322 



PREDATION 



It seems sigiiificanl that these forces reached their highest level on Connecticut Hill in 

 1936-37, when buffer species were at their lowest ebb. Yet they were most severe in 1934-35 

 on the Adirondack area where the drop in abundance of hares ( Lepiis americanus) came 

 earlier than that i!i cottontails I Sylvilagus jloridanus) on the other tract. 



On the Connecticut Hill area the great horned owl (Bubo viry,inianus) has been a major 

 predator during the adult period. In figure 28 is also graphed the incidence of grouse in 

 the pellets of this owl collected each year. There is a strong siniilarit\ between this and the 

 deviation from average of the adjusted degree of overwinter loss. 



Shown also is the relative trend in buffer abundance from 1933-31 through 1910-11. It 

 seems significant that in 1936-37, when the greatest increase in overwinter mortality occur- 

 red, the frequency of grouse in these pellets should have been the highest of the series and 

 should have been accompanied by the greatest scarcity of buffers recorded. Furthermore, 

 records of the survey give some indication that 1932-33 also witnessed a low level among 

 rabbits and mice. In 1937-38 while rabbits were still scarce but mice and shrews had 

 increased the incidence dropped but so also did the fall population le\el and the general 

 overwinter loss. That the pellet representation in 1934-35 was not lower mav have resulted 

 from the fact that the grouse population in the fall of 1934 was next to the highest recorded 

 during the study. The data suggest that the abundance of buffers, through its effect on the 

 amount of time jjredators spend in hunting, exerts an effect on h<jw often they will cncduritcr 

 grouse. 



As discussed under another topic fox activity on this area has also lluctuated from year to 

 year inversely to buffer numbers. In this case, while there appears to be a correlation in 

 point of time with variations in overwinter loss, analysis of fox droppings does not substan- 

 tiate an actual relationship. Table 39 presents the occurrence of grouse in this material. 



TABLE 3y. 



INCIDKNCE OF GROUSE KEMMMS IN FOX OUOI'PINGS— CO.NNECTICIIT 



HILL AREA— 1930- 1911 » 



* Dates correspond with those in table 38. 



Oddly enough a higli representation occurred in 1934-35 wlicn iiuffcrs were most numerous 

 while in 1936-37 the situation was reversed. The increase in llic rniinber of scats collected 

 from 1935-36 on was due to a larger area being covered and more stress being laid on 

 this j)hase of the work. The interpretation of this data is not clear. Apparently fox |)reda- 

 tion on adult grouse is much less affected by l)uffer aliimdiinic iIkiii with the great huriicd owl. 



,\s discussed elsewhere* niortalil) among adult grouse is greatest (luring the late winter. 

 Since predation seems to be the major decimating agent invoKed it follows that it is most 

 effective during this critical piiiiKJ wiiin environmental conditions are most severe, buffer 

 foods least available and the grouse at a low |)h\sical ebb. There has been no noticeable dif- 

 ferential between the sexes exce|)t that the males appear to be somewhat more vulnerable dur- 

 ing the drumming season. 



• See Chi|.ter XU. p. 536. 



