ifxp^Ste } LIFE HISTORY OF THE KANGAROO RAT. 25 



inci'eases in storage appear somewhat after the gro^Tth period proper, 

 since storing does not get well under way until the seed crop is 

 mature. The banner-tailed kangaroo rat shows a marked adapt- 

 ability to different foods available in the neighborhood of its bur- 

 rows. 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 suit- 

 able localities clearly indicate that the animal is successful in meet- 

 ing the changing and sometimes extremely adverse conditions of its 

 environment. 



At times, more especially in the seasons of active growth, some of 

 the green and succulent portions of plants are eaten. This was very 

 noticeable in the spring of 1919, when a most luxuriant growth of 

 Mexican poppy {Eschscholtziamexicana) occurred. Stomachs at this 

 time were filled with the yellow and green mixture undoubtedly pro- 

 duced by the grinding up of the buds and flow^ers of this plant. 

 Small caches of about a tablespoonful of these buds were also found 

 in the burrows at this time. Occasionally in spring one may find a 

 few green leaves of various plants, Gaertneria very commonly, 

 tucked away in small pockets along the underground tunnels, indi- 

 cating that such materials are used to some extent. As has been 

 shown in detail, however (Table 1), the chief storage, and undoubt- 

 edly the chief food, consists of air-dry seeds. 



The character of the storage, the absence of rain for months at a 

 time in some years, and the consequent failure of green succulents 

 show that without doubt spectahilis possesses remarkable power, as 

 to its w^ater requirements, of existing largely if not wholly upon the 

 water derived from air-dry starchy foods, i. e., metabolic water serves 

 it in lieu of drink (Nelson, 1918, 100), this being formed in con- 

 siderable quantities by oxidation of carbohydrates and fats (Bab- 

 cock, 1912, 159, 170). During the long dry periods characteristic 

 of southern Arizona, no evidence that the animal seeks a supply of 

 succulent food, as cactus, is found; and if it may go for two, three, 

 or six months without water or succulent food, it is reasonable to 

 suppose that it may do so indefinitely. In the laboratory spectabilis 

 ordinarily does not drink, but rather shows a dislike for getting its 

 nose w^et. During the periods of drought the attacks upon the 

 cactuses by other rodents of the same region, as Lejpus^ Sylvilagus, 

 Neotoma^ and ATwrnospermophilus^ become increasingly evident. 

 The list of plant species thus far found represented in the storage 

 materials of spectahilis on the Range Reserve is shown in Table 3. 



