Camels: The Ship of the Desert
Camels are native to the deserts of Asia and North Africa. Two kinds of desert camels are dromedaries and Bactrians. Dromedaries have one hump and are best adapted for hot deserts. Bactrian camels, which have two humps, have adaptations for living in a cold desert. Most camels are domesticated, meaning they have been tamed so they can be used by humans. But a few Bactrian camels live in the wild in the remote grasslands of Mongolia, and some dromedaries that were taken to Australia now live wild in the outback. Domestic dromedaries are found mainly in the hot deserts of North Africa and Asia. Bactrian camels are mainly found in the cold, rocky Gobi desert in Asia.
Camels are the only animals that can carry heavy loads from place to place in the desert because they can go for long periods without eating or drinking water. A camel's hump doesn't carry water, as some believe. Instead the hump is filled with fat, which is a built-in food supply. This fat provides energy and water for the animal when food and water are scarce. When the fat is used up, the hump slumps over, but with rest and food the hump fills with fat and stands upright again.
Camels can go for weeks without a drink because they get some moisture from the food they eat and have stored as fat, and because their bodies have ways to prevent water loss. One physical adaptation a camel has for keeping water inside its body is a cavity in the camel's head. Dry air that the camel breathes in mixes with moisture in the cavity before moving through the camel's body, and moisture from the camel's breath is left in the cavity when the camel exhales. When thirsty camels do drink, they can gulp down large amounts. Some drink as much as 35 gallons (140 liters) of water at a time. Camels like clean water and may even turn down dirty water. So camels often get the first clean water drawn from a well while the thirsty people wait until the camels are finished before they drink.
A short thick layer of fur protects camels from high daytime temperatures and prevents heat from escaping quickly when temperatures drop at night. Bactrian camels live in areas that get very cold in the winter, and their thick, shaggy, winter coats keep them warm. These heavy coats are shed during the hot summer months so the camels do not overheat.
Other physical adaptations that allow camels to survive in the desert include long eyelashes to protect their eyes from sunlight and blowing sand. Their eyes also have an extra thin eyelid that the camel can see through. Their extra eyelids can be closed during a sandstorm to protect their eyes. Camels can also shut their nostrils to keep sand out of their noses, and they also have large padded hoofs that help them walk on the sand.
A camel's behavior also helps it survive in the desert. On extremely hot days, a camel stays as cool as possible by resting. A camel will lie down in any available shady place or directly face the sun so that only a small part of its body receives the sun's rays. Because their body temperatures may be lower than the air temperature, a group of camels may lie down with their bodies pressed together. Camels usually walk slowly, at a speed of about 3 miles per hour (5 km per hour), to keep from overheating. They walk by moving both legs on the same side together. This leg action produces a swaying, rocking motion much like that of a ship on water. Camels are sometimes called "ships of the desert."