654 Ecology 



the fact that the leaves are shed in the winter. There are many low- 

 growinf^ jilants, so it is possible to recognize layers within the forest. 



There are many animals eharaclerislic of this hiome. The largest 

 of these are the Virginia deer and the hlack bear. There arc also many 

 salamanders, reptiles, and even insects that are commonly fonnd. Hosts 

 of rodents inhabit the forest floor. Members of the genns Peromyscus 

 are among those most commonly fonnd. 



Again the main stress for animals is the cold of winter dnring which 

 the food snpply is rednccd. Many of the invertebrates hibernate in the 

 leaf mold, and large numbers of the birds migrate southward. 



The Prniric. — The nndulaling prairies of our western ])lains are 

 both tremendous and monotonous. The vegetation consists chiefly of 

 many grasses and large numbers of flowering composites such as the sun- 

 flowers and asters, l^xcept for some trees which grow in moist situa- 

 tions such as along rivers, there is no truly high vegetation. The eastern 

 jirairies originally had grasses as tall as a man ; further west, the vegeta- 

 tion was lower growing. Iwentually this latter merges into the des- 

 ert grassland where the rainfall is very scanty. 



The large herbivorous animals of these plains were all ungulates ; 

 the most abundant of these were the bisons which occurred in tremen- 

 dous herds. The coyote, the wolf, many lagomorphs, rmd numerous ro- 

 dents were other mammals. There are still numerous grotmd-nesting 

 birds, prairie snakes, and many characteristic insects, chiefly of the order 

 Orthoptera. 



l^'or successful survival in such a biome, it is necessary for the larger 

 animals to be swift, possess good vision, and a keen sense of smell. Many 

 of the rodents make extensive burrows. Some such as the prairie dog 

 even develop complex colonies. 



The prairies are still of tremendous importance to us for they are 

 the grain-growing and cattle-raising areas. As is to be expected, such 

 heavily utilized country has been greatly disturbed and but few natural 

 areas are to be found. 



Prairie animals nnist indeed be hardy creatures, for they mu.st sur- 

 vive not only the cold of winter but the extreme heat of stnnmer. Addi- 

 tional stresses are the heavy winds which often whip across the areas, 

 the evaporative power of the sun, and the many prairie fires. 



Desert. — The desert areas of the world are of exceptional interest 

 due to the extreme adaptations of the plants and animals dwelling on 

 them. The plants characteristically have fleshy stems, and often have 



