CONTROL OF ASSOCIATED ORGANISMS 671 



Control of Disease 



From the data at hand the grouse manager will seldom, if ever, be faced with a serious dis- 

 ease problem. So far nothing even approaching an epizootic has been encountered in New 

 York birds. On the other hand, there has been no opportunity to study a period of pro- 

 nounced cyclic decline in abundance. 



Thus, the possibility should not be ignored. In the first place, disease is the result 

 of influences or conditions to which the bird is subjected. These underlying causes may be 

 mechanical, chemical, nutritional or parasitic. Since medication or other treatment of wild 

 populations is practically impossible, control measures must be directed toward removing 

 the cause. 



Few definite recommendations can be made with respect to grouse because the conditions 

 necessary for experiments of this kind have seldom occurred during the Investigation. It may, 

 however, be of interest to consider some of the measures which have been used effectively in 

 connection with other species. For example, botulism, a condition in which waterfowl are 

 poisoned by the waste products of certain bacteria, has been controlled by changing the 

 water level and by the establishment of certain plants which destroy the bacteria. Again, 

 eradication of hoof-and-muuth disease among California deer was accomplished by actually 

 eliminating these animals from the affected region. In Wyoming, the incidence of necrotic 

 stomatitis, a serious bacterial disease among elk, was lowered by removal of certain grasses 

 from the range. In Britain, losses among the Scotch grouse from coccidiosis and certain worm 

 parasitism have been reduced by burning the moors and draining low damp areas, thus expos- 

 ing the eggs and other immature stages of the organisms to the direct drying and irradiating 

 effects of the sun. 



In cases where an intermediate host is involved in the life cycle of a parasite, it is some- 

 times possible to break the chain of transmission by destroying this link. Some of the fluke 

 diseases of domestic animals can be controlled by poisoning the snails in which the early 

 stages of these flatworms develop. 



If it should ever become necessary to combat an established disease condition among rufled 

 grouse, effective procedures will undoubtedly follow some such course as the above. 



But "an ounce of prevention is worth a pound of cure". Although normallv latent, organ- 

 isms capable of giving rise to an epizootic are ever present. They need only favorable condi- 

 tions to "light the fuse". 



While definite experimental evidence is lacking with respect to grouse there is every prob- 

 ability of a direct correlation between such outbreaks and population density. The source of 

 diseases of this kind is not to be found in "unwholesome vapours" but in some other indi- 

 vidual which has become infected. Thus the more frequent the contact of such individuals with 

 their neighbors the greater the opportunity for spreading the ailment. This principle is 

 easily demonstrated in the case of stock held on game farms. It is also believed to be a para- 

 mount factor in connection with the violent fluctuations of the snowshoe rabbit and man) 

 mice. In managing the grouse moors of Scotland it is regarded as sufficiently important 

 that, if the owner and his guests do not take enough birds, the keeper subsequently reduces 

 them to the desired level. Furthermore, the rapid transmission possible among a population 

 at times of high density often steps up the virulence of the causative organism. 



Dissipation of excessive concentrations is a means of guarding against such consequences. 

 Therefore, harvesting the surplus each fall, by hunting, is a practical management measure. 



