Ornate box turtles nest chiefly in June. Some females nest as early as
the first week of May or as late as mid-July but the nesting season
reaches its peak in mid-June. Eggs nearly ready to be laid were in
oviducts (determined by bimanual palpation in the field or by
dissection in the laboratory) of many females captured in June; nearly
half of the records so obtained were in the second week of that month.
Early records of shelled oviducal eggs were April 25 (specimen from
Ottawa County, Oklahoma), May 5, and May 22. The two latest records
are for females retaining oviducal eggs on July 2 and 11. Known dates
for nesting of free-living females were distributed rather evenly
through the month of June. It is worthy of note that all (four) of
the nestings known to occur in July were by captive females. Females
of _T. ornata_, like those of some other turtles (Cagle and Tihen,
1948; Risley, 1933:694), seem to retain their eggs until conditions
are suitable for nesting. Most of the reports in the literature of
nesting after mid-July represent records for captive females.
Nests of _T. o. ornata_ were so well-concealed that they were
difficult to find even when a gravid female had been followed to the
approximate location by means of a trailing thread. Females spend one
to several days seeking a site for the nest, usually traveling a
circuitous route within a restricted area. Movements of nest-seeking
females were more extensive than those of males and non-gravid females
observed in the same periods.
Activities of one gravid female, typical in most respects of the
activities of several other gravid females observed (for periods of
one to 23 days) at the Damm Farm, illustrate pre-nesting behavior
(Fig. 29). A trailer was attached to the female on the morning of June
7. She was recovered early on the following afternoon; her movements
in the elapsed period had been restricted to a small, deep, ravine 150
feet long and 20 to 30 feet wide. She had traversed each edge of the
ravine at least once and had crossed it six or seven times, keeping
mostly to areas on the upper parts of south--or west--facing slopes
where vegetation was sparse or lacking. In six places she had dug into
the ground, probably to test the suitability of the soil for nesting.
In three places she dug beneath rocks that jutted out from the bank,
and in two places merely scratched away the upper crust of soil. Her
most recent attempt at digging (probably late the previous evening or
in early morning on the day of her capture) consisted of a
flask-shaped cavity that, but for the lack of eggs and a covering of
earth, was like a completed nest (Pl. 21, Fig. 1). The cavity was 55
millimeters deep, 80 millimeters wide at the bottom, and 60
millimeters wide at the opening. For several inches about the opening
the earth was slightly damp. That piled on the rim of the opening was
of the consistency of thick mud, indicating that the female had voided
fluid first on the surface of the earth and again inside the cavity to
soften the soil. Subsequently during eight days her activities were
similar but not so extensive as on the day described above. It was
determined by daily palpation that she laid her eggs somewhere in the
general area of the ravine on June 15 but the nest could not be found.
No completed nests containing eggs were discovered at the Damm Farm
but the locations of several robbed nests and partly completed nests
provided some information on preferred sites. The nests found were on
bare, well-drained, sloping areas and were protected from erosion by
upslope clumps of sod or rocks. The nest cavity illustrated in Plate
21 was at the edge of the sod-line on the upper lip of the west-facing
bank of a ravine. One nest had been excavated in a shallow den beneath
an overhanging limestone rock. Three nests were on west- or
south-facing slopes and one was on the north-facing bank of a ravine.
Box turtles presumably select bare areas for nesting because of the
greater ease of digging. One female at the Damm Farm was thought to
have laid her eggs in a cultivated field and William R. Brecheisen
told me he discovered two nests in a wheat field being plowed in July,
1955.
The repeated excavation of trial nest cavities presumably exhausts the
supply of liquid in the female's bladder. Frequent imbibing of water
is probably necessary if the search for a nesting site is continued
for more than a day or two. Standing water was usually available in
ponds, ravines, ditches, and other low areas at the Damm Farm in June.
Nesting in June, therefore, is advantageous not only because of the
greater length of time provided for incubation and hatching but also
because of the amount of water available for drinking. Females can
probably be more selective in the choice of a nesting site if their
explorations are not limited by lack of water.
Females of _T. ornata_, in all instances known to me, began excavation
of their nests in early evening and laid their eggs after dark; Allard
(1935:328) reported the same behavior for _T. carolina_.
William R. Brecheisen, on July 22, 1955, at his farm, two miles south
and one mile west of Welda, Anderson County, Kansas, observed that a
large female began digging a nest in an earth-filled stock tank at
6:00 P. M. At first she moved her body about on the surface of the
earth, loosening it and pushing it aside with all four legs, making a
depression approximately two inches deep and large enough to
accommodate her body. At 7:30 P. M. she began digging alternately with
her hind feet at the bottom of the depression. Digging continued until
10:00 P. M., at which time the nest cavity was three inches deep, and
three inches in diameter, with a smaller opening at the top. Six eggs
were laid in the next half-hour. Covering of the nest probably took
more than one hour but observations were terminated after the final
egg was laid. By the following morning the nest-site had been
completely covered and was no different in appearance from the rest of
the earthen floor of the tank. (Brecheisen observed more of the
nesting than anyone else has recorded and I am obliged to him for
permission to abstract, as per the above paragraph, the notes that he
wrote on the matter.)
A nest made by a captive female at the Reservation was of normal
proportions except for an accessory cavity that opened from the neck
of the nest, immediately below the surface of the ground. This smaller
cavity contained a single egg. This peculiar nest may have resulted
from the efforts of two different females since several were kept in
the same outdoor pen.
Ten adult females were kept in an outdoor cage in the summer of 1955.
The cage was raised off the ground on stilts and its floor was covered
with 12 inches of black, loamy soil. A small pan of water was always
available in the cage and the turtles were fed greens, fruit, and
table scraps each evening. Nesting activity was first noted on June
21, when one of the females was digging a hole in a corner of the
enclosure. She dug with alternate strokes of her fully-extended hind
legs in the manner described (Legler, 1954:141) for painted turtles
(_Chrysemys picta bellii_). Nevertheless, digging was much less
efficient than in _Chrysemys_, because of the narrow hind foot of the
female _T. ornata_; approximately half of the earth removed by any one
stroke rolled back into the nest or was pulled back when she
reinserted her leg. The female stopped digging when I made sudden
movements or held my hand in front of her. Digging continued for
approximately 45 minutes; then the female moved away and burrowed
elsewhere in the cage. The nest cavity that she left was little more
than a shallow depression. Three other females were digging nests
early in the evening on July 3, 5, and 8; in each of these instances
the female stopped digging to eat when food was placed in the cage and
completed the nesting process, unobserved, later in the evening. In
each instance where nest-digging by captive females was observed, the
hind quarters of the female rested in a preliminary, shallow
depression, and the anterior end of the body was tilted upward at an
angle of 20 to 30 degrees. In late June and early July several eggs
were found, unburied, on the floor of the cage and in the pan of
water.
The excavation of a preliminary cavity by captive females may not
represent a natural phenomenon. Allard (1935) made no mention of it in
his meticulous description of the nesting process in _T. carolina_. It
is worthy of mention, however, that Booth (1958:261) reported the
digging of a preliminary cavity by a captive individual of _Gopherus
agassizi_.