Learn

How do animals keep cool without air conditioning?

Animals use clever tricks: drying water, big ears, shade, digging and good timing. Houses use some of the very same ideas.

The one big rule of cooling

Heat always moves from a warmer thing to a cooler thing. A hot animal has to get its extra heat out of its body and into something cooler, like the air, the ground or water. Every trick on this page is a way to move heat out, or keep heat from getting in.

Meet the animal cooling crew

🐕 Dogs: the panting pros

Dogs have only a few sweat spots, on the pads of their paws. Fur covers the rest, so sweat could not dry well anyway. Instead, dogs pant. They take quick, short puffs with their tongue out. Air rushes over the wet tongue and mouth. The wetness dries, and drying takes heat away with it.

House match: Inside your air conditioner is a cold metal part called the evaporator coil. A special fluid called refrigerant boils inside it and soaks up heat from your home’s air, kind of like the drying water on a dog’s tongue soaks up heat. Learn more on How Air Conditioning Works.

🐇 Jackrabbits: ears like radiators

Black-tailed jackrabbits live in hot, dry parts of Texas. Their ears are huge, thin and full of tiny blood tubes. When the jackrabbit is warm, extra blood flows into its ears. If the air is cooler than its body, the heat slips out of the ears and into the air. That way it cools off without using up much water.

House match: The outdoor part of an AC has thin metal fins wrapped around tubes. Hot refrigerant flows through the tubes, and the fins pass the heat into the outside air. Big, thin, spread-out surfaces are great at getting rid of heat, whether they are ears or fins.

🦇 Mexican free-tailed bats: night flyers with built-in vents

Austin’s famous bats from the Congress Avenue Bridge rest all day in narrow, shady cracks under the bridge. At dusk they fly out to hunt. Flying makes a lot of body heat. Scientists found that these bats have bare patches near the sides of their bodies and on their wings with lots of tiny blood tubes. Warm blood flows there to give off heat while they fly. When the air high up is cold, they send less blood there to stay warm.

House match: Your heating and cooling system works like that too. It sends cooled or warmed air where it is needed through ducts (big hidden tubes, in Austin usually up in the attic) and out the vents in the ceiling.

🕳️ Armadillos: change the schedule

Nine-banded armadillos have very little fur and can’t handle much heat or cold. So they change when they come out. In summer, they are busy at night when it is cooler. In winter, they come out in the warmest part of the day. The rest of the time they rest in burrows (holes they dig in the ground), where the temperature stays steadier.

House match: Grown-ups can use a programmable thermostat to change the home’s settings at different times of day. And the ground under and around a house stays steadier than the air, a bit like an armadillo’s burrow.

🦎 Texas horned lizards: sun in the morning, shade in the afternoon

Lizards can’t make much of their own body heat, so they borrow it from the sun. In the morning, a Texas horned lizard sits in the sun to warm up. As the day gets hot, it moves into shade, under plants or rocks, or into a burrow. At night it may dig into loose soil. It moves to the right spot at the right time, all day long.

House match: Curtains and shade trees let your family do the same thing. Let the sun in on cold winter days. Block it on hot summer afternoons. See Shade Squad.

Compare the tricks

Try it: the wet-wrist test

1. You need a little tap water and a spoon.
2. Put a few drops of water on the back of one wrist. Keep the other wrist dry.
3. Gently blow on both wrists, or wave them in the air.
4. Which one feels cooler? The wet one! The drying water is carrying heat away, just like a panting dog.

Keep exploring