Life History of the Kangaroo Rat | Page 9

present were obviously young animals.
SENSE DEVELOPMENTS.
Without making special investigations through a study of behavior or
other special methods, one can speak in only general terms regarding
what appear to be the special sense developments of kangaroo rats. The
eyes are large, as is very often the case in nocturnal animals, and when
brought out into the bright light of day the rats perhaps do not see well.
Yet, if an animal leaves a den which is in process of excavation, and
follows one runway, even in bright sunlight, it makes excellent speed to
the next opening, often a distance of several yards. Whether this is
accomplished chiefly by the aid of sight or in large measure by a
maze-following ability, such as experiments have shown some rodents

to have, can not be stated without precise experimentation. Marked
ability to follow a maze would not be at all surprising in view of the
labyrinthine character of the underground passages which make up the
normal habitation.
When watching beside a mound by moonlight one is impressed with
the fact that the rats possess either a very keen sense of hearing or of
sight, probably both. The very slightest movement or noise on the part
of the observer results, with a timid individual, in an instantaneous leap
for safety, a disappearance into the burrow so sudden as to be almost
startling. All attempts to obtain flashlight photographs at the mounds
were failures, the animal either having gotten completely out of the
field before the light flashed following the pull of the trigger, or leaving
merely an indistinguishable blur on the plate as it went, and this in spite
of carefully hiding the trigger chain behind a screen. A slight noise
accompanying the trigger action gave the alarm in one case, and in
another the length of time of the flash was sufficient for the get-away.
The marvelous quickness of the animal clearly indicates a remarkably
short reaction time. Occasionally a bold individual is found, as in the
case of one which came out repeatedly, even after being flashed twice
in the same night.
Certain peculiar physical characteristics suggest a relationship to sense
reactions. On these, however, the authors are not prepared to do more
than offer suggestions for future work. The extremely large mastoids
found in kangaroo rats suggest a connection in some way with special
developments of the sense of hearing or of balance. It may be noted
that an intermediate condition between the kangaroo rats and the
majority of rodents in respect to this character is to be found in the
pocket mice (Perognathus), which belong to the same family. Herein
lies a field for some interesting experimentation and discovery.
The small, pointed nose might suggest a not overkeen sense of smell,
and there appears no reason to believe that this sense is particularly
well developed. However, the turbinals are very complex. The vibrissæ
are long and sensitive, and may indicate a special development of the
sense of touch as an adaptation to nocturnal habits and to life in an

underground labyrinth. The long, well-haired tail doubtless serves as an
important tactile organ as well as a balance.
MOVEMENTS AND ATTITUDES.
Movements and attitudes are characteristic. As a kangaroo rat emerges
from the burrow a reason for the relatively large size of the opening is
seen in the fact that, kangaroolike, the animal maintains a partially
upright position. Its ordinary mode of progression is hopping along on
the large hind legs, or, when in the open and going at speed, leaping.
When moving slowly about over the mound, as if searching for food, it
uses the fore legs in a kind of creeping movement. It appears to be
creeping when pocketing grain strewn about, but close observation
shows that the fore feet are then used for sweeping material into the
pockets, reminding one somewhat of a vacuum cleaner. When it
assumes a partially upright position the fore limbs are usually drawn up
so closely that they can be seen only by looking upward from a
somewhat lower level than that occupied by the animal. The slower
movements of searching or playing about the mound are occasionally
interrupted by a sudden leap directly upward to a height of 1-1/2 to 2
feet, often with no apparent reason other than play. This is, however, a
fighting or guarding movement, though indulged in for play. The play
instinct seems to be well developed, and in evidence on any moonlight
night when actual harvesting operations are not going on.
STORING HABITS.
Probably no instinct is of greater importance to the kangaroo rat than
that of storing food supplies. When a crop of desirable seeds is
maturing the animal's activities appear to be concentrated on this work.
During September, 1919, when a good crop of grass