CHANGES FOR ADAPTATION IN THE MOLE 341 
order to gain some idea of the force exerted by the fore legs, I 
wrapped a captured mole in a strong cotton cloth. With one or 
two efforts of its powerful paws it tore the cloth and emerged. 
If one attempt to tear the cloth in a similar manner with his 
fingers he realizes that this small animal can do easily what is 
almost an impossible task for man. 
The depth of the tunnels depends largely on the condition of 
the ground. They may be as deep as 2 feet. Sometimes, in 
making these deep burrows through soil that is too compact to 
be easily pushed aside, the mole brings the dirt to the surface 
and deposits it in mounds. 
The diameter of the runways is from 2 to 23 inches. The 
main burrows are always larger than the side branches which 
lead to the feeding grounds. The main burrows are also perma- 
nent, and the mole repairs any damage which they may sustain. 
The length of new burrows which a mole may make during a 
single night varies with the condition of the soil. After a rain, 
which renders the soil more moist and less compact, moles are 
more active in making new burrows. lLydekker (’93) records 
the formation of a new burrow about 100 yards long during a 
single night. He estimates that if a man were to perform an 
equivalent amount of work during the same time he would have 
to excavate a tunnel 37 miles long and sufficiently large to easily 
permit the passage of his body. 
The rate of locomotion of the mole through its burrow has 
been variously stated as fast, but the distance traveled in a 
given time has, so far as I can find, not been estimated. The 
nearest approach to a definite determination of the rate which I 
have seen was by Le Court (’88). He stuck straws down into 
the burrows at intervals leaving a portion of each extending 
above the ground. As the mole progressed along the burrow 
these straws were moved and the rate could be determined by 
observing the straws. But instead of giving a rate which could 
have been so easily calculated, he concludes that ‘‘the speed 
of the frightened mole was equal to that of a horse at full trot.’’» 
This does not seem possible when one considers the bulky fore 
legs which are modified for strength and not speed. 
