The camel is a large, humpbacked mammal, and the first animal domesticated by man in prehistoric times.
Two species are recognized: the heavily built, two-humped Bactrian camel, which inhabits the deserts of central Asia, and the single-humped Arabian camel, or dromedary, which is widespread through.out the Middle East, India, and North Africa. Neither species has been much modified by man. The Bactrian camel, living in regions where the winters are very cold, has a longer, darker winter coat, and its legs are shorter.
An adult Bactrian seldom measures more than 7 feet from the ground to the top of the humps-about the height of the shoulder in the taller and more slender dromedary.
Camels have even-toed, digitigrade feet (that is, the posterior of the foot is raised and it walks on its digits). The third and fourth toes are united by thick, fleshy pads and tipped with nail-like hooves. Horny pads on the chest and knees support the body when the camel kneels; these pads are present in the newborn calf. The limbs and neck of the camel are elongated, the upper lip is cleft, and the ears are small.
The hump of the camel is a food store which, because it is concentrated in one large deposit and not distributed as a subcutaneous layer of fat, allows the rest of the body to lose heat more rapidly, The notion that the camel stores water in its hump, or that the fat of which the hump is composed is itself a water store, is erroneous. On oxidation the fat does produce metabolic water, but the extra oxygen used in the process involves in turn an extra loss of water through the lungs, just about canceling any water gain from oxidation.
The camel is a very phlegmatic animal and has a reputation for stupidity and obstinacy. The males are quarrelsome during the rutting season and bite savagely when they fight.
The dromedary has a pronounced rutting season at the time of the rains in winter; pregnancy is prolonged for nearly a year until the following rainfall. The Bactrian has an even longer gestation period of 370 to 440 days. In both species the young are born singly and suckled for three or four months, and the interval between births is two years. Camels are full- grown at 16 or 17 years; the normal life span is about 25 years.
Droves of wild Bactrian camels in the Gobi desert consist of one or two males and three to five females. They sleep at night in open spaces and graze during the day on grasses, brushwood, and scrub, migrating to the northern part of the range in spring and returning southward in autumn.
Camels mate in January and February.
When moving fast, camels pace. That is, they raise both legs on the same side of the body and advance them simultaneously. A speed of about 6 mph may be achieved, but it cannot be maintained for more than a few hours. The normal walking speed of a fast dromedary used for racing by Bedouins is 3.5 mph, and its maximum speed is approximately 10 mph. A camel cannot gallop for more than a few yards, however. In order to keep a racing camel at its fastest pace-the long trot- the rider must cultivate a rankling sore on its neck and prick it constantly.
Members of the suborder Tylopoda (which includes llamas, camels and dromedaries) have only two functional toes on each foot.
The members of the genus Camelus have on their backs humps of fatty tissues which contain stored food.
The Bactrian camel, Camelus bactrianus, has two humps. It is almost 2 meters high at the shoulders and is heavier and stronger than the dromedary.
The Bactrian camel is found throughout Central Asia from China to Turkestan and, apart from a few wild herds in the Gobi Desert, is known in only a domesticated state. It is used for transport and also provides milk, meat, leather and hair for spinning and weaving.
The dromedary, Camelus dromedarius, also known as the Arabian camel, has only one hump. It is well adapted to a desert environment, with broad feet for walking in sand and long eyelashes and nostrils that close for protection against dust.
Like the Bactrian camel, the dromedary can feed on coarse desert plants and is able to survive for long periods without water, mainly through the variability of its body temperature. When the outside temperature rises, most mammals keep their body temperature stable by perspiration and thereby lose a lot of water. However, the camel’s body temperature may rise by 6 degrees Celsius before the animal begins to perspire without becoming feverish.
When the heat of the day is greatest, camels sit facing the Sun and close to one another, thus exposing smaller areas of their bodies to the Sun’s heat.
The mares separate from the main herd to give birth to a foal every second year. The gestation period is 12 to 13 months and, within 2 days of its being born, the foal is running with ease and keeping up with the herd as it moves on.
Although they chew the cud, camels differ from most true ruminants in that the adults retain two incisor teeth in the upper jaw.
They also differ in the lack of an omasum, or third section, to their stomach. The smooth-walled rumen, or anterior section of the stomach, has diverticula (small sacs) opening out from it. The diverticula were formerly called “water sacs” because of a now-discarded theory (which appeared in Pliny’s Natural History) that the camel stores water in them. Actually, the fluid in these glandular sacs has the same salt content as the rest of the body, looks like green pea soup, and is quite repulsive.
To the desert traveler without water, however, any fluid seems attractive, and it is quite possible that the many tales of people who have saved their lives by killing their camels to drink this fluid are true. Other internal differences of the camel include the absence of a gall bladder and the presence of oval red blood corpuscles, which are not found in other mammals.
By Matson Collection [Public domain or Public domain], via Wikimedia Commons
Besides the heavy eyelids and lashes and the slit nostrils that protect it against desert winds, a camel’s body exhibits many special adaptations to life in hot, dry regions. Thus, camels have unusually low metabolic rates. They can exist on dry food for two weeks or more, depending on the temperature, because they tolerate a much greater depletion in body water than most other mammals.
A camel may lose about 30% of its weight in body water without ill effects, as compared to about 12% in man. During periods of desiccation the blood of most mammals becomes increasingly viscous; it therefore circulates more and more slowly, until it cannot carry away metabolic body heat to the skin quickly enough, leading to “explosive heat death”. This is avoided in camels by a physiological mechanism that ensures that water is lost from the body tissues alone, while the blood’s water content remains fairly constant.
The camel does not lose its appetite during periods of desiccation, and can graze over a wide area away from water. When presented with water after a moderate dry period, it takes in, at one time, as much water as was lost-a camel can drink 25 gallons (100 liters) or more in a very short time. The body fluids rapidly become diluted to an extent that could not be tolerated by other mammals, which would die from water intoxication even if they took in a much smaller amount.
Because of its ability to lose water from body tissues alone, and because of its relatively small surface area, the camel can afford to sweat. The coarse hair on the back is well ventilated, allowing the evaporation of sweat to occur on the skin and provide maximum cooling. (The hair also acts as a barrier to the sun’s radiation and slows the conduction of heat from the environment.)
Undue water loss from sweating is avoided because the camel’s temperature can vary over a range greater than that of other mammals. In the North African summer a camel may have a morning temperature of 93°F, and an afternoon maximum of 105°F. Sweating does not commence until the higher temperature is reached; therefore the camel is able to store heat during the day, which can be lost at night without expense of water.
The rate of urine flow is low in camels, and little water is lost with the feces. Moreover, investigations of kidney function in the camel have revealed an extremely low secretion of urea when its food is low in protein. The camel, like most ruminants, can utilize urea for microbial synthesis of protein-a valuable asset to animals that have to exist on low-grade diets in deserts.
Thus, the adaptations of the camel to its hot environment do not involve independence from drinking water but the ability to economize the water available and to tolerate wider variations in body temperature and water content. In winter, when the temperature is comparatively low and water is not needed for heat regulation, camels become independent of drinking water for periods of several months.