Camels do not store water in
their humps as is commonly believed. The humps are actually a
reservoir of fatty tissue. Concentrating body fat in their humps
minimizes heat-trapping insulation throughout the rest of their
body, which may be an adaptation to living in hot climates. When
this tissue is metabolized, it acts as a source of energy, and
yields more than 1 g of water for each 1 g of fat converted
through reaction with oxygen from air. This process of fat
metabolization generates a net loss of water through respiration
for the oxygen required to convert the fat.
Their ability to withstand
long periods without water is due to a series of physiological
adaptations. Their red blood cells have an oval shape, unlike
those of other mammals, which are circular. This facilitates
their flow in a dehydrated state. These cells are also more
stable in order to withstand high osmotic variation without
rupturing when drinking large amounts of water (100 litres (22
imp gal; 26 US gal) to 150 litres (33 imp gal; 40 US gal) in one
drink. Oval red corpuscles are not found in any other mammal,
but are present in reptiles, birds and fish.
Commercial camel market
headcount in 2003
Camels are able to withstand
changes in body temperature and water consumption that would
kill most other animals. Their temperature ranges from 34
°C (93 °F) at night and up to 41 °C (106 °F) during the day, and
only above this threshold will they begin to sweat. The upper
body temperature range is often not reached during the day in
milder climatic conditions, and therefore, the camel may not
sweat at all during the day. Evaporation of their sweat takes
place at the skin level, not at the surface of their coat,
thereby being very efficient at cooling the body compared to the
amount of water lost through perspiration.
A feature of
their nostrils is that a large amount of water vapor in their
exhalations is trapped and returned to their body fluids,
thereby reducing the amount of water lost through respiration.
They can withstand at least 20-25% weight loss due to sweating
(most mammals can only withstand about 15% dehydration before
cardiac failure results from circulatory disturbance). A camel's
blood remains hydrated, even though the body fluids are lost,
until this 25% limit is reached.
Camels in the Guelta d'Archei,
in north-eastern Chad
green herbage can ingest sufficient moisture in milder
conditions to maintain their bodies hydrated state without the
need for drinking. A camel's thick coat reflects sunlight, and
also insulates it from the intense heat radiated from desert
sand. A shorn camel has to sweat 50% more to avoid overheating.
Their long legs help by keeping them further from the hot
ground. Camels have been known to swim.
Their mouth is
very sturdy, able to chew thorny desert plants. Long eyelashes
and ear hairs, together with sealable nostrils, form a barrier
against sand. Their gait and their widened feet help them move
without sinking into the sand. The kidneys and intestines of a
camel are very efficient at retaining water. Urine comes out as
a thick syrup, and their feces are so dry that they can fuel
Domesticated camels at the
Pyramids of Giza, Egypt.
All camelids have
an unusual immune system. In all mammals, the Y-shaped antibody
molecules consist of two heavy (or long) chains along the length
of the Y, and two light (or short) chains at each tip of the Y.
Camels also have antibody molecules that have only two heavy
chains, which makes them smaller and more durable. These heavy
chain-only antibodies, which were discovered in 1993, probably
developed 50 million years ago, after camelids split from
ruminants and pigs, according to biochemist Serge Muyldermans.