224 Game Survey of the North Central States 



to occupy the rough, broken terrain, especially that offering limestone ledges. 

 The second theory, however, is apparently contradicted by the reappearance of 

 grays in Ripley and Callaway Counties, Missouri, during the same year (1918) ; 

 by Ochsener's observation on the increased proportion of grays in Sauk County, 

 Wisconsin, since 1925; and especially by Brooks' observation that in 1918 Ripley 

 County was all grays, although it has since changed to all reds. There are posi- 

 tively no visible modifications of the terrain sufficient to explain these shifts in the 

 ratio. Moreover, why are there no grays in Dent County, Missouri, which is 

 almost entirely composed of the kind of range which grays are supposed to prefer? 



The foregoing evidence, in my opinion, does not make it necessary to dis- 

 card the two popular theories, but it does indicate very strongly that some in- 

 visible factor is at work which neither theory takes into account, and which is 

 sometimes more powerful than either of them in determining the species ratio 

 and species distribution. This conclusion is further strengthened by the great 

 difference in fox populations per unit area in apparently similar environments 

 discussed in the next caption. What can this invisible factor be? 



It must be something that changes more rapidly and more often than the 

 visible environment. There was no change in the visible environment of Ripley, 

 Callaway, or Sauk Counties which could account for the reappearance of grays 

 above described. The invisible factor which could most probably account for 

 such puzzling shifts and changes is disease or parasites. 



Fox Populations. Two localities were encountered in Missouri where a 

 virtual "clean-up" had been made on foxes in the course of the state's predator- 

 control work on refuges. Table 50 reduces the kill to a "foxes per township" 

 figure by making certain arbitrary allowances for influx during the control period. 

 A similar calculation was made in Grant County, Wisconsin, with the help of a 

 local fox hunter. 



Section B of Table 50 gives some estimates of "foxes per township" made 

 by selected fox hunters in Missouri. 



Locations of all these population figures show on Map 18. 



Fox-Quail Ratios. The lowest fox population for Missouri shown on 

 Map 18 is four foxes per township near Doniphan in Ripley County, and the 

 highest is 85 foxes per township in Meramec State Park in Franklin County. As- 

 suming these two figures to represent the two opposite extremes of fox abundance, 

 it is evident without further argument, that the depredations by foxes on game 

 must depend more on fox abundance than on fox habits. Chart 1 indicates that 

 in the_Qzark types the most frequent density of quail populations is a quail per 

 four acres. If in Ripley County there is one fox per 6,000 acres, there would be 

 1,500 quail for each fox. 



On the other hand, in Franklin County, which has 85 foxes per township 

 and quail about the same as in Ripley, there would be one fox for each 300 

 acres, and only 75 quail for each fox. 



