See the Difference
Have you ever held a lizard? Its body temperature is likely lower than yours. You probably wouldn’t feel a difference. But you can see it in these images taken with a special camera. They show how much heat an object gives off.
hand
lizard
HOTTER
COLDER
This elephant cools down by fanning its ears.
This spider’s body is cooler than its environment.
Look at the image of a hand holding a lizard. The bright red of the hand shows a warm body temperature. This is true even though the air around it is cooler. The lizard shows up mostly as blue. Before being held, it was dark blue, like the background. Its body temperature was the same as the air around it.
But what happens as the lizard and the person touch? The lizard gets heat from the person’s hand. Its body is warming. Its feet and legs show up as green and yellow.
HOTTER
COLDER
This cat makes its own body heat. It leaves behind a trail of warm pawprints.
Watch as a person leaves warm footprints on a cold floor.
COLDER
HOTTER
gharial
This gharial soaks up the sun’s rays. Then its temperature begins to rise.
Food provides the materials to grow. It also repairs damaged cells. If you cut your finger, new cells grow and heal it. The new cells come from food. Food also provides energy. And energy produces heat. In this way, an animal’s body is like a furnace.
A Living Furnace
Why can some animals keep the same body temperature while others cannot? The answer is metabolism.
Metabolism is all of the chemical reactions that take place in the body. Tiny molecules combine and break apart in body cells. They form new substances. Most of this happens as food breaks down.
HOTTER
COLDER
meerkats
These meerkats don’t need to wait for the sun. They control their own body heat.
flamingos
HOTTER
COLDER
Some of these flamingos have one leg that is hotter than the other. When a flamingo stands on one leg, that leg loses heat, while the other leg is tucked up next to its body keeping warm.
The faster an animal’s metabolism, the more energy the animal has for keeping warm. An endotherm’s metabolism is fast. For birds and mammals, it is fast enough to produce constant warmth. This allows the animal to keep its body temperature high. Birds have the fastest metabolism and a body temperature of 40oC to 42oC (104oF to 108oF). Can you think of a reason why birds need a fast metabolism? Think about how birds move. The high rate of metabolism makes the energy birds need to fly.
