A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the Bactrian camel has two humps. They are native to the dry desert areas of West Asia, and Central and East Asia, respectively. Both species are domesticated to provide milk and meat, and as beasts of burden.
The term camel, (from the Arabic جمل, ǧʿl, derived from the triconsonantal root signifying "beauty"), is also used more broadly to describe any of the six camel-like creatures in the family Camelidae: the two true camels, and the four South American camelids, the llama, alpaca, guanaco, and vicuña.
The average life expectancy of a camel is 40 to 50 years. A fully grown adult camel stands 1.85 m (6 ft 1 in) at the shoulder and 2.15 m (7 ft 1 in) at the hump. The hump rises about 30 inches (76.20 cm) out of its body. Camels can run at up to 65 km/h (40 mph) in short bursts and sustain speeds of up to 40 km/h (25 mph).
Fossil evidence indicates that the ancestors of modern camels evolved in North America during the Palaeogene period (see also Camelops), and later spread to most parts of Asia. Humans first domesticated camels well before 2000 BC.
Distribution and numbersEdit
The almost 14 million dromedaries alive today are domesticated animals (mostly living in Somalia, the Sahel, Maghreb, Middle East and Indian subcontinent). An estimated quarter of the world's camel population is found in Somalia and in the Somali Region of Ethiopia, where the camel is an important part of nomadic Somali life. They provide the Somali people with milk, food and transportation.
The Bactrian camel is now reduced to an estimated 1.4 million animals, mostly domesticated. It is thought that there are about 1000 wild Bactrian camels in the Gobi Desert in China and Mongolia.
There is a substantial feral population of dromedaries estimated at up to 1,000,000 in central parts of Australia, descended from individuals introduced as transport animals in the 19th century and early 20th century. This population is growing at approximately 18% per year. The government of South Australia has decided to cull the animals using aerial marksmen, because the camels use too much of the limited resources needed by sheep farmers. For more information, see Australian feral camel.
A small population of introduced camels, dromedaries and Bactrians survived in the Southwest United States until the second half of the 20th Century. These animals, imported from Turkey, were part of the U.S. Camel Corps experiment and used as draft animals in mines and escaped or were released after the project was terminated. A descendant of one of these was seen by a backpacker in Los Padres National Forest in 1972. Twenty-three Bactrian camels were brought to Canada during the Cariboo Gold Rush.
Camels do not store water in their humps as is commonly believed. The humps are actually a reservoir of fatty tissue. Concentrating body fat in their humps minimizes heat-trapping insulation throughout the rest of their body, which may be an adaptation to living in hot climates. When this tissue is metabolized, it acts as a source of energy, and yields more than 1 g of water for each 1 g of fat converted through reaction with oxygen from air. This process of fat metabolization generates a net loss of water through respiration for the oxygen required to convert the fat.
Their ability to withstand long periods without water is due to a series of physiological adaptations. Their red blood cells have an oval shape, unlike those of other mammals, which are circular. This is to facilitate their flow in a dehydrated state. These cells are also more stable in order to withstand high osmotic variation without rupturing when drinking large amounts of water (100 litres (22 imp gal; 26 US gal) to 150 litres (33 imp gal; 40 US gal) in one drink). Oval red corpuscles are not found in any other mammal, but are present in reptiles, birds, and fish.
Camels are able to withstand changes in body temperature and water content that would kill most other animals. Their temperature ranges from 34 °C (93 °F) at night and up to 41 °C (106 °F) during the day, and only above this threshold will they begin to sweat. The upper body temperature range is often not reached during the day in milder climatic conditions, and therefore, the camel may not sweat at all during the day. Evaporation of their sweat takes place at the skin level, not at the surface of their coat, thereby being very efficient at cooling the body compared to the amount of water lost through perspiration.
A feature of their nostrils is that a large amount of water vapor in their exhalations is trapped and returned to their body fluids, thereby reducing the amount of water lost through respiration. They can withstand at least 20-25% weight loss due to sweating (most mammals can only withstand about 15% dehydration before cardiac failure results from circulatory disturbance). A camel's blood remains hydrated, even though the body fluids are lost, until this 25% limit is reached.
Camels eating green herbage can ingest sufficient moisture in milder conditions to maintain their bodies' hydrated state without the need for drinking.
A camel's thick coat reflects sunlight, and also insulates it from the intense heat radiated from desert sand. A shorn camel has to sweat 50% more to avoid overheating. Their long legs help by keeping them further from the hot ground. Camels have been known to swim.
Their mouth is very sturdy, able to chew thorny desert plants. Long eyelashes and ear hairs, together with sealable nostrils, form a barrier against sand. Their gait and their widened feet help them move without sinking into the sand.
The kidneys and intestines of a camel are very efficient at retaining water. Urine comes out as a thick syrup, and their feces is so dry that they can fuel fires.
All camelids have an unusual immune system. In all mammals, the Y-shaped antibody molecules consist of two heavy (or long) chains along the length of the Y, and two light (or short) chains at each tip of the Y. Camels also have antibody molecules that have only two heavy chains, which makes them smaller and more durable. These heavy chain-only antibodies, which were discovered in 1993, probably developed 50 million years ago, after camelids split from ruminants and pigs, according to biochemist Serge Muyldermans.
The camel is the only animal to have replaced the wheel (mainly in North Africa) where the wheel had already been established. The camel did not lose that distinction until the wheel was combined with the internal combustion engine in the 20th century.