Natural History of the Ornate Box Turtle, Terrapene ornata ornata Agassiz

by John M. Legler

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.

Eggs

The number of eggs in 23 clutches ranged from two to eight (mean, 4.7 ± 1.37 σs]); clutches of four, five, and six eggs were most common, occurring in 18 (78 per cent) instances. The tendency for large females to lay more eggs than small females ([Fig. 6]) was not so pronounced as that reported by Cagle (1950:38) for Pseudemys scripta. The small size of T. ornata, in comparison with other emyid turtles, seemingly limits the number of eggs that can be accommodated internally. The number of eggs per clutch in T. carolina [2 to 7, average 4.2, Allard (1935:331)], is nearly the same as that of T. ornata.

Fig. 6. The relation of plastral length to number of eggs laid by 21 females of T. o. ornata from eastern Kansas.

Shells of the eggs are translucent and pinkish or yellowish when the eggs are in the oviducts. After several days outside the oviducts the shells become chalky-white and nearly opaque. Eggs incubated in the laboratory retained the pinkish color somewhat longer than elsewhere on their under-surfaces, which were in contact with moist cotton, but eventually even this part of the shell became white. Infertile eggs remained translucent and eventually became dark yellow, never becoming white; they could be distinguished from fertile eggs on the basis of color alone. Shells of infertile eggs became brittle and slimy after several weeks.

The outer layer of the shell of a freshly laid egg is brittle and cracks when the egg is dented. After a few days, when the eggs begin to expand, the shell becomes flexible and has a leathery texture. The shell is finely granulated but appears smooth to the unaided eye. The granulations are approximately the same as those illustrated by Agassiz (1857:Pl. 7, Fig. 18) for T. carolina.