NORTH AMERICA AND THE WEST INDIES 357 



whereas with a light crust the coyotes are able to give pursuit 

 effectively. Another danger that has developed is the intro- 

 duction of scab by the grazing of domestic sheep on the upper 

 ranges in summer, in the States where bighorn occur. Warren 

 was told of an instance in which 75 bighorns were found dead 

 from this cause in the West Elk Mountains. More recently 

 the bighorn in Glacier Park have in some instances shown the 

 development of a fatal pneumonia, to the extent in one case 

 that 15 out of a band of a hundred had died. The primary 

 trouble seems due to a lungworm, which opens the way for 

 secondary bacterial infection. Most of this seemed to occur 

 among bighorns that in a certain locality were fed with hay, 

 where local pasturage had been overgrazed. Other cases of 

 young lambs dying of pneumonia due to infection by Pasteu- 

 rella, without primary infection by the lungworms, were also 

 found. No suggestions for eradicating this danger have so far 

 been made. The lungworms probably pass one stage in a 

 snail and then, if the small snails are eaten by the sheep while 

 grazing, the parasite continues its development in the new 

 host, and invades the lung tissue (see Marsh, 1938). * The late 

 George Bird Grinnell (1928) wrote that "many years ago Col. 

 Edward L. Munson expressed the belief that an epidemic of 

 anthrax communicated to them from domestic sheep feeding 

 on the plains below had exterminated the wild sheep of the 

 Bear Paw Mountains in Montana." They were formerly 

 common there, but in later years none has been found. Thus 

 it seems likely that bighorn may be susceptible to various 

 introduced diseases that are brought in by domestic sheep and 

 against which they may need in some way to be guarded. 



As a preliminary to more intelligent management and pro- 

 tection of this species, H. B. Mills (1937) has made an intensive 

 study of the bighorn population of the Yellowstone National 

 Park in the northwestern corner of Wyoming and the adjacent 

 edge of Idaho. Here, notwithstanding Vernon Bailey's earlier 

 estimate that the area might easily support ten times the 

 present population, the number of bighorns has remained 

 about 200 for the past 20 years or more and even dropped to 

 about half that number as from 1927-33. Thus under protec- 

 tion from both man and natural predators, the animals show 

 a decrease. A careful census of the bighorns in the park in 

 1934-35 gave a total of 240. They keep more or less in groups, 



