Ecology of Anhnals 671 



Introduction of New Forms. — The introduction of new forms 

 into an area may have as deleterious effects as the removal of some one 

 form. This, too, has been shown repeatedly. 



In the early 1800's some homesick Englishman introduced five 

 rabbits into Australia — chiefly so that he could go hunting. The rab- 

 bits in this new area, without natural predators or parasites, spread 

 with tremendous rapidity over most of Australia. By 1920 they were 

 found in three-fourths of the country and were threatening the sheep- 

 raising industry due to their destruction of vegetation. 



Here in the United States, the introduction of the English sparrow 

 at first raised havoc with our native birds. It is an aggressive ani- 

 mal, well able to take over nesting sites and available food. It was 

 thus competing with the native birds and actually being more successful 

 for it had no natural enemies. At present it has achieved somewhat 

 of a balance in its chosen habitats. 



Even more harmful has been the accidental introduction of agricul- 

 tural pests. This was much more common in the past than at present, 

 for now strict examination of plants entering the country is required. 

 The European corn borer, the gyps}- moth, and many other harmful 

 forms can be included here. 



Conservation thus has many facets. It includes the preservation 

 of natural areas and their fauna and flora as well as the intelligent 

 use of our lands, forests, and waters. Any program involving the use 

 of these resources can be successful only as it is based upon sound 

 ecological principles. 



