Camels" bodies are perfect for long desert travel: their broad feet make walking on sand easier; their long eyelashes protect their eyes from sand; and their nostrils close to keep sand out. The hump on their backs is actually a deposit of fat, stored energy for when the next oasis is miles away. Camels can survive without water for really long periods of time and can lose over forty percent of their body weight in water. Most animals can only safely lose twenty percent. Even when water is not readily available, camels produce milk that is a staple food to nomadic tribes in the desert. Compared to cow milk, it is richer in both protein and fat.