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.