Arizona 1 
Exp. Sta ; 
LIFE HISTORY OF THE KANGAROO RAT. 
11 
are at some time of day very active. The worn paths become 
most conspicuous in the autumnal harvest season, when they stand 
out in strong contrast to surrounding grass. One usually finds not 
far distant from the main habitation one or more smaller burrows, 
each with from one to three typical openings, connected by the trail 
or runway system with the central den, and these we have called 
"subsidiary burrows" (PI. VI. Fig. 2). These will be again 
referred to in discussing the detailed plan of the entire shelter 
system. 
Examination of the runways and of the denuded area about a 
mound discloses an abundance of almost indecipherable tracks. The 
dust or sand is ordinarily much too dry and shifting to record clear 
footprints, and there are no opportunities to see footprints of this 
species recorded in good impressionable soil. Very characteristic 
traces of kangaroo rats may be readily observed in the dust about the 
mounds, however, and these are long, narrow, sometimes curving, 
furrows made by the long tails as the animals whisk about their work 
or play. 
Signals. 
If a scratching or tapping sound be made at the mouth of a bur- 
row, even in the daytime, one is likely to hear a muffled tapping in 
response, and this may at times be heard while one is engaged in 
excavating a mound. It has a chirring or fluttering quality, de- 
scribed by Fisher as resembling the noise of a quail flying. Bailey 
(1905, 148) is of the opinion that it is used as a signal of alarm, call 
note, or challenge, a view which the present authors believe to be cor- 
rect. During the winter of 1920-21, however, both Bailey and 
Vorhies discovered that this sound, or a very similar one, is made 
by the rapid action of the forefeet in digging. On one occasion 
in the laboratory the sound was given by one of a pair and was 
responded to at once by the other, the two being in separate but con- 
tiguous cages. This observation, however, could not be repeated. 
(Vorhies MS.) 
One evening, while working in the vicinity of the Burro Moun- 
tains, N. Mex.. Goldman heard a kangaroo rat near camp making 
this thumping noise. Taking a lantern, he approached the den, very 
cautiously, until within 10 feet. The kangaroo rat was just outside 
the entrance of one of its burrows, and though moving about more or 
less restlessly at first showed little fear, and kept up the thumping 
or drumming at intervals. When making the noise the animal was 
standing with the forefeet on the ground and the tail lying extended. 
The noise seemed to be made with the hind feet only, and the vibra- 
tion of the feet could be seen. The tapping was kept up for a second 
or two at a time, the sounds coming close together and being repeated 
