When the rabbit becomes hot, blood vessels in the ears dilate, causing heat in its body to radiate back into the air. The jackrabbit is a good example of both behavioral and physiological adaptations. The kangaroo rat lives its entire life eating only dry plant food and never drinks water. Its body produces water by metabolizing the dry food it eats. Active only at night, the kangaroo rat spends the day sleeping in its cool burrow underground, plugging the opening with dirt, keeping the heat out and moisture in.
Some large animals are more dependent on water and rely on their mobility to reach water sources.
Bighorn sheep and mule deer, for example, must have free water. Their powerful bodies provide the energy to transport them many miles to the river, a rain-filled pothole or a spring. In addition, a considerable amount of water is derived from the plant food they eat, so bighorn and deer are able to go several days in between drinks. Carnivores like the coyote, bobcat, mountain lion and birds of prey rely heavily on the fluids found within the animals they eat to supplement the water they drink. Fur and feathers can play a double role in some animals by shielding them from the sun during the day and insulating them from the cold at night.