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

by John M. Legler

In juveniles, the yellow markings of the head and neck are larger and contrast more sharply with the dark ground color than in hatchlings. Markings above the eyes, if present, fuse to form two pale, semicircular stripes. In some older juveniles yellow marks on top of the head blend with the dark background to produce an amber color. The top of the neck darkens or develops blotches of darker color that produce a mottled effect. Spots and stripes on the side of the neck remain well defined. The skin on top of the head becomes smooth and shiny.

Adult females tend to retain the color and pattern of juveniles on the head and neck although slight general darkening occurs with age. Many adult females have the top of the head marked with bright yellow spots. In adult males, the top and sides of the head, anterior to the tympanum, are uniformly grayish green or bluish green; the mandibular and maxillary beaks are brighter, yellowish green. Markings on the head and neck of most adult males are obscure ([Pl. 25]) but the sides of the neck remain mottled in some individuals.

The antebrachium has large imbricated scales and is distinctly set off from the proximal part of the foreleg which is covered with granular skin. The antebrachial scales of hatchlings are pale yellow; each scale is bordered with darker color. General darkening of the antebrachium occurs at puberty. In adult females each scale on the anterior surface of the antebrachium is dark brown and has a contrasting yellow, amber, or pale orange center. The anterior antebrachial scales of adult males are dark brown to nearly black and have bright orange or red centers. Old males have thickened antebrachial scales.

The iris of hatchlings and juveniles is flecked with yellow and brown; the blending of these colors makes the eye appear yellow, golden, or light brown when viewed without magnification. Adult females retain the juvenal coloration of the eye; the iris of adult males is bright orange or red. The work of Evans (1952) on T. carolina suggests that eye color in box turtles is under hormonal control.

Wear

Presence or absence of areolae on laminae of the shell indicated degree and sequence of wear. The anterior edges of carapace and plastron, and the slightly elevated middorsal line ([Pl. 23]) wear smooth in some individuals before the first period of hibernation. Subsequent wear on the carapace proceeds posteriorly. For example, turtles that retained the areola of the third central lamina, retained also the areolae of the fourth and fifth centrals; when only one central areola remained, it was the fifth. Lateral laminae wear in the same general sequence. The areola of the fifth central lamina, because of its protected position, persists in adult turtles that are well past the age of regular growth. Areolae that are retained in some older turtles are shed along with the epidermal layers formed in the first year or two of life. Wear on the shell is probably correlated with the habits of the individual turtle; smoothly-worn specimens varied in size and age but were usually larger, older individuals. No smoothly worn individual was still growing.

Wear on the plastron is more evenly distributed than wear on the carapace; wear is greatest on the lowest points of the plastron (the gular laminae, the anterior portions of the anal laminae, and the lateral edge of the tranverse hinge).

The claws and the horny covering of the jaws are subject to greater wear than any other part of the epidermis; presumably they continue to grow throughout life. The occasional examples of hypertrophied beaks and claws that were observed, chiefly in juveniles, were thought to result from a continuous diet of soft food or prolonged activity on a soft substrate. Ditmars (1934:44, Fig. 41) illustrated a specimen of T. carolina, with hypertrophied maxillary beak and abnormally elongate claws, that had been kept in a house for 27 years.

The conformation of the maxillary beak in all species of Terrapene is influenced to a large extent by wear and is of limited value as a taxonomic character. The beak of T. ornata is slightly notched in most individuals at the time of hatching and remains so throughout life. The underlying premaxillary bone is always notched or bicuspidate. The sides of the beak are more heavily developed than the relatively thin central part. Normal wear on the beak maintains the notch (or deepens it) in the form of an inverted U or V, much in the manner of the bicrenate cutting edge on the grooved incisors of certain rodents. In a series of 34 specimens of T. ornata from Kansas, selected at random from the K. U. collections, 92 per cent had beaks that were "notched" to varying degrees, four per cent had hooked (unnotched) beaks, and four per cent had beaks that were flat at the tip (neither hooked nor notched).