142 ANIMAL LIFE IN THE YO SEMITE 



cultivating the soil. The pocket gopher is wonderfully equipped to handle 

 the refractory young soils of the semi-arid Sierran slopes, and his is the 

 role here of Darwin's earthworm in England. 



Now that the greatest of all agencies of erosion, the glaciers, so stressed 

 by John Muir, have almost ceased to operate, the less obvious agencies 

 stand ready to claim their due prominence, if we will but look for them. 

 The element of time granted, we are able to conceive of vast accomplish- 

 ments on the part of even so humble a contributor as the pocket gopher. 



A real service, it seems to us, performed by burrowing animals, among 

 which in the Sierras the pocket gopher stands foremost, is that of counter- 

 acting the packing effect of large mammals on uncultivated pasture lands. 

 The impact of heavy feet on the soil, especially when wet, crowds the 

 particles together and renders the earth less suitable for plant growth. 

 Close tamping tends to exclude air and hence to suffocate the plant roots, 

 to which oxygen is as essential as it is to animal life. One has but to 

 observe the condition of mountain meadows outside the limits of National 

 Parks, to appreciate the point here made. Often where the country has 

 been overstocked with cattle or domestic sheep, the grasslands have become 

 poor — the crop of grass is scrawny- — except where gopher workings occur ; 

 the sites of these are marked by patches of vivid green. Indeed, on 

 ordinary hill slopes within the Yosemite section we have repeatedly noted 

 the rejuvenation of the plant cover here and there due directly and 

 obviously to the activity of the gophers. Before the advent of the white 

 man with his cattle and horses a similar service was rendered, though in 

 lesser degree, perhaps, when the wild deer, mountain sheep, and bears 

 frequented the same meadows. 



The pocket gophers, then, are the chief natural cultivators of the soil, 

 and upon their continued activity the maximum thrift of wild vegetation is 

 dependent. 



The question of damage by gophers to forests under natural conditions, 

 for example, injury to young trees, has been raised by foresters. There is 

 no doubt that gophers do girdle or cut off the stems of many seedlings 

 and thus terminate the existence of numerous individual trees. But the 

 great number of seedlings observable on parts of any forest floor, vastly 

 more than could ever reach maturity, would seem to indicate that an adjust- 

 ment in this direction had been reached long ages ago. Plants in general 

 provide for a rate of replacement sufficient to meet the maximum prob- 

 abilities of casualty, this involving all stages from the seed to the mature 

 fruiting plant. 



In the arable lowlands of California the pocket gopher is well-nigh 

 universally condemned for pursuing his normal activities, while making 

 his living, on lands that have been appropriated and cultivated by man. 



