Camels are among the largest desert animals, but they are so well adapted to dry conditions that they have been domesticated for thousands of years by people living in desert areas. They are kept mainly as beasts of burden but are also eaten and used as racing animals! Camels’ feet are able to splay out to prevent them from sinking into loose sand. They are able to close their nostrils to keep out sand, and their eyes are also protected by long eyelashes. The fat in their humps is a food store. Camels very rarely sweat, so they are able to conserve the water in their bodies much more efficiently than human beings.
Desert adapted camels have evolved physiological adaptations that reduce the amount of water lost or are able to tolerate significant amounts of water loss [9]. Where green forage is available in mild climates, the camel may go several months without drinking. During the winter and cold seasons of the year camels can go without water for months. They do not even drink when offered water. Under very hot conditions, it may drink only every eight to ten days and lose up to 30 percent of its body weight through dehydration. When the mean temperature reach 30-35°C, camels can go 10-15 days without water but when the temperature exceeds 40°C, shorter periods between watering is necessary.
The digestive and urinary tracts are well specialized in water conservation. Cattle lose 20 to 40 liters of fluid daily through feces, whereas camels lose only 1.3 liters. This is one of the primary methods for resisting water deprivation in the desert. Fluid is absorbed in the end part of the intestines, where the small fecal balls are produced.
The rumen helps maintain water balance in two ways. First, the rumen of hydrated ungulates and the foregut of camels contain a large volume of water, approximately equal to 20% of body weight, and may buffer ungulates against short term water deprivation. During the first few days of dehydration, fluid contained in the rumen is used to maintain water balance of blood and body tissues and represents a large portion (50–70%) of the water lost during dehydration. Second, after dehydration in some species, the rumen plays a role in the prevention of hemolysis and osmotic tissue shock during rapid rehydration.
The kidney is an important organ involved in the removal of unwanted nitrogenous substances, excess water and relative maintenance of osmotic concentration of the blood. The camel’s kidneys play a major role in the process of conserving water through increasing the osmolality of urine. The kidney is characterized by a long loop of henle, and a well-developed medulla. During dehydration, the kidneys reduce water losses both by decreasing the glomerular filtration rate and by increasing the tubular re-absorption of water.
The long loops of henle, which are four to six times longer than in cattle, have the function of both concentrating urine and reducing its flow. A dehydrated camel urinates only drops of concentrated urine being shown by white stripes of salt crystals on the hind legs and tail. This concentrated urine not only serves to conserve water, but also allows camels to drink water which is more concentrated than sea water (above 3% NaCl), and to eat salty plants (halophytes) that would otherwise be toxic. Anti-diuretic hormone (ADH) is important in regulating the volume of urine excreted and its concentration. ADH is produced in the hypothalamus and is released into the blood stream in response to increased blood osmolarity. Larger release of ADH leads to a fast renal response that causes increased re-absorption of water. This leads to a smaller volume of more concentrated urine being excreted.
The body of camels can tolerate loss of water over 30% of body weight whereas most mammals die if they lose half of this value. Rehydration following a period of water deprivation is important for animal survival. A camel may drink more than one third of its body weight as it rehydrates. In terms of actual water intake reported 110 liters in 10 minutes. In other animals rehydration at these levels would lead to over hydration and possibly death. The camel is able to do this as large amounts of water can be stored for up to 24 hours in the gut to avoid a rapid dilution of the blood.
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