Staying Cool: Hot Desert Animals (page 2)
To determine how having large ears helps hot desert animals cool off.
- 2 washcloths
- index card
- Lay your arm on a table with the palm of your hand facing up.
- Fold the washcloths in half twice. Place the two washcloths over your arm, leaving a very small crack between them.
- Use the index card to fan the area of your exposed skin between the washcloths. Notice how cool the skin on your arm feels.
- Separate the washcloths so there are about 3 inches (7.5 cm) of exposed skin between them.
- Repeat step 3.
Your arm feels cooler when there is a larger space between the washcloths.
Fanning the index card does not lower the temperature of the air, but it does move the air away from your skin. The layer of air next to your skin absorbs heat from your body. When you fan the air, this warmed air next to your skin is moved away, and cooler air takes its place. More heat is lost from your skin as it heats this air. Continued fanning continues this cycle of heat being lost from your skin. A similar cooling cycle occurs when a breeze blows on the oversized ears of some desert animals. Blood vessels in the ears are just under the skin. When air blows across this animal's ears, heat is transferred from the blood in the ears to the air above the ears, and the animal's blood is cooled. The cooled blood circulates through the animal's body as warmer blood moves to the ears and is cooled. In this experiment, the greater the surface area of skin that you fanned, the cooler your arm felt. The same is true for desert animals—the larger their ears, the more heat they lose and the cooler they become. This is also why animals that live in cold environments generally have tiny ears, so they do not lose so much heat.
More Fun With Staying Cool!
Although many desert animals, such as the elf owl, kit fox, pack rat, and scorpion are nocturnal animals (feed at night), some are diurnal animals (feed during the day), such as the ground squirrel. Ground squirrels feed in the early morning and late afternoon, but they return frequently to their burrows to cool off and remain underground during the hottest part of the day. Ground squirrels also use their long bushy tails to provide shade. To provide shade a squirrel will flip its tail above its head and use it much like an umbrella or a hat. Make your own hat to keep you cool on a sunny day by following these steps:
- Fold a 20-by-20-inch (50-by-50-cm) square of colored paper, such as colorful wrapping paper, in half. Fold the paper in half again but in the opposite direction
- Use a pencil to draw a curve on the folded paper, as shown. Cut along the curve, cutting through all four layers of paper.
- Unfold the paper and cut along one of the folded lines to the center of the circle.
- Overlap and tape the edges of the circle to form a cone hat.
- Cobb, Vicki. This Place Is Dry. New York: Walker and Company, 1989. Facts about what it is like to live in the Sonoran desert in Arizona, including the plant life there.
- Ross, Kathy, and Sharon Lane Holm. Crafts for Kids Who Are Wild About Deserts. Boston: The Horn Book Inc., 1999. A craft book with instructions for making desert animal and plant models.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.