Great Mythconceptions by Karl Kruszelnicki

Author:Karl Kruszelnicki
Language: eng
Format: epub, azw3, mobi
Publisher: HarperCollins Publishers
Published: 2004-07-16T16:00:00+00:00

Camels do not store water in their humps. Instead, the hump is used to store most of the camel’s fat — up to 35 kg. (This explains why the meat from the rest of the camel is quite low in fat.) One advantage of having so much fat stored on the camel’s back is that it insulates the camel from the heat of the desert sun. The fat also acts as an insulator in another way. Fat usually has a very poor blood supply. So even if the fat does get warm, it can transfer only a very small amount of heat to the total blood circulation of the body.

The camel’s hump is predominantly a massive food reserve, not a water store. The price it has to pay to access this potential food, is that it loses lots of water vapour from its lungs. When a camel burns a gram of fat for energy, it produces more than a gram of water. But to do this, the camel burns up a lot of oxygen which requires lots of extra breathing — and as it breathes out, it loses much of its water.

How then can a camel go without water for 17 days and survive?

First, camels have evolved so that they can lose up to 25% of their body weight without ill effect. Human beings can’t do this easily.

Second, they have evolved in ways to conserve water. They lose very little water in their urine, because their kidneys have a massive concentrating ability, so their urine is like syrup. Their faeces contain so little water that when the round dry pellets pop out, they can be burned as fuel. Camels adjust their body temperature to suit the environment (ranging from 34–41.7ºC), and rarely have to waste water by sweating. And when they need more water, they remove it from everywhere in their body except the bloodstream. Their body dehydrates, but the blood circulates normally and does not ‘clog up’. No other mammal can do this.

Finally, when they do get near water, there’s no horsing around. They can drink as much as a hundred litres in 10 minutes. Their gut can release this very large volume of water very slowly, so that their internal metabolism is not suddenly overloaded.

Camels do not carry water in their hump — and if they were designed by a committee, the members did a very good job.

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