What secrets lie within |
 At last, the water-hole (copyright 1996 Corel Corporation) |
It is common knowledge that dromedary camels can survive for many days in the hot desert without access to water. However, the role of the camel's hump in water preservation is not as well understood. Most of us, when looking at camels in the zoo, still imagine the humps to be filled with water. But what is the truth behind the myth - what secrets are hidden beneath the camel's skin?
Firstly, it can be ascertained that the camel's hump is not in fact filled with water, simply by cutting into it. Such action would reveal that the hump is in fact composed mostly of fat. Yet, this could still suggest that the hump acts as a water store - if a gram of fat is broken down during metabolism, it produces more than a gram of water. However, camels cannot use this fat for water production - due to the arid conditions prevailing in their habitat, they would lose too much water across their lungs in obtaining enough oxygen for fat degradation.
So, what is the role of the camel's hump? Unfortunately the answer is relatively dull - it appears that the humps are merely food reserves, and the fat and flesh contained within are absorbed as nutrition when food is scarce.
Then how exactly do camels get water? When dehydrated camels are offered water, they drink and they drink a lot. It is uncertain whether they drink more than they have actually lost. If they do, they store some water, not in their hump, but in their diluted body fluids. Camels also have an exceptional ability to minimize their water losses (see related articles by Jenny Fredriksson and Maria C Hansson).
Although the myth that the camels' humps are filled with water has been dispelled, this does not change the fact that, physiologically, camels are incredible animals.
Note: You might ask why the fat depots of the dromedary camel are situated on the back of the animal, not all around the body as in seals and whales. An additional function of the hump is probably to insulate the camel from solar radiation. The desert sun certainly shines mainly from above. Fat-containing adipose tissue is suitable for insulatory purposes, because fat conducts heat slower than water. Also blood flow can be very low in adipose tissue, because the fatty deposits do not need oxygen. This further contributes to the insulatory function of the hump. The dromedary camel is also equipped with a very thick fur on its back while the fur is thinner elsewhere. The thick dorsal fur provides additional isolation from the sun, while the thin fur allows for heat loss from other parts of the body.
AL
Reference
R.W. Hill and G.A. Wyse: Animal Physiology (2nd ed, HarperCollins, 1989).
