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ECOLOGY AND WILD LIFE CONSERVATION 



remove defective birds before they can pass these defects on to their 

 offspring. 



In the same way foxes, wolves, lynxes, and cougars may be bene- 

 ficial to wild life. Rabbits often catch a disease known as rabbit fever 

 or tularemia. Unfortunately, man may catch this often fatal disease by 

 cleaning one of these rabbits. If foxes are present in the area, they will 

 be able to run down these diseased rabbits and kill them before the dis- 

 ease is spread to other rabbits. In a national park in Canada it is the 

 policy of the management to maintain a small pack of wolves to keep 

 the deer healthy and under control. In the Kaibab Refuge in Arizona 



Photo by Lovell 



Fig. 30.5. Cooper's hawk is a predator which keeps many small animals alert and 



healthy by killing the sick and physically handicapped. This hawk also prevents 



overpopulation of many small birds and mammals. 



some thirty years ago, the mule deer became so numerous that they 

 overgrazed and overbrowsed the forest land killing many of the young 

 trees and causing severe erosion. At that time wild life ecologists had 

 not discovered that large game may become too abundant for the carry- 

 ing capacity of the land. Since large carnivores such as the cougar and 

 the wolf had been exterminated, there were no predators to keep the 

 great herd healthy and in bounds. As a result of starvation and dis- 

 ease, a considerable portion of the herd perished ; but, even worse, the 

 carrying capacity of the land was permanently damaged so that the area 

 will now support less deer than before. When the wild life technicians 

 discovered it was necessary to kill off the surplus, there were so many 

 protests that it took a Supreme Court decision to settle the point that 



