102 ANIMAL LIFE IN DESERTS 



a fauna is found after rain, between the trunk and 

 the leaf -bases of the date palm ; this fauna is rela- 

 tively rich and contains all the groups which I have 

 just enumerated as characteristic of stone and earth 

 desert in spring. In fact, one may say that the 

 animals which shelter in the date-palm in Mesopo- 

 tamia are the biological counterpart of those found 

 under stones in Persia or Palestine. To what 

 extent the same genera or species of animals are 

 represented in both we do not at present know. 



Other animals which are unable to endure the 

 climate of the surface of the desert dig burrows 

 or use burrows which have been excavated by other 

 creatures. They thus easily reach a zone in which 

 temperature and humidity are nearly constant 

 (page 22). In the group of active burrowers fall 

 certain lizards and snakes, and nearly all the small 

 rodents (Jerboas, Gerbils, Spiny Mice, and many 

 others), and some at least of the small marsupials 

 of Central AustraHa. Many observers have not" ed 

 the extraordinary abiUty of the House Mouse (Mus 

 musculus) and its very close relatives {Mus gentilis 

 and other forms) to colonize human habitations 

 in nearly every part of the Great Palaearctic Desert : 

 the rapidity with which they become abundant in 

 isolated camps in Mesopotamia was frequently 

 noticed. These animals are protected from great 

 fluctuations of heat and relative humidity by their 

 burrows which are made beneath houses, and be- 

 cause they frequently travel from place to place 

 in boxes and bales. If they were diurnal and Uved 

 openly in man's habitations they would be faced 



