116 ANIMAL COMPETITORS 
way. His movement in digging often seems as 
rapid and automatic as that of a shuttle. 
Except in times of deep frost, the burrows 
are seldom more than a foot underground, and 
generally about six inches. At intervals, often 
within a few feet, the gopher comes to the sur- 
face to throw up a little hill of dirt; but the 
opening which he makes is closed by being 
DIAGRAM OF A GOPHER’S BURROWING. 
packed so full of dirt that no trace of the tunnel 
is visible except the little mound. 
The gopher goes on digging in winter as 
well as in summer; but if the frost prevents him 
from coming to the surface, he uses a cross 
section of his tunnel into which to pack the 
earth which he has dug for his new excavations. 
These tightly packed cylinders of earth are 
often turned up by the plow. 
Pocket-gophers apparently breed only once a 
