The humps the backs of camels store excess fat, not water. These fats act as reserves, providing them with both nutrients and water they need when food and water are scarce.
Kangaroo rats are one of the most water-thrifty animals! They hardly lose any water through sweating, panting or even in their urine!
Feeding on plants and insects in the desert provides the jerboa with all the water they need to survive! This means they do not need to find water in water-scarce deserts.