People used to think that the camel’s hump was a storage place for water. But the hump on its back is mostly fat.  Camel’s live in the desert, and they often have to go a long time without food. When food is scarce on long desert treks, the fat in the hump provides energy for the animal.

When the camel has not eaten for a few days, its hump gets smaller.  After the camel has had a few days’ rest and some foods, its hump becomes firm and plump again.  The camel must drink water.  But once it drinks, it can go for days without drinking again. – Dick Rogers