One traveling over territory thickly occupied by the banner-tailed
kangaroo rat is certain to note the numerous and conspicuous mounds so
characteristic of the species, particularly if the region is of the
savannah type, grassy rather than brushy. These low, rounded mounds
occupy an area of several feet in diameter, and rise to varying heights
above the general surface of the surrounding soil, the height depending
rather more upon the character of the soil and the location of the mound
as to exposure or protection than upon the area occupied by the burrow
system which lies within and is the reason for the mound.
A den in sandy soil in the open may be of maximum size in area occupied
and yet scarcely present the appearance of a mound in any sense, due
probably both to the fact that the sandy soil will not heap up to such a
height over a honeycomb of tunnels as will a firmer or rocky soil, and
also to its greater exposure to the leveling action of rains and the
trampling of animals. These mounds are in themselves large enough to
attract some attention, but their conspicuousness is enhanced by the
fact that they are more or less completely denuded of vegetation and are
the centers of cleared areas often as much as 30 feet in diameter (Pl.
V, Fig. 1); and further that from 3 to 12 large dark openings loom up in
every mound. The larger openings are of such size as to suggest the
presence of a much larger animal than actually inhabits the mound. Add
to the above the fact that the traveler by day never sees the mound
builder, and we have the chief reasons why curiosity is so often aroused
by these habitations.
On the Range Reserve the mounds are usually rendered conspicuous by the
absence of small vegetation, but Nelson writes that in the vicinity of
Gallego, Chihuahua, they can be readily distinguished at a distance
because of a growth of weeds and small bushes over their summits, which
overtop the grass. In the vicinity of Albuquerque, N. Mex., Bailey
reports (and this was recently confirmed by Vorhies) that the mounds
about the holes of _spectabilis_ are often hardly noticeable. Hollister
writes that in the yellow-pine forests of the Gallina Mountains the
burrows are usually under the trunk of some fallen pine, both sides of
it in some cases being taken up with holes, there being some eight or
ten entrances along each side, the burrows extending into the ground
beneath the log. In the vicinity of Blanco, N. Mex., Birdseye says that
occasionally _spectabilis_ makes typical dens but more often lives in
old prairie-dog holes (_Cynomys_), or in holes which look more like
those of _D. ordii_.