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Activity in a Changing Climate How "warm-blooded" animals stay warm
As soon as the air temperature falls below 27°C a naked human begins to feel cold. In order to keep their bodies warm, mammals and birds do the opposite of what they do when they want to cool down: They stop sweating, panting or licking themselves. The blood is kept in the centre of the body, to stop heat from being lost. This is why people often look pale or white when they are feeling cold. Birds and mammals grow a thicker layer of feathers or fur to prepare for winter. We wear thicker layers of clothes. Some animals will grow a layer of fat under the skin. The fat is not only an energy reserve but it is also a good insulator against the cold. Fat is very useful to animals which live in water. Shivering The muscles of the body produce a lot of heat as they contract and relax. This can be used to keep an animal warm. Making heat Some organs in our body, especially the liver and the kidneys, can respire more when we are cold. Respiration makes heat energy which is passed to the blood as it circulates through these organs. The warm blood carries heat to all the vital organs. The pie chart opposite shows where we produce the most heat in our bodies.
As you can see, when the weather is cold "warm-blooded" animals are indeed warmer than their environment. In warm weather, however, "warm-blooded" animals are colder than their environment, so the term "warm-blooded" is not very precise. It is best to remember that "warm-blooded" animals keep their body temperature constant when the weather is cold. They can do this because their bodies make heat energy from their food.
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