According to the Smithsonian National Zoological Park, warm-blooded animals regulate their body heat internally, while the body temperature of cold-blooded animals depends on the temperature of their surroundings. Mammals are warm-blooded, while reptiles, insects and arachnids are not. Amphibians and fish also require external heat sources in order to live.
Warm-blooded animal species live on every continent including Antarctica. The majority of cold-blooded animals prefer warm or hot climates. When their surroundings are hot, these animals bustle with energy and speed. When the ambient temperature drops, the animals become lethargic and sluggish. This happens because cold-blooded species rely on heat-activated chemical reactions for muscle energy. The lower the temperature, the less effective the reactions are. If the temperature remains excessively cold for an extended time period, cold-blooded animals die.
According to the Cool Cosmos Project at the California Institute of Technology, warm-blooded animals have several tactics for maintaining proper body temperature. When overheated, mammals sweat, which cools the skin as it evaporates. Some mammals have body parts designed to prevent overheating. For example, elephants have huge ears that radiate heat, keeping the elephant comfortable in scorching temperatures.
In extreme cold, warm-blooded animals shiver. Some species hibernate during the coldest months, and migratory birds fly to warmer locales in late autumn and early winter. Furred mammals have thick, insulating winter coats but shed them to avoid overheating in the spring and summer.