HABITS OF THE GREAT SOUTHERN TORTOISE. 



39 



begin the burrow, tbey endeavor at once to penetrate downward 

 to the level in which they obtain their food. At the outset they 

 manage, by frequently backing out of the passage, and thrust- 

 ing the earth behind them in their retreat, to clear a considerable 

 opening. When they have advanced a few feet in the excavation, 

 they cease to discharge the material excavated in their advance, 

 but thrust it behind them, and leave it lying in the chamber, 

 which it entirely closes. With this storage-room provided, the 

 gophers are able to advance through the earth for the distance of 

 some yards ; but as the earth compacted by its own weight, by the 

 pressure exercised through the expansion of roots, and the action' 

 of the rain, occupies less space than the same material loosened 

 in the progress of the burrow, they soon become hamj^ered in 

 their movements. They then turn toward the surface and con- 

 tinue the excavation upward until they have attained very 

 nearly to the open air. They then use the great strength which 

 they clearly possess to thrust a quantity of the burrowed material 

 upward until it rises above the surface in the form of a cone, 

 and by the space in the burrow thereby gained they are able to 

 go a few feet further in their tortuous line of advance, when they 

 must again seek to discharge a portion of the earth in the man- 

 ner just described. So the creature proceeds in its devious under- 

 ground way, coming near the surface and pushing out a portion 

 of the sand at intervals of from two to five feet in its path. 

 In this manner it appears to journey at times for a distance of 

 hundreds of feet before it again has occasion to come to the 

 open air. 



For the greater portion of its journey, the path of this creat- 

 ure seems to lie within two or three feet of the surface, that 

 being the level in which it finds the roots which afford it food. 

 It appears, however, from the points at which they emerge in the 

 railway-cuts, not unlikely that they occasionally penetrate to the 

 depth of six feet below the top of the soil. Although they plen- 

 tifully occur throughout a region having a superficial area of 

 nearly one hundred thousand square miles, they appear to exercise 

 a considerable choice as to the ground they inhabit. They de- 

 mand, in the first place, that the water-level shall not be within a 

 dozen feet of the surface, and that the material they traverse 

 shall be a very open-textured sand. This is probably because in 

 the rainy season any considerable rise in the level of the ground- 

 water would be destructive to them ; unless they could quickly 

 escape from their burrows, they would be drowned. It is often 

 possible, through this habit, to determine in an approximate way 

 the depth of the Tertiary beds of clay and other indurated ma- 

 terials which at many points lie near the top of the sand which 

 envelop the surface in the Southern States. Where these beds. 



