Arabian camels can carry loads of 400 to 600 pounds across the desert, and bactrians can carry up to 800 pounds. Caravans consisting of 50 or more camels tied head to tail and led by an unburdened donkey usually travel at a rate of 2 to 4 miles (3.2 to 6.4 km) per hour, stopping to rest at waterholes.
Because of their height, camels must usually kneel to be loaded or mounted. Unlike many domestic animals, camels resist being loaded by snapping, hissing, kicking, swaying from side to side to shake off the load, spitting, bleating, whining, and sobbing. Once loaded, however, most camels bear their burden dutifully, without causing any disturbance.
Since World War II and the introduction of motor trucks, the use of camels as beasts of burden has declined rapidly. Camels are now valuable chiefly for the products they yield. Camel meat and milk are important foods in North Africa and in Asia. Camel hide is used to make sandals, jugs, and other containers, while the hair is used in rugs, tents, and clothing. The dried bones are often used in decorative art as a substitute for ivory, and the dung is used as fuel.
Camels are usually bred during the damp seasons. The females generally bear only one colt, or calf, at a time. Arabian camels deliver about 315 days after mating, and bactrians give birth in about 385 days. Colts weigh about 30 pounds (13 kg) at birth and are born with their eyes wide open and with a coat of hair. The young mature in about 5 years and may live up to 40 years.