Contrary to popular belief, camels do not store water in their humps. Instead, they store energy-rich fat deposits. The humps are used as a source of nourishment when food is scarce, and the fat inside the hump is metabolized for nutrition. The humps can deflate and droop if the camel has gone a particularly long time without food, but they will sit upright again once the camel is able to refuel. The size of the hump changes depending on how much food the camel eats. Camels can go for long periods of time without water, and they drink large amounts of water - up to 20 gallons at a time - which is stored in their bloodstream.