THE GRAY GOPHERS 121 
Tapping trrigation-ditches. Another most 
serious mischief, in regions depending on irri- 
gation, is the destruction of ditch-banks. Some- 
times the animals are forced out of irrigated 
land and take up new quarters in the dry ditch- 
banks, or in course of the regular extension of 
their tunnels a ditch is encountered and the 
bank is followed in search of a crossing-place. 
In either case the burrow is almost sure sooner 
or later to penetrate below the water-line and 
start a leak that cuts out the bank and empties 
the ditch. Altogether, it has been estimated by 
the Biological Survey that the loss due to go- 
phers in the western United States is not less 
than a million dollars a month. 
‘‘No animals,’’ the Survey declares, at the 
same time, ‘‘are more easily controlled on a 
small farm or along ditches than gophers. 
They are readily trapped or poisoned, and once 
cleared out of a field others do not come in at 
once. Their mode of travel, which is princi- 
pally by extending their burrows, is of ne- 
cessity slow; and if occasionally caught or 
poisoned around the edge of fields or along 
ditches, they can be effectually controlled.’’ 
