Arizona { 
Exp. Sta. / 
LIFE HISTORY OF THE KANGAROO RAT. 
5 
Key to Species of Dipodomys in Arizona. 
a\ Size much larger (hind foot and greatest length of skull more than 4'2 
millimeters) ; tail tipped with white. 
ft 1 . Upper parts dark brownish buffy : tail dark brownish <»r blackish 
with more sharply contrasted white tip; interparietal broader, 
distinctly separating mastoids (range in Arizona mainly south- 
eastern part) Dipodomys spectabilis. 
b. 2 Upper parts light ochraceous-buffy : tail pale brownish with less 
sharply contrasted white tip : interparietal narrower, reduced to 
mere spicule between mastoids (range in Arizona mainly south- 
western part) Dipodomys deserti. 
a 2 . Size much smaller (hind foot and greatest length of skull less than 
42 millimeters) : tail not tipped with white. 
6\ Hind foot with four toes Dipodomys merriami. 
I) 2 . Hind foot with rive toes Dipodomys ordii. 
On account of the small size, ?nema??ii and ordii do not require 
detailed color comparison with the other two. The general color of 
the upperparts of spectabilis is much darker than that of deserti; 
whereas spectabilis is ochraceous-buff or light ochraceous-buff griz- 
zled with blackish, deserti is near pale ochraceous-buff and lacks the 
blackish. 
The color of the upperparts alone amply suffices to distinguish 
spectabilis and deserti; but the different coloration of the tail is the 
most obvious diagnostic feature. The near black of the middle por- 
tion of the tail, the conspicuous white side stripes, and the pure 
white tip make the tail of spectabilis stand in rather vivid contrast 
to the pale-brown and whitish tail of deserti. 
The dens of the two larger species of Dipodomys — spectabilis and 
deserti — can be distinguished at a glance from those of the two 
smaller — merriami and ordii — by the fact that the mounds of the 
former are usually of considerable size and the burrow mouths are 
of greater diameter. On the Range Reserve merriami erects no 
mounds, but excavates its burrows in the open or at the base of 
Prosopis, Lycium, or other brush. The mounds of spectabilis are 
higher than those of deserti, the entrances are larger, and they are 
located in harder soil (PI. Ill, Fig. 1). The den- of deserti are 
usually more extensive in surface area than those of spectabilis, and 
have a greater number of openings (PI. Ill, Fig. 2). 
DESCRIPTION. 
GENERAL CHARACTERS. 
Size large: ears moderate, ear from crown (taken in dry skin) 9 
or 10 millimeters; eyes prominent; whiskers long and sensitive: fore 
feet short and weak; hind feet long and powerful, provided with 
four well-developed toes; tail very long, usually 30 to 40 per cent 
107600—22 2 
