Camels are desert inhabitants, recognized by their distinctive back structures. They have long captured human curiosity, especially regarding the number of these features. The number of these formations defines species, hinting at diverse evolutionary paths. This variation reveals much about their biology and desert adaptations.
Distinct Camel Species
Hump count distinguishes the two main camel species. The one-humped Camelus dromedarius is known as the dromedary or Arabian camel. The two-humped Camelus bactrianus is the Bactrian camel. A third, critically endangered wild Bactrian camel (Camelus ferus), also has two humps.
Dromedaries are taller and lighter, weighing 300-600 kg and standing 1.8-2 meters at the shoulder. Their single hump is prominent and rounded. Bactrians are stockier, weighing 450-700 kg, with a denser, shaggier coat in colder seasons. Both have long legs, but the Bactrian’s robust build helps it endure extreme cold.
The Purpose of the Hump(s)
Camel humps do not store water; they are reservoirs of fatty tissue. A hump can store up to 36 kilograms of fat. This fat provides energy, allowing camels to survive extended periods without food in arid habitats.
When food is scarce, the camel metabolizes hump fat for energy and metabolic water. This efficient process provides sustenance for long journeys across harsh environments. As fat reserves are used, the hump diminishes, becoming limp. With sufficient food, it regains its plump, erect appearance. Storing fat centrally, rather than distributing it, also aids thermoregulation by allowing the body to dissipate heat effectively.
Adaptations Beyond the Hump
Camels have adaptations beyond their humps for survival in extreme desert conditions. Their wide, padded feet with two toes distribute weight, preventing sinking into soft sand and protecting from scorching ground temperatures, allowing easy traversal of sandy terrains.
For sand and dust protection, camels have three eyelids, two rows of long eyelashes, and nostrils that close completely to form a slit. Camels regulate body temperature, allowing it to fluctuate significantly (up to 42°C or 106°F) before sweating, conserving water. They also produce concentrated urine and dry feces, minimizing water loss.
Geographic Distribution and Habitat
Camel species are found worldwide, each suited to its environment. Dromedary camels (Camelus dromedarius) are found in hot deserts of North Africa, the Middle East, and India. Their single hump and lighter build adapt them to hot, arid, sandy climates.
Bactrian camels (Camelus bactrianus) inhabit colder, mountainous, and snowy deserts of Central Asia, including Mongolia and China. Their two humps and thick, shaggy coats insulate against extreme cold, where temperatures drop significantly below freezing. These adaptations reflect evolutionary pressures that shaped each species to thrive in challenging desert ecosystems.