ROLE OF PREDATION 329 



since on such occasions both grouse and buffer populations have been below average. It is, 

 therefore, more probable that the increases in tracks recorded in 1936-37 and 1939-41 were in 

 the main the result of greater activity associated with times of scarcity among small mammals. 

 Figure 30 illustrates this relationship. 



Rabbits seem to exert a somewhat greater influence than mice and shrews. Their drop from 

 1936 to 1937, while the latter remained constant, was accompanied by an increase in the oc- 

 currence of fox tracks. Conversely, from 1938 to 1939, despite a sharp decrease in mice and 

 shrews, a greater rise among rabbits was associated with a moderate reduction in fox activity. 

 That mice may nevertheless be important was indicated in 1937-38 when their high abundance 

 apparently offset a severe low in rabbits. 



The fact that fewer fox tracks were not recorded in 1934-35 when both small mammal 

 groups as well as grouse were very abundant seems somewhat contradictory. Yet it may be 

 that a fox will travel about so much at this season regardless. 



Another reason for believing that the fox track data represent activity is the fact that the 

 number of droppings picked up by field crews over the same period has varied inversely. 



Undoubtedly the great horned owl and other predators react similarly although the data 

 have not been sufficient for correlation. 



With respect to pressure on grouse it follows that the more time a predator spends on 

 the move the more often it will encounter grouse and have opportunities to prey on them. 

 The situation appears to parallel the old adage, "you won't catch manv fish if vou don't 

 keep your line wet". 



Grouse : Predator Ratios 



An important part of any study of the role of predation is a knowledge of the complexion 

 and size of the predator population involved in comparison with that of the game. During 

 the Investigation, however, it has not been feasible to undertake actual censuses of these 

 species. Nevertheless, various data have been recorded which, supplemented bv observations 

 during the regular grouse survey work each year and by the cumulative experience of the 

 authors, make possible a reasonably accurate appraisal of the situation on the areas most 

 intensively studied. 



On Connecticut Hill, which is essentially representative of the better grouse coverts of the 

 State south of the Mohawk River, the principal grouse predators were the fox*, weasel, skunk, 

 raccoon, great horned owl, Cooper's hawk and sharp-shinned hawk. With respect to this 

 area predator control experiments carried on during 1931-32 and 1933-34 afford a basis for 

 a rough estimate of abundance for all except the hawks. The numbers taken per square mile 

 averaged fox — 3, weasel — 5, skunk — 6, raccoon — 2 and great horned owl — 9. 



These data are conservative because no species was eliminated. Furthermore, they pri- 

 marily represent the fall to spring period. During the season when young are present num- 

 bers would usually be higher except in the case of the great horned owl. Here the great 

 majority of the birds trapped apparently were winter visitants. Breeding populations of 

 this owl probably seldom exceeded two pairs per square mile. As pointed out under a pre- 

 vious topic'^ the numbers of these species have not varied greatly on this area during the 

 years covered. 



While occasional Cooper's hawks often remain through the winter the sharp-shinned hawk 



* The ratio of red foxes to gray foxes on this area was about 3 to 1. 

 A See discussion of Predator Fluctuations, p. 323. 



