
They get their heat from the outside environment due to that their body temperature fluctuates according to external temperature. For example, if the outside temperature is -10 oC, their body temperature drops to -10 oC and if it increases to 100 oC, their body temperature will rise to 100 oC. Therefore it is necessary for cold-blooded animals to live in certain areas for survival and become sluggish in cold weather. That’s why cold-blooded creatures are not found in cold environments such as Polar Regions.