two seasons of the year, in southeastern Arizona at least, when storage
of food takes place, namely, in spring, during April or May, and in
fall, from September to November, the latter being the more important.
For the periods between, the animal must rely largely on stored
materials. Not infrequently a season of severe drought precludes the
possibility of any storage. The summer and fall of 1918 was such a
season on the Range Reserve (Pl. II, Fig. 2). If food stores are
inadequate at such a time the kangaroo rats must perish in considerable
numbers. Fisher found many deserted mounds in the vicinity of Dos
Cabezos, Ariz., in June, 1894, which may be accounted for in this way.
In 1921 Vorhies found all mounds within 4 or 5 miles of Albuquerque, N.
Mex., deserted by _spectabilis_, resulting probably from overgrazing by
sheep and goats during a succession of dry years. In the arid Southwest
natural selection probably favors the animals with the largest food
stores, and it is not surprising that the storing habit has been
developed to a remarkable degree.

Some stored material is likely to be found at any time of year in any
mound examined, the largest quantity usually in fall and winter, the
smallest in July or August (Table 1, dens 1, 2, 14, and 24). Amounts
found by different observers vary from a few ounces to several quarts or
pecks, and stored materials taken from 22 mounds on the Range Reserve
vary in weight from 5 to 4,127 grams (more than 9 pounds). This is
exceeded by one lot from New Mexico, which totaled 5,750 grams (12.67
pounds). It is fairly evident that in seasons of scanty forage for stock
the appropriation of such quantities of grass seeds and crowns and other
grazing materials by numerous kangaroo rats may appreciably reduce the
carrying capacity of the range. Studies of cheek-pouch contents and food
stores taken from dens show that the natural food of _spectabilis_
consists principally of various seeds and fruits, particularly the seeds