How do animals keep cool in the desert?

In the Film

A nighttime scene shows a kangaroo rat going in and out of a burrow. The rat never drinks, but manufactures water through its metabolic processes. The rat takes advantage of ways to keep cool, including moving about during the night and living in a burrow during the day.

Concept

Desert animals have adapted to hot, dry conditions.

Objective

To explore ways desert animals keep cool

Content

Science, language arts

Background

Surface temperatures of desert soil can be extremely hot. Desert vegetation is sparse and cloud cover minimal. Thus, the sun shines unobstructed onto the soil. About half of the sun's heat is absorbed by the first few inches of soil and the other half is reflected back into the atmosphere. The temperature of the soil is also affected by dryness‹there is little water to evaporate and thus dissipate the heat.

While desert daytime temperatures may be high, nighttime temperatures may drop dramatically. Radiant heat from the sun rapidly warms the soil and air during the day, but then escapes without barriers into the atmosphere at night.

Desert animals have adapted to hot, dry conditions in a number of ways. Hot, exposed desert soils can be avoided by resting in the shade of a bush, on branches above ground, or in underground burrows. Moving about at night—being nocturnal—is another way to avoid the heat and conserve body fluids.

On the Web

A Field Guide page on the Kangaroo Rat.

Part A   Adaptations: no materials

Part B   Kangaroo Rat Burrow Box: half-gallon plastic or paper milk container (with top cut off), three thermometers, coarse-grain sand or dirt, sharp knife, goosenecked lamp with 60-watt bulb, paper, pencils

Part C   Night and Day: five or more high/low temperature readings from a desert area, graph paper, red and black markers

Part A   Adaptations (whole class)

• Discuss the need for animals to adapt to environmental conditions. What are the conditions of a desert environment during the day and night?
• What adaptations might animals have for living in hot places? What adaptations might animals have for living in dry places?

Part B   Kangaroo Rat Burrow Box (small groups)

• Mark the milk container 3 inches (7.5 cm) and 6 inches (15 cm) from the bottom. Cut a slit at each mark, large enough to insert a thermometer.
• Fill the container with sand.
• Position the lamp directly over the top of the sand. Record the temperature on all three thermometers.
• Turn the lamp on. Record the temperature at each level in 10 minutes, 20 minutes, and 30 minutes.
• Why would desert animals live in burrows?

Part C   Night and Day (individuals, small groups)

• Construct a graph showing temperature on the vertical axis and days on the horizontal axis.
• Using the high/low temperature readings from a desert area, plot low temperatures in black and connect the points.
• Plot the high temperatures with a red marker and connect the points.
• When is it cooler? How much cooler?
• Why are some desert animals nocturnal?

Local Connection
Graph high/low temperatures for your local area. If you live in a desert, use temperatures from a temperate area. Compare the difference between daytime and nighttime temperatures in a desert area with the difference between daytime and nighttime temperatures in a temperate area.

Key Words
adapted, nocturnal

Continue to Activity 8: The Water Storers: Cactus Adaptations