The dromedary camel is incredibly well-adapted to hot, arid climates. The camel can go days without drinking water, surviving extreme dehydration and safely losing 40% of its body weight in water. This ability is, in part, due to uniquely oval red blood cells (which carry oxygen). The long axis of these oval cells is oriented with the flow of blood, enabling the cells to cross over the smallest of blood vessels, even when blood thickens during times of dehydration.
Additionally, the camel’s red blood cells are capable of expanding up to 240% of their original volume without rupturing; most animals’ cells can expand only 150%. This makes it possible for the camel to drink the necessarily large amount of water to recover from dehydration.
“Camelid erythrocytes are small…and elipsoid18,19,56,58 and circulate in larger numbers than in other mammalian species. The small size and shape result in a lower packed cell volume (PCV). Camelid erythrocytes are oriented with the long axis in the direction of the blood flow; this makes it possible to traverse small capillaries, resulting in fewer problems of sludging when the viscosity of the blood increases during dehydration.” (Fowler 2010:407,411)
“Even after severe dehydration, the camel is able to drink sufficient water at one session to make up the deficit. This amount of water would cause severe osmotic problems in humans or other animals. In the camel, water is absorbed from the stomach and intestines slowly, allowing equilibrium to be established. The erythrocytes are able to avoid osmotic problems by swelling to 240% of their initial volume without rupturing… In other species, erythrocytes can swell only to 150%…” (Fowler 2010:28)