Bactrian camels and dromedary or Arabian camels are large animals known for their humps, their amazing capacity to survive in extremely dry conditions, and their ability to transport people across arid deserts.
Bactrian camels probably originated in the cold deserts of the central Asian steppes, which are subject to great extremes of heat and cold. In contrast, the dromedary is native to the hot deserts of Africa and the Middle East. Consequently, while the two types of camel are similar in appearance, they exhibit physical differences related to their ability to survive in two very different environments.
The most obvious difference between the two types of camel is that the dromedary has one hump and the Bactrian has two. The camel stores fat in its hump, and sustains itself on the stored fat when there is no food available. As the dromedary uses up its store of fat, its hump shrinks, while the Bactrian’s hump merely flops to one side. The dromedary’s single hump, which is the only part of its body covered with thick fur, is believed to provide better protection from the sun than the Bactrian’s two humps, while the form and position of the Bactrian’s two humps provide better insulation against heat loss.
The bodies of Bactrians and dromedaries also differ in other ways. The Bactrian is shorter and stouter than the dromedary. A Bactrian measures about six feet (1.8 meters) at the shoulder, while the dromedary averages six and a half feet (two meters), and is generally of a much lighter build, with longer, thinner legs.
Bactrians have long, dark hair and grow a thick coat of insulating fur in the winter which they shed in the summer. Dromedaries, on the other hand, are better adapted to a hot climate because they have short, light hair over most of their body which allows their internal body heat to dissipate. Also, because they do not grow a winter coat they do not need to molt in the summer.
A less obvious difference is that dromedaries have calloused knees while Bactrians do not. When they rest, dromedaries keep their bodies away from the hot desert sand by leaning on their knees, and these callouses prevent their knees from being burnt.
Because they have shorter legs and a stouter build, Bactrian camels are well suited to maintaining their balance in mountainous terrain and on ice and snow. In contrast, long-legged dromedaries are better suited to walking on gently rolling sand dunes, and can travel much faster than Bactrians.
Both dromedaries and Bactrians are domesticated, and have traditionally been used in Asia and Africa for riding, as pack animals and for their milk, meat and hide or wool. A dromedary rider sits on top of that animal's single hump, while a Bactrian rider sits between the camel's two humps. A dromedary is better suited to riding or racing because of its lighter build, while the Bactrian’s heavier build makes it better suited for carrying heavy burdens. Bactrian camels are also reputed to have a gentler temperament than dromedaries. When they are excited or disturbed, dromedaries have a nasty habit of spitting cud, while Bactrians do not generally spit, although they may do so if they are abused.
Both dromedary and Bactrian milk is used for human consumption, and is considered more nutritious than cow’s milk. However, while a Bactrian produces an average of five liters a day, a dromedary is much more productive, and can produce up to 20 liters a day.