The hump of a camel is actually filled with fat. That store of fat is like a spare tank of gasoline in a car trunk. When food and water become scarce, the camel extracts energy from that mound of fat. In fact, the longer a camel goes without eating or drinking, the more visibly deflated its hump becomes. But give it adequate water and food, and camel humps plump up in a matter of days.
When temperatures rise above 110 degrees Fahrenheit, camels can survive for about five days without drinking water.
During the winter, camels can survive six or seven months without drinking water. During that time, they may obtain moisture from the plants they consume.