Desert species, such as the spiny mouse, can survive happily without any external source of water. As an extra water conservation measure, such species produce only limited amounts of droppings and a highly concentrated urine. Some spiny mice can live purely on tiny quantities of sea-water and even your ordinary house mouse can get by almost indefinitely without liquids.

This does not mean that you should ever leave your tame mice without a source of fresh, clean water! They are domesticated varieties which may not be as hardy as their wild cousins.