8 



The Diseases and Parasites of Wild Ruffed Grouse 



Most species of vertebrate animals are subject to infection by a 

 variety of parasites, and the grouse is no exception. The proportion of 

 grouse playing host to one or more forms of parasites varies with 

 the seasons, in different regions or localities, and changes from one 

 year to another. The presence of parasites is not necessarily an ill 

 omen. How serious the infection is to the bird depends upon the 

 kind of parasite, the number present, and the destructiveness of the 

 species. 



As disease is a serious factor in the mortality rate of many animals, 

 it has long been suspected that many grouse may die from this cause. 

 Particular attention has been directed at the possible connection be- 

 tween epizootic diseases and population fluctuations, or cycles. 

 Epizootics among the red grouse ( Lagopus lagopus scoticus) in Eng- 

 land have been shown to be caused by a nematode worm ( Tricho- 

 strongijlus pergracilis) and Coccidia (Leslie and Shipley, 1911). 

 One of the early reports attributing disease as a cause of ruflFed grouse 

 scarcity was that of WoodruflF ( 1908 ) in New York. Of nine theories 

 "offered as a possible explanation of the grouse scarcity," three re- 

 lated to disease: "(5) An epidemic disease ... (6) An internal 

 parasite. (7) An external parasite ('ticks')." He concluded "that it 

 was due to an unhappy combination of three separate factors, each 

 one of which alone was serious in its effects." Following winter 

 predation and adverse spring weather in 1907, number three is "an 

 epidemic of some disease or parasite, or both, just which we cannot 

 now determine." 



However, the report on the next die-oflP in New York (Stoddart, 

 1918) deprecated disease as an important factor. After recalling the 

 importance that Woodruff attached to disease in the earlier report, 

 Stoddart says: "There is nothing in Mr. Woodruff's report that is 



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