The known range of _T. ornata_ includes the southern half of the
Grassland Biome, part of the Desert Biome, and that part of the
Temperate Deciduous Forest Biome known as the Prairie-Forest Ecotone.
The species is found in microhabitats that differ widely in food
supply, temperature, moisture, and kind of soil. In spite of its
relatively high degree of morphological specialization, _T. ornata_ is
remarkably versatile in regard to habitat requirements.
Ornate box turtles are relatively inconspicuous in natural
surroundings and collectors seldom seek out and obtain specimens under
completely natural conditions as may be done with certain other
reptiles and amphibians by turning rocks, tearing apart logs, or
setting traps. Most series of specimens are obtained by hunting after
rains on roads or other natural breaks in vegetational cover. Detailed
information on habitat preferences is lacking.
Low temperature seems to be an important factor limiting the
distribution of _T. ornata_ in the northern part of its range. Box
turtles, like nearly all other reptiles occurring at these latitudes,
spend the winter in underground hibernacula. The depth to which the
ground freezes in the coldest part of the winter is therefore a
critical factor. The ground freezes to an average depth of 30 inches
or less over most of the range of the species; only in the extreme
northern part of the range (southern South Dakota, southeastern
Wyoming) does the ground freeze to an average depth of as much as 35
inches. Average depth of freezing is, in fact, less than 15 inches
over more than one half the range of the species. The average number
of frost-free days per year ranges from 130 to 140 days in the
northern part of the range to more than 250 days in the southwestern
part of the range.
_Terrapene ornata_ occurs from near sea level to elevations of more
than 5000 feet. Both subspecies are found at both high and low
elevations but _luteola_ is more consistently taken at high elevations
than _ornata_. The latter subspecies commonly occurs at elevations
above 4000 feet on the high plains in extreme western Kansas and
eastern Colorado; the highest elevation from which I have examined
specimens of _T. o. ornata_ is between 4600 and 4700 feet near Akron,
Washington County, Colorado. The greater part of the known range of
_T. o. luteola_ lies above 3000 feet.
Norris and Zweifel (1950:1) observed _T. o. luteola_ on the Jornada
del Muerto, an elongate plain approximately 4500 feet high, in
southeastern Socorro County, New Mexico; box turtles were abundant on
the level part of the plain and on the bordering foothills but not at
higher elevations where the substratum was rocky. The authors
otherwise noted no preference for any kind of soil. The principal
elements of the plant associations in which the turtles were found
were creosote bush, yucca, mesquite, juniper, tarbush, and grasses.
Lewis (1950:3) reported that _T. ornata luteola_ inhabited the
yucca-grassland zone in Dona Ana County, New Mexico; he stated (_op.
cit._: 10) that individuals were commonly found on roads after rains
and in cloudy weather. No specimens were taken at altitudes higher
than 4300 feet.
I have examined specimens of _luteola_ from elevations of
approximately 5500 feet in Cochise County, Arizona, and Lincoln
County, New Mexico. These localities are probably at or near the
maximum elevation at which the species occurs. The texture of the
substrate is the most important factor limiting vertical distribution.
Ornate box turtles, like nearly all other turtles, excavate nests; _T.
ornata_ is a burrower, at least for purposes of hibernation.
Populations of the species, therefore, could not survive in areas of
hard unyielding substrata. Such substrata seem to be the most
important factor limiting altitudinal distribution.
Most of the area in which _T. ornata_ occurs is semiarid or arid.
Average precipitation in the warm season (April through September)
varies from approximately 25 inches in the northeast to less than ten
inches in the southwest. In drier parts of the range, precipitation is
unevenly distributed over the warm season. Long, hot, dry periods are
unfavorable for reptilian activity. _T. ornata_, like many other
reptiles inhabiting dry regions, survives long periods without water
by seeking shelter (usually underground) and remaining quiescent.
Populations of the subspecies _luteola_ live under far more rigorous
conditions in this respect than do the more northern populations.
Specimens of _luteola_ from Arizona that were kept for several years
in the laboratory under dry conditions and fed adequately, but at
infrequent intervals, were able to remain healthy and even to grow
whereas examples of _ornata_ kept under the same conditions soon
languished and died; _luteola_ seems to be physiologically adapted for
existence under arid conditions, where normal activity is sometimes
possible for only a few weeks in the year.
The prairies of Nebraska, Kansas, Oklahoma, and northern Texas seem to
provide the most nearly optimum habitat for the species; in these
regions box turtles are active on a large majority of the days from
April to October in years having average or better than average
precipitation and population density seems to be greater than in the
more arid parts of the range.
Activities of man have probably affected the density of populations of
the ornate box turtle in many parts of its range but appear not to
have acted as limiting factors except in certain areas along the
northern edge of the range (Blanchard, 1923:19-20, 24) where
disruption of grassland through intensive cultivation probably has
excluded the species. Unlike certain other reptiles of the Great
Plains (Fitch, 1955:64), _T. ornata_ seems not to have been
affected--either by direct decimation of populations or by disruption
of habitat--by intensive zoological collecting in restricted areas.
Environmental changes such as those resulting from overgrazing and
erosion, or from protection of the habitat from grazing could be
expected to cause long-term changes in populations of ornate box
turtles.
_Terrapene o. ornata_ is an omnivorous, opportunistic feeder,
primarily insectivorous but able to subsist on nearly any sort of
animal or vegetable food. The general food habits of _luteola_ are
poorly known but probably resemble those of _ornata_. Although kind of
food available probably does not limit the distribution of _T. ornata_
there are indications that it influences population density. In
Kansas, for example, dung insects are an important staple in the diet
and box turtles were found always to be more numerous in areas where
domestic cattle provided an abundant supply of dung than elsewhere. A
similar relationship probably existed in former times between box
turtles and native ungulates. Near extinction of buffalo in the Great
Plains possibly caused a decrease in populations of box turtles. Henry
S. Fitch told me that the number of _T. ornata_ at the Reservation
gradually declined after cattle were removed from the area in 1948.
In summary, the distribution of _T. ornata_ seems to be limited by: 1)
Presence of a substrate too hard to permit digging of nests and forms
(southwestern and western edges of range); 2) temperatures causing the
ground to freeze deep enough (approximately 30 inches) to kill turtles
in hibernacula (northern edge of range); and, 3) the lack of one or
more relatively wet periods in the course of the warm season,
preventing at least temporary emergence from quiescence (southwestern
edge of range).