198 The Ruffed Grouse 



complete story. From the standpoint of the prey species, the per 

 centage of its population that the predator takes is all that counts, 

 regardless of its ranking in the predator's diet. As a problem in the 

 food habits of a predator, the volume of food that a prey species 

 furnishes is all that matters at the moment, aside from the effect on 

 the status of the prey species. To illustrate let us take a hypothetical 

 case. We have two situations. In the first we have one family of foxes 

 and one hundred grouse in a covert. In the second we have one 

 family of foxes and ten grouse. Let us assume in each case that the 

 foxes take ten grouse. In the first instance the prey species is little 

 affected, losing only ten per cent of its numbers; in the second it is 

 entirely wiped out. Yet in both cases the grouse furnished the same 

 part of a fox family's diet. Let us assume it was two per cent. It was 

 relatively unimportant to the predator, but to the prey species in 

 one covert it was fatal. 



Now let us begin over and take a different course with the same 

 data. Say the foxes take fifty grouse in the first situation and none 

 in the second. Then the grouse becomes a big item of food, ten per 

 cent, to the fox in case I, without critically damaging the prey spe- 

 cies, while in the second case, though the fox has not gained, there 

 are fewer grouse than are left from the preyed-on population. 



Thus the importance of prey species as food and the importance 

 of predators as enemies are relative matters that must be correlated 

 with other food habits and with population data to be properly ap- 

 praised. Since we are concerned primarily with the grouse, we will 

 examine the effect of the predatory species on this species, even ff 

 grouse is not an important item in their diets. We will also give some 

 information on the part that grouse play in the subsistence of the 

 various predators. It can be said categorically, however, that the 

 grouse is rarely an item of vital importance in the diet of any preda- 

 tory species, except possibly the goshawk. 



Red and Gray Foxes. Both species of foxes native to the Northeast 

 commonly take grouse. As predators, one is about as efiicient as the 

 other, and the relative importance of either one is generally in pro- 

 portion to its abundance. The red fox is common throughout the 

 Northeast, whereas the gray is found mainly from central-New York 

 southward. So far as we know, their effects on grouse are much the 

 same, therefore we will discuss them together. 



