Camels: Evolution, Migration, and Physiology

Domesticated thousands of years ago by frankincense traders, who trained the gangly cud-chewer to make the long and arduous journey from southern Arabia to the northern regions of the Middle East, the camel went on to become the desert dweller's primary source of transport, shade, milk, meat, wool and hides.

Scientists believe that ancestors of the modern camel lived in North America at least 40 million years ago.  Although the ancestors of the lamas and camels appear to have diverged sometime in the Eocene epoch, they weren't completely separated from each other until the Pleistocene, when the ancestors of the camels migrated across the Bering Strait (temporary) land bridge to Asia.  Lamas migrated to South American, and all camel died out in North America.  Once in Asia, camels migrated through eastern Europe, the Middle East and North Africa.

In Asia, two groups separated to become the two chief types of camel known today: the one-humped or dromedary and the two-humped, shorter-legged Bactrian camel.  It is thought that the dromedary may have evolved from the Bactrian camel.  However the hump(s) may have been acquired as a result of domestication.  The one-humped camel (Camelus dromedarius ) is found in the Arabian deserts, while the two-humped camel (Camelus bactrianus ) is an Asiatic animal.

All camels are similar, in having 37 pairs of chromosomes.  The Old World camels may be crossed, producing fertile offspring. (New World camels can be crossed to each other with similar results.)  Despite some major differences in size, all of the camels are basically similar in structure.  Because camels evolved in a semi-desert environment, they have developed sophisticated physiological adaptations for coping with both heat and dehydration.

All camels have a complex, 3-compartmented stomach.  Although they are not considered ruminants, they do regurgitate and rechew ingested forage.  In fact, they are more efficient at feed conversion than are ruminants in extracting protein and energy from poor quality forages.

Wild camels became extinct in North Africa before historic times (3000 B.C.), leaving only the domesticated stock.  However, in the case of the Bactrian camel, there are a small number of animals (300 to 700) located in a small area in the Trans-Altai Gobi Desert, that are considered a wild population.

 

Dromedaries (Arabian, One-Humped Camel):

The Bedouin name for Camelus dromedarius, is the "one-hump" dromedary, also known as the Arabian camel.  These camels were domesticated even earlier than the Bactrians (two-humped, Asian camels), before 3000 B.C. in the Arabian peninsula.  The term "dromedary" is derived from the dromos (Greek for "road") and thus is directly applicable only to the racing or riding dromedary.  However, the term is used throughout the world to describe this species.  Dromedaries were first associated with nomadic Semitic cultures and did not become important until the rise of the Arabian culture.  They became important domestic animals only with the Moslem conquests of Egypt in the 7th to 11th centuries A.D.

 Dromedary's adaptation to heat and dehydration:

The dromedary camel does not store water any more than does any other species, yet it does not need to drink water for days.  It can handle extreme dehydration as a result of a number of different physiological adaptations.  Camels have been known to lose safely body water equivalent to 40% of its body weight, a loss that would be lethal in any other animal.  How do they do this?

·        Plasma volume is maintained at the expense of tissue fluid, so that circulation is not impaired.

·        The small oval erythrocyte of the camel can continue to circulate in situations of increased blood viscosity.

·        Camels can take in a very large amount of water at one session to make up for previous fluid loss.  In other animals, this would result in severe osmotic problems.  Camels can do this because water is absorbed very slowly from their stomach and intestines, allowing time for equilibration.  Furthermore, their erythrocytes can swell to 240% of normal size without bursting. (Other species can only go to 150%.)

·        Their kidneys are capable of concentrating their urine markedly to reduce water loss.  The urine can become as thick as syrup and have twice the salt content of sea water.

·        They can extract water from their fecal pellets so much that these can be used immediately for fuel upon voiding.

·        A further adaptation solely for heat is involved in the camel's ability to have a large fluctuation in body temperature (from 97.7 to 107.6 degrees F).  During the day, its body acts as a heat sink, and during the cool night of the desert, excess body heat is dissipated by conduction.

 Contribution of the Camel:

In technologically-advanced Saudi Arabia, even the Bedouin are not as dependent on the camel as they once were.  These days, camels are valued more as thoroughbred racing animals and sentimental images of the past than as the mainstay of transportation.  But in many parts of Africa and Asia today, camels still pull ploughs, turn waterwheels and transport people and goods to market along desert routes impassable by wheeled vehicles.

Camels are also raised for its meat and its milk.  The best camel meat comes from young male camels.  It is regarded as a delicacy in the Arabian diet, and is gaining popularity in arid lands where it is difficult to herd sheep, cattle and goats.  Although it makes for tough chewing, the taste is not unlike beef.

Camel's milk is much more nutritious than that from a cow.  It is lower in fat and lactose, and higher in potassium, iron and Vitamin C.  It is normally drunk fresh, and the warm frothy liquid, heavy and sweet, is usually an acquired taste for the Western palate.  Most Saudi Arabian camels are females reared for their milk in dairy herds.

To appreciate the unique contribution that the Arabian camel has made to the people and history of desert lands, here's a comprehensive fact-pack on the special characteristics, body structure and behavior patterns of this amazing creature.

 Body Structure and Behavioral Patterns:

Body Structure:  A fully-grown adult camel stands 1.85m/6 feet at the shoulder and 2.15m/7 feet at the hump.  A fully-grown camel can weigh up to 700kg/1542lbs.  A camel's long, thin legs have powerful muscles which allow the animal to carry heavy loads over long distances.  A camel can carry as much as 450kg/990lbs, but a usual and more comfortable cargo weight is 150kgs/330lbs.  It is usual for a camel to work as a beast of burden for only six to eight months of the year; the remainder of the time it needs to rest and recuperate.

