Arizona \ 
Exp. Sta. / 
LIFE HISTOEY OF THE KANGAROO EAT. 
29 
a single opening closed. Further, night observations disclose that 
the inhabitant of the mound will appear from some one of the two 
or three most-used openings when night falls, and not necessarily 
from one which has been closed by day. Recently an opening closed 
one day was observed in use during the night, but was left open 
all the next day. 
In attempting to determine whether there exist similarities of plan 
or s}^stem in the dens, it was considered advisable to map them with 
Fig. 2. — Diagram of a typical den of Dipodomys spectaMlis spectahilis. Double shading 
indicates where one portion of tunnel lies above another and solid black a three-story 
arrangement ; A, B, C, etc., active openings to surface ; figures without arrows, depths 
in centimeters to tunnel roofs ; figures with arrows, tunnel widths in centimeters ; N. 
nest chamber ; S, storage ; OS, old storage ; Y, probably an old nest chamber ; Z, old. un- 
used,, or partially plugged openings. 
some degree of accuracy. This we were enabled to do by laying off 
a square about a given mound, 2| or 3 meters each way. and sub- 
dividing it into a series of small squares of half a meter on each side 
by drawing cross-lines on the surface of the ground over the top of 
the mound. One person then did the digging and exploring of the 
tunnels, as to direction and depth, while the other noted the results on 
coordinate paper (Figs. 2 and 3) ; the proper excavation and map- 
ping of one of these workings occupied from four to eight hours for 
the two. 
