Old World Camels
The Bactrian, or two-humped, camel (Camelus ferus) is the largest species, native to the rocky deserts in Asia. These wild camels were the ancestors of the domestic Bactrian camel, C. bactrianus. These animals are named for the Baktria region of ancient Persia (now Iran), and can withstand severe cold as well as extreme heat (up to 122°F [50°C]. Bactrian camels have a thick and shaggy coat, with very long hair growing downward from their necks. Domesticated bactrians have longer hair than the wild species.
The Bactrian camel stands about 6.5 ft (2 m) high at the shoulder and weighs up to 1,500 lb (680 kg) and can run up to 40 mph (65 kph). Bactrian camels can carry loads of up to 1,000 lb (454 kg), about twice as much as a dromedary can carry. Although Bactrian camels breed well in zoos, they are almost extinct in the wild, with probably only a few hundred left in the Gobi Desert of Asia.
The most common camel is the one-humped Arabian, or dromedary camel, which is known today only as a domesticated species, C. dromedarius. Although the name "dromedary" has now been given to all onehumped camels, it originated with a special breed developed for great speed in racing. Racing camels can also run over great distances—covering more than 100 mi (160 km) in a day.
Dromedary camels are taller but lighter than Bactrian camels, reaching 7 ft (2.1 m) at the shoulder, and an average weight of about 1,200 lb (550 kg). The animals' hair can vary in color from dark brown to white, though most are the tan color referred to as "camel's hair." The Arabian camel has long been extinct in the wild, though feral populations (domestic animals living in the wild) occur in various parts of the world, including central Australia where the herds number up to 50,000.
Although one-humped and two-humped camels are given separate species names, they can interbreed fairly easily and are probably varieties of a single species. The product of interbreeding, called a tulu, usually has two humps. This is not surprising in view of the fact that the one-humped camel actually has another hump that lies unnoticeably in the shoulder region.
Both species are used primarily as pack animals in desert countries, where they travel at a leisurely pace of about 25 mi (40 km) a day, carrying both goods and people, mounted in saddles that fit over the single hump or between the two humps. A camel's hump contains 80 lb (36 kg) of fat, not water, which provides the animal with energy when no food is available. The hump shrinks and becomes flabby as the fat supply is used up, but it firms up again when the animal eats plants and drinks water. A camel can go for a week and even travel 100 mi (160 km) or more in a desert summer without drinking. Camels can withstand a great deal of dehydration and can lose more than 40% of their body weight without harm. In winter, camels can go for many weeks without drinking. When dehydrated camels do reach water, they make up for any previous lack by drinking as much as possible very quickly. They have been known to drink as much as 30-40 gal (114-150 l) in a single session to rehydrate.
Other adaptations of camels for dealing with desert conditions include a reduced number of sweat glands which only function in extreme heat or exertion. At heat stresses that would cause most animals to sweat to cool their bodies, and thus use up water, the camel's body temperature can temporarily rise several degrees, a strategy known as heat storage. The thick coat on the back of the camel prevents heat from the sun from being absorbed. The hoofed feet have broad, thick pads that provide a solid base on shifting sands. The thick, bushy eyebrows and double rows of eyelashes keep sand out of their eyes. Any sand that does enter the eye is dislodged by a transparent third eyelid that slides across the eye. Hair inside a camel's ears prevents sand from easily blowing in the ear canal. In addition, camels can voluntarily squeeze shut both their slit-like nostrils and their mouth to prevent sand from entering. The camel's mouth has a thick, leathery lining that prevents the thorny desert plants from damaging the mouth. The round, leathery kneepads of camels protect their knees when they kneel on the hot sand or on hard rocky ground.
Camels are central to the survival and culture of the nomadic peoples of the old world deserts. Camel hair, shed in large clumps, is woven into clothing and tents, while camel milk and meat provide nourishment, particularly on special occasions. Nomadic people often let their camels loose in the desert for several months at a time, which includes the mating season. Camels have a gestation period of about 14 months, after which the mother camel gives birth to a single 80 lb (36 kg) offspring, every other year. The long-legged calves, become independent at about four years, and domesticated camels can live up to about 50 years.