In the Tucson region _spectabilis_ is typically a resident of the Lower
Sonoran Zone. This is perhaps the principal zone inhabited over its
entire range, but the animal is often found in the Upper Sonoran also,
and in the Gallina Mountains of New Mexico Hollister found it invading
the yellow pine Transition where the soil was dry and sandy and the pine
woods of open character. The same observer found it common in grassy and
weed-grown parks among the large junipers, pinyons, and scattering
yellow pines of the Bear Spring Mountains, N. Mex. Bailey calls
attention to the fact that the animal apparently does not inhabit the
lower half of the Lower Sonoran Zone, as it extends neither into the Rio
Grande Valley of Texas nor the Gila Valley of Arizona. In extreme
western Texas it is common at the upper edge of the arid Lower Sonoran
Zone, and in this region does not enter the Upper Sonoran to any extent.
In July, 1914, Goldman found this kangaroo rat common on the plain at
4,600 feet altitude, near Bonita, Graham County, Ariz., and noted a few
as high as 5,000 feet altitude on the warm southwestern slopes of the
Graham Mountains, near Fort Grant. Apparently _spectabilis_ reaches its
upper altitude limit in the Burro Mountains, N. Mex., where Bailey has
found it sparingly on warm slopes up to 5,700 feet, and at the western
base of the Sandia Mountains, east of Albuquerque, N. Mex., where dens
occur at approximately 6,000 feet.
About Tucson it is undoubtedly more common in the somewhat higher
portions of the Lower Sonoran Zone, above the _Covillea_ association,
than elsewhere (Pl. IV, Figs. 1 and 2). A few scattered dens are to be
seen in the _Covillea_ belt, but as one rises to altitudes of 3,500 to
4,000 feet, and the _Covillea_ is replaced by the cat's-claws (_Acacia_
sp. and _Mimosa_ sp.) and scattered mesquite (_Prosopis_), with the
_Opuntia_ becoming less abundant, kangaroo rat mounds come more and more
in evidence. Here is to be found the principal grass growth supporting
the grazing industry, and the presence of a more luxuriant grass flora
is probably an important factor in the greater abundance of kangaroo
rats, both _spectabilis_ and _merriami_. In this generally preferred
environment the desert hackberry (_Celtis pallida_) is one of the most
conspicuous shrubs; clumps of this species are commonly accompanied by
kangaroo rat mounds.
In order to ascertain whether the banner-tailed kangaroo rat has any
marked preference for building its mounds under _Celtis_ or some other
particular plant, all the observable mounds were counted in a strip
about 20 rods wide and approximately 4 miles long, an area of
approximately 160 acres, particular note being taken of the kind of
shrub under which each mound was located. Of 300 mounds in this area, 96
were under _Prosopis_, 95 under _Acacia_, 65 under _Celtis_, 11 under
_Lycium_, 31 in the open, 1 about a "cholla" cactus (_Opuntia
spinosior_), and 1 about a prickly pear (_Opuntia_ sp.). There is
apparently no strongly marked preference for any single species of
plant. While both desert hackberry and the cat's-claws afford a
better protection than mesquite--since cattle more often seek shade
under the latter, and in so doing frequently trample the mounds
severely--it appears that the general protection of a tree or shrub of
some sort is sought by kangaroo rats, rather than the specific
protection of the thickest or thorniest species.
The following records indicate particular habitat preferences of
_spectabilis_ as noted at different points in its range:
Occurs on open bare knolls exposed to winds, also on gravelly
places at lower edge of foothills (Franklin Mountains, Tex., Gaut);
here and there over the barest and hardest of the gravelly mesas
(Bailey, Tex., 1905, 147); on open creosote-bush and giant-cactus
desert (Tucson, Ariz., Vorhies and Taylor); on firm, gravelly, or
even rocky soil on the grassy bajada land along the northwest base
of the mountains, either in the open or under _Celtis_, _Prosopis_,
_Lycium_, _Acacia greggii_, or other brush (Santa Rita Mountains,
Ariz., Vorhies and Taylor); mounds usually thrown up around a bunch
of cactus or mesquite brush (Magdalena, Sonora, Bailey); in heavy
soil (Ajo, Ariz., A. B. Howell); loamy soil (Gunsight, Ariz., A. B.
Howell); in mesa where not too stony (Magdalena, Sonora, Bailey);
grassy plain (Gallego, Chihuahua, Nelson); in open valley and high
open plains (Santa Rosa, N. Mex., Bailey); in grassy and weed-grown
parks among the larger junipers, pinyons, and scattering yellow
pines (Bear Spring Mountains, N. Mex., Hollister); on sand-dune
strip (east side of Pecos River, 15 miles northeast of Roswell, N.
Mex., Bailey); among _Ephedra_ patches (San Juan Valley, N. Mex.,
Birdseye); in open sandy soil along dry wash (Rio Alamosa, N. Mex.,
Goldman); on sides and crests of bare, stony hills (Mesa Jumanes,
N. Mex., Gaut); in open, arid part of the valley and stony mesas
(Carlsbad and Pecos Valley, N. Mex., Bailey); about the edges of
the plains of San Augustine and the foothills of the Datil and
Gallina Mountains, and in the Transition Zone yellow-pine forest of
the Gallina Mountains (Datil region, N. Mex., Hollister); on hard
limy ridges (Monahans, Tex., Cary).
A. Brazier Howell notes that _spectabilis_ occurs in harder soil than
does _deserti_. This observation is confirmed by others, and seems to
afford a conspicuous habitat difference between the two, for _deserti_
is typically an animal of the shifting aeolian sands.
Usually, as on the Range Reserve, the rodents are widely distributed
over a considerable area. Occasionally, as in the vicinity of Rio
Alamosa, N. Mex., as reported by Goldman, they occur only in small
colonies.
[Illustration: PLATE IV. FIG. 1.--RANGE CONDITIONS FAVORING KANGAROO RATS.
View on higher portion of Range Reserve, showing type of country where
_Dipodomys s. spectabilis_ is most abundant. Good growth of grama and
needle grasses in October, following summer growth and before grazing
off by cattle and rodents.]
[Illustration: PLATE IV. FIG. 2.--RANGE CONDITIONS LESS FAVORABLE TO
KANGAROO RATS.
View on lower portion of Range Reserve, where _Dipodomys s. spectabilis_
is less abundant. Vegetation consists principally of _Lycium_, mesquite,
rabbit brush, and cactus, there being very little grass.]