The white-throated wood rat, Neotoma albigula, may go its whole life without ever taking a drink of water. It does not need to. The rat obtains all the water it needs from its food. The fact that the rat's diet includes dry seeds and cactus makes this even more surprising. It obtains about half of the water it needs from succulent plants. The white-throated wood rat is also able to chemically synthesize water from the molecules in the food it eats. It shares this adaptation with many other Neotoma species, also known as pack rats. The wood rat has many other adaptations that allow it to thrive with little or no water.

The small kit fox, Vulpes velox, rarely drinks water. It will if it is thirsty and has the opportunity, but it is generally a long way from the...