Arizoua \ 

 Exp. Sta. / 



LIFE HISTORY OF THE KANGAROO RAT, 



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 system in the dens, it was considered advisable to map them with 



Pig. 2. — Diagram of a typical den of Dipodomijs 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 ; 8, storage ; OSj old storage ; r, 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. 