Camels come in every shade of brown, from cream to almost black. A camel's ears are small, but its hearing is acute—even if, like the donkey or basset hound, it chooses to pay no attention when given a command!  A camel's ears are lined with fur to filter out sand and dust blowing into the ear canal.

A camel's eyes are large, with a soft, doe-like expression.  They are protected by a double row of long curly eyelashes that also help keep out sand and dust, while thick bushy eyebrows shield the eyes from the desert sun.

A camel's rope-like tail is over 50cm/19" long.

Camels have broad, flat, leathery pads with two toes on each foot.  When the camel places its foot on the ground the pads spread, preventing the foot from sinking into the sand.  When walking, the camel moves both feet on one side of its body, then both feet on the other.  This gait suggests the rolling motion of a boat, explaining the camel's "ship of the desert" nickname.

The camel has a large mouth, with 34 sharp teeth. They enable the animal to eat rough thorny bushes without damaging the lining of its mouth, and can be used as biting weapons against predators if need be. A camel gulps down its food without chewing it first, later regurgitating the undigested food and chewing it in cud form.

A camel's nasal passages are protected by large muscular nostrils that can be opened and closed at will. When a camel twitches its nose, it is cooling the incoming air and condensing moisture from its outgoing breath.

Thick callus-like bare spots of dry skin appear on a camel's chest and knee joints when the animal reaches five months of age.  These leathery patches help support the animal's body weight when kneeling, resting and rising.

Behavioral Patterns:  Unpredictable at best, camels have the reputation of being bad-tempered and obstinate creatures who spit and kick.  In reality, they tend to be good-tempered, patient and intelligent.  The moaning and bawling sound they make when they're loaded up and have to rise to their feet is like the grunting and heavy breathing of a weight-lifter in action, not a sign of displeasure at having to do some work.

Camels do not pant, and they perspire very little.  Humans start to sweat when the outside temperature rises above the normal body temperature of 37° C, but the camel has a unique body thermostat.  It can raise its body temperature tolerance level as much as 6°C before perspiring, thereby conserving body fluids and avoiding unnecessary water loss.  No other mammal can do this.  Because the camel's body temperature is often lower than air temperature, a group of resting camels will even avoid excessive heat by pressing against each other.

A camel can go 5 to 7 days with little or no food and water, and can lose a quarter of its body weight without impairing its normal functions.  These days, camels rely on man for their preferred food of dates, grass and grains such as wheat and oats, but a working camel travelling across an area where food is scarce can easily survive on thorny scrub or whatever it can find—bones, seeds, dried leaves, or even its owner's tent!

Contrary to popular belief, a camel does not store water in its hump.  It is in fact a mound of fatty tissue from which the animal draws energy when food is hard to find.  When a camel uses its hump fat for sustenance, the mound becomes flabby and shrinks.  If a camel draws too much fat, the small remaining lump will flop from it's upright position and hang down the camel's side.  Food and a few days' rest will return the hump to its normal firm condition.

Normal 'amble speed' for a walking camel is 5kph/3mph; a working camel will typically cover 40km/25 miles a day.  Racing camels can reach 20kph/12mph at the gallop.

All camels molt in spring and have grown a new coat by autumn.  Camel hair is sought after world-wide for high-quality coats, garments and artists' brushes, as well as being used to make traditional Bedouin rugs and tents.  A camel can shed as much as 2.25 kilos/5 lbs of hair at each molt.

After a gestation periods of 13 months, a camel cow usually bears a single calf, and occasionally twins.  The calves walk within hours of birth, but remain close to their mothers until they reach maturity at five years of age.  The normal life span of a camel is 40 years, although a working camel retires from active duty at 25.

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Bactrian Camels (Asian, Two-Humped Camel):

Length: 7 to 11 feet
Height: 6 to 8 feet
Weight: 1000 to 1500 pounds
Number of young: 1
Home: Mongolia

 

Two closely related types of camel are sometimes confused: the Arabian (or dromedary) camel with 1 hump and the Bactrian camel with 2 humps.  The Bactrian camel is also heavier and has a longer coat.  While Arabian camels are now all domesticated, some Bactrian camels still live in the wild in the Gobi desert, between southwest Mongolia and northwest China.  These wild camels were widespread until 1920.  Now they are endangered.

Bactrian camels are thought to have been domesticated prior to 2500 B.C. (The name is derived from a place name, Baktria, on the Oxus River in northern Afghanistan.  This seems strange, since the domesticated form of this camel didn't originate there, nor is it found there currently.)

Domesticated Bactrian camels were found in southern Russia by 1700 to 1200 B.C. and even in western Siberia by the 10th century B.C.  They were used in China as early as 300 B.C. as the original "silk route" camels, but were replaced by crossbreeds of the Bactrian/dromedary later on.

Two thousand years ago, travelers rode on Bactrian camels and used them to carry good and supplies across the plains of Asia.  This camel can carry a load of more than 450 pounds.  It can travel 20 to 25 mile a day on high, dry plateaus, climbing along mountaintops more than 10,000 feet high.

A Bactrian camel can outrace a horse over long distances.  The camel can run for several hours without stopping.  In the summer, it can easily survive for 2 or 3 days without food and water.  In winter, it can live without food and water for up to a week.

In the wild, the Bactrian camel lives in small groups that look for grazing grounds in the desert of Central Asia.  Grasses, leaves, and bushes make up its daily food.  The mating season begins in February.  The female carries the single young for 13 months, and the baby camel is born in March of the following year.

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Copyright © 2011 by Marisa Montes. All rights reserved.
Revised: 11 Nov 2011 13:05:00 -0500 .