 Juvenile tortoises eat an average of 16.7% of their own body weight in dry matter per day, with a digestive efficiency roughly equal to that of hindgut-fermenting herbivorous mammals such as horses and rhinos.Tortoises acquire most of their moisture from the dew and sap in vegetation (particularly the "Opuntia" cactus); therefore, they can survive longer than 6 months without water.They can endure up to a year when deprived of all food and water, surviving by breaking down their body fat to produce water as a byproduct.