ANIMALS THAT LIVE WITHOUT WATER 153 



in both bees' and birds' nests, until at the peak of the 

 season the once seemingly barren region is well popu- 

 lated. Each new inhabitant brings in its wake those who 

 prey upon it, until even coyotes, foxes and other car- 

 nivores can invade the waterless wastes with some de- 

 gree of safety. 



A favorable year climatically is accompanied by en- 

 hanced growth and numbers of all animals; an unfavora- 

 ble year reduces both the adult size and the number 

 of offspring and, if drought is abnormally prolonged, the 

 species may be so reduced that several years are re- 

 quired to re-establish it. There is no evidence that the 

 fertility or reproductive rate in any species whatsoever 

 is stimulated by adverse conditions. 



It is not, however, among the carnivores that we find 

 the most successful mammaUan invaders of the desert, 

 but among the herbivores which live directly on the des- 

 ert vegetation. The reason for this seems clear enough: 

 except for those that hibernate in cold weather, the 

 mammals, unlike the insects, must be active the year 

 around; and although some of them may migrate to 

 more favorable areas, as do the birds, they must in gen- 

 eral reproduce and rear their yoxmg under strictly des- 

 ert conditions. To colonize the desert successfully, the 

 mammals must feed directly on the land and not on its 

 seasonal population. 



Thus it is that many large, herbivorous mammals, 

 such as the giraffe, eland, antelope, and gazelle, seem 

 able to sustain themselves in desert areas far from any 

 source of drinking water. The gazelle's abihty to do with- 

 out water probably accounts for the fact that it is seen 

 more frequently than any other mammal in many of the 

 world's deserts. 



Unfortunately, there are almost no rigidly controlled 

 observations in these matters, and much that passes for 

 fact is mere legend. The legend of the camel, for ex- 

 ample, is notorious, but the legend is unquestionably ex- 



