| | | | 1921. | | | | | 22 | Jan. 1 | 2,333 | Fair. 23[4] | Nov. 7 | 1,685 | Good. 24[4] | Nov. 8 | 5,750 | Do. | | | ------------+-----------+-----------+----------- [Footnote 3: Changing from poor summer season of 1918 to excellent spring growth of 1919.] [Footnote 4: From near the Sandia Mountains, N. Mex.; others from United States Range Reserve, near the Santa Rita Mountains, Ariz.] In presenting Table 2, showing quantity of storage per burrow correlated with the time of year and the character of the preceding growing season, the fact may be emphasized that the growing seasons in southern Arizona are two in number--early spring and midsummer. The spring season is the less important, the plants consisting chiefly of a variety of small annuals, while the important range grasses make their chief growth and head out almost exclusively in the July-August rainy season. It may be noted also that the actual increases in storage appear somewhat after the growth period proper, since storing does not get well under way until the seed crop is mature. The banner-tailed kangaroo rat shows a marked adaptability to different foods available in the neighborhood of its burrows. It must, perforce, adapt itself and its storage program to the food that it can get, and this varies enormously with the climatic conditions of successive seasons. The large numbers present in suitable localities clearly indicate that the animal is successful in meeting the changing and sometimes extremely adverse conditions of its environment. [Illustration: PLATE VIII. FIG. 1.--CONTENT OF DEN EXCAVATED IN NEW MEXICO. Storage content of Den No. 24, of Table 1, from Sandia Mountains, N. Mex. This is the largest lot of storage taken in the course of the investigations. The larger pile consists wholly of a valuable grass, _Sporobolus cryptandrus strictus_: the smaller of Russian thistle (_Salsola pestifer._)] [Illustration: PLATE VIII. FIG. 2.--GROWTH FOLLOWING ELIMINATION OF KANGAROO RATS. The same mound as shown in Plate III, Figure 1, after three years of protection, the rodents having been killed out. Nearly as good grass recovery following poisoning operations occurred in the single excellent season of 1921.]