Life History of the Kangaroo Rat | Page 7

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.
[Illustration: PLATE V. FIG. 1.--CLEARING ABOUT A MOUND.
A typical clearing about a mound of Dipodomys s. spectabilis, showing
the autumnal denudation of the mound and surrounding areas. In this
instance about 30 feet in diameter.]
[Illustration: PLATE V. FIG. 2.--MOUND AND RUNWAYS.
A small mound of Dipodomys s. spectabilis in early autumn, showing
runways radiating from the den. Evidences of activity may be noted in
and about the surface of the mound.]
[Illustration: PLATE VI. FIG. 1.--RUNWAY OF DIPODOMYS S.
SPECTABILIS.
Well-traveled path leading from the main den, in the foreground, to a
subsidiary burrow (see Fig. 2, below), about 30 feet distant, at apparent
end of runway.]
[Illustration: PLATE VI. FIG. 2.--SUBSIDIARY BURROW OF

DIPODOMYS S. SPECTABILIS.
Located at the end of the 30-foot runway shown in Figure 1, above.
This has three openings, two in the foreground and the third a little to
the rear and indicated by an arrow.]
SIGNALS.
If a scratching or tapping sound be made at the mouth of a burrow,
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, described 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 correct. 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 contiguous cages. This observation, however, could not
be repeated. (Vorhies MS.)
One evening, while working in the vicinity of the Burro Mountains, 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 vibration 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 rhythmically after a very short
interval, suggesting the distant galloping of a horse. After continuing in
this way for a short time, the animal turned quickly about, with its head
in the opposite direction, and began tapping. It appeared to pay little
attention to the light, but finally gave a sudden bound and entered one
of its holes about 4 feet from the one in front of which it had been

standing.
Vorhies has repeatedly noted when watching for the appearance of a
kangaroo rat at night that this sound invariably precedes the rodent's
first emergence into the open, and often its appearance after an alarm,
though when the storage season has begun and the kangaroo rat is
carrying loads of grass heads or other material into its den, it regularly
comes out without preliminary signaling. Vorhies has also observed it
making the sound while on top of the mound, and certainly not digging,
but was unable to see how it was made.
VOICE.
No data concerning any call notes or sounds other than those described
above are at hand, with the following exception: Price (in Allen, 1895,
213), who studied the habits of the animal in the moonlight, at Willcox,
Ariz., says that a low chuckle was uttered at intervals; and Vorhies has
had one captive female that would repeatedly utter a similar chuckle in
a peevish manner when disturbed by day, and one captive male which,
when teased into a state of anger and excitement, would squeal much
like a cornered house rat. Vorhies has spent many moonlight hours
observing kangaroo rats, but without ever hearing a vocal sound uttered
by free individuals.
DAILY AND SEASONAL ACTIVITY.
The kangaroo rat is strictly nocturnal. An observer watching patiently
by a den in the evening for the animal's first appearance is not rewarded
until darkness