Small mammals abound in the high desert areas of southeast Arizona. Many of them are seldom seen because of their nocturnal habits. Their small size allows them to escape the heat of the day by remaining in underground burrows, emerging to forage at night.
Many of these tiny creatures need little or no free water from rainwater or ponds since they are able actually to make the water they need from chemical elements in their food. According to Dr. Knut S. Nielson, "Even the driest seeds contain some absorbed water, but a larger quantity is formed by oxidation of food in the body. On oxidation one gram of starch yields 0.6 gram of water and one gram of fat yields almost 1.1 grams of water. By exercising the greatest physiological economy ... these small rodents can just manage on the oxidation water, being independent of intake of free water."*
Small nocturnal animals are able to avoid using water for heat regulation by remaining in cool underground burrows during the day. Larger mammals, who cannot escape the heat as effectively in this way, need to cool their bodies by evaporation, through sweating or panting.
* Nielsen, Knut Schmidt. "Animals and Arid Conditions," The Future of Arid Lands. Washington, D.C.: American Association for the Advancement of Science, 1956.
Merlin, Pinau. A Field Guide to Desert Holes, Revised Edition . Tucson: Arizona-Sonora Desert Museum Press, 2002. A good guide to finding the homes of the many small animals that spend the day in underground burrows. This revised edition includes 50 full-color photos, a great improvement on the previous edition.
Tekiela, Stan. Mammals of Arizona Field Guide (Arizona Field Guides). Cambridge, MN: Adventure Publications, 2008. A small format book just packed with information about all the mammals you might find in Arizona from the tiny desert shrew to the black bear. There are 3 pages of information on each animal, plus a full page photo and several smaller photos.