ANIMAL CHEMISTS CHANGE STARCH INTO WATER
One of the most striking modifications of mammalian economy by environment is that shown in many small mammals of our southwestern desert region and adjacent parts of Mexico, in which such species as the kangaroo-rats, pocket-mice, prairie-dogs, and others are able to exist under the most arid conditions without drinking. The liquid necessary for supplying their bodily needs is obtained through chemical action in their digestive tracts, whereby some of the starchy parts of their food are changed into water.
Over considerable areas in the waterless deserts on the peninsula of Lower California periods of from three to five years sometimes pass without a drop of rain falling. In these areas the small desert mammals named above, as well as wood-rats, white-footed mice, cottontails, and jack-rabbits, are numerous and successfully pass these dry periods without inconvenience. The absolute independence of water of these animals has been demonstrated in southern California in the case of pocket-mice kept for months in captivity in a box and fed solely upon thoroughly dried seeds without their showing the slightest sign of discomfort.
Our small mammals may be roughly classified by their food habits into three main groups: Rodents, or gnawing animals; carnivores, or flesh eaters, and insectivores, or insect eaters.