CHAPTER XI 

 PREDATORS 



NEED of Density Data. Most of the species of predators found in the 

 north central region are of universal distribution, in the sense that all of the 

 States lie within the exterior boundaries of their several ranges. 



Most of them are also resident yearlong, the only known exception being the 

 migratory hawks. 



Broadly speaking, therefore, variations in the damage inflicted by predators 

 upon game must arise largely from local variations in the density of predator 

 populations and from differences in food habits of the various species. 



Their food habits have been studied to some extent, but their variations in 

 density not at all. 



For this reason the attention of the survey was focused on an attempt to 

 gather evidence on the density of predator populations and to discover clues as 

 to any new factors determining such density. 



Explanation of Map 18. Crow roosts were mapped only for Wisconsin, 

 Indiana, and Missouri. Abandoned roosts were mapped only for Missouri. 



The gray fox range is complete only for Wisconsin. 



Red-gray fox ratios were determined in Wisconsin and Missouri only. Preda- 

 tor populations were obtained only in limited parts of these two States. 



The reader should notice that the sample predator populations do not attempt 

 to outline the distribution, but only give samples of the density of the several 

 species. 



FOXES 



Findings on Species Ratio. It is commonly assumed, I think, even 

 among mammalogists, that the kind and number of foxes in any locality is de- 

 termined by the type of country and the degree to which it is cleared, settled, and 

 hunted. 



A corollary assumption is that if the condition of the country remains the 

 same, the species of fox and the density of the population will tend to do likewise. 



The evidences yielded by the survey contradicts the second assumption, and 

 to a certain extent the first also. The survey indicates that: 



1. Red foxes have tended to replace grays since the settlement of the coun- 

 try. (This is well known, and is usually ascribed to the fact that the red fox is 

 more adaptable to civilized conditions.) 



2. There are certain "foxless" areas," lying usually in the prairie, or the till 

 plain type. These foxless areas are not stable. Some which were foxless 20 



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