POCKET MOUSE 



extent, in dry, open forests in the Southwest. They are bur- 

 rowing Mice and are found in greatest abundance where loose 

 soil or sand makes burrow construction easy. The burrows 

 are made only as homes and the Pocket Mice come forth at 

 night to run about like other Mice, not spending the greater 

 part of their existence underground like another pocketed 

 rodent, the Pocket Gopher. 



Pocket Mice are strictly nocturnal and over much of the 

 range of the group this habit is a decided advantage. 

 Although a few forms reach well up on the cooler prairies, 

 the group is typically Sonoran in its distribution, and the 

 greatest number of species is found on hot, arid plains or 

 stark desert tracts where a hot sun makes daylight activity a 

 heavy drain upon mammal activity. Some of the mammals 

 of these areas are diurnal and withstand heat and dryness 

 successfully, but Perognathus avoids these features by coming 

 out only after sundown. Most of the Pocket Mice are also 

 of light coloration, sandy grays or light browns and buffs, 

 which is an adaptation to desert conditions. 



The presence of Pocket Mice is usually easily detected by 

 their burrows and their paths or runways over the sand. • In a 

 grassy country these may not be so obvious, but in sandy, 

 desert sections the mouse "sign" is conspicuous. The bur- 

 rows are often plugged with sand a short distance in from the 

 entrance to keep out snakes, light, or heat, perhaps all external 

 disturbances. These Mice are rather social in habit and a 

 hummock of sand may be honeycombed by interior workings, 

 with several external openings. Tracks radiating out from 

 the holes indicate the presence of several animals and inspec- 

 tion each morning will show that there has been great activity 

 the night before. 



The cheek-pouches are used for storing seeds and hold a very 

 sizable collection. The animal picks up seeds and grains of 

 all sizes, some of which are very tiny, and carries them to an 

 underground storehouse. Despite the fact that most of the 

 food these Mice eat is very dry, they are capable (at least 

 the desert species are) of going indefinitely without water. 

 Pocket Mice are easily tamed and make interesting pets, 

 although because of their nocturnal habits they are difficult 

 to observe. 



The number of young varies from four to seven but is usu- 



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