2 ECOLOGICAL FOUNDATIONS OF ZOOGEOGRAPHY 



controlling factors; but the solution of its problems is not, therefore, 

 less attractive or important. 



The gradual development of the study of animal geography makes 

 it possible to distinguish a number of diverse lines of research, which 

 appeared one by one with the advance of this department of science. 

 The origins and foundations of zoogeography lie in the accumulation 

 of faunal lists, in which the animal populations, whether for single 

 groups or in toto, are enumerated for specified areas of varying extent. 

 This is the function of "faunal zoogeography" which goes hand in 

 hand with the identification of animal species and in general with 

 the accumulation of collections. These studies are not equally advanced 

 in the various groups of animals. Classes and orders whose representa- 

 tives are notable for their beauty, brilliant coloration, or diversity of 

 form, or whose simplicity of preservation encourages collecting, such 

 as birds and mammals, beetles and butterflies, snails and mussels, 

 have always been more intensively collected and studied than such 

 groups as the hydroids, may flies, springtails, squids, or earthworms. 

 Faunal zoogeography, in identifying animals and putting in order 

 a wealth of data, forms the basis for every further development of 

 the subject. Extraordinary advances have been made in this direction 

 during the past ninety years. Important scientific expeditions have 

 brought together great numbers of museum specimens from distant 

 countries and seas, and these have been described and classified. The 

 record, however, is far from complete for the smaller, less conspicuous 

 forms, even in the most highly civilized countries. 



Animal life is very unequally distributed in any considerable area. 

 Various habitats, or biotopes, can be distinguished, according to soil, 

 vegetation, and climatic conditions, each inhabited by a definite and 

 well-characterized animal community. The determination of well- 

 defined biotopes and their "indicators," with the intensive study of 

 the associated animals, constitutes an additional problem for faunal 

 zoogeography which will require much further study. This set of 

 problems is being attacked by the ecologist in his studies on the com- 

 position and organization of animal communities. 



Instead of proceeding from a geographic unit area, a zoologic 

 unit group may be the starting point. In addition to determining the 

 species of animals for a given region, the specific areas, or ranges, of 

 the individual species must be exactly defined. The ranges of species 

 which occur together in a given locality may be entirely unlike. 

 Giraffes, rhinoceroses, zebras, and antelopes are found together in the 

 steppes of central Africa. The giraffe ranges from the Orange River 

 to the Zambezi, but apparently never occurred south of the Orange. 



