Fig. 21. Plantar views of right hind foot (male at left, female at right) of T. o. ornata (× 1), showing sexual dimorphism in the shape and position of the first toe. The widened, thickened, and inturned terminal phalanx on the first toe of the male is used to grasp the female before and during coitus.
SEXUAL DIMORPHISM
Differences between adult males and females of T. ornata have been mentioned in several places in the preceding discussion of growth and development. Several sexual characteristics—greater preanal length, thickened base of the tail, slightly concave plastron, and smaller bulk—are found also in males of many other kinds of emyid turtles. From females, males of T. ornata are most easily distinguished by the bright colors of their eyes, heads, and antebrachial scales. An additional, distinctive characteristic of males is the highly modified hind foot. The first toe is greatly thickened and widened; when the foot is extended, the first toe is held in a horizontal plane nearly at right angles to the medial edge of the plantar surface ([Fig. 21]). The hind foot of females is unmodified in this respect. Males tend to have heavier, more muscular hind legs than females.
The bright colors of males are maintained throughout the year and do not become more intense in the breeding season. Males of T. o. luteola become melanistic in old age whereas males of the subspecies ornata do not. In old males of luteola the skin becomes dark gray, bluish, or nearly black and much of the bright orange or red of the antebrachial scales and the green of the head is obliterated; the iris may also darken but in most specimens it retains some red. Females of luteola tend also to darken somewhat in old age but not so much as males; females of ornata do not. Table 4 summarizes the more important secondary sexual characters of T. ornata.
Table 4.—A Summary of Sexual Dimorphism in Terrapene ornata | ||
| Character | Males | Females |
| Head | Snout truncate in lateral profile, top of head and front of maxilliary beak forming an angle of nearly 90°; head yellowish green to bluish green; markings on head and neck reduced; head never spotted dorsally ([Pl. 19, Figs. 7 and 8]). | Snout relatively round in lateral profile; front of maxillary beak not forming right angle with top of head; head dark brown, distinct pale markings on head and neck; head commonly spotted dorsally ([Pl. 25, Figs. 5 and 6]). |
| Iris | Red | Yellowish brown |
| Hind legs | Heavy and muscular; first toe turned in, thickened, and widened ([Fig. 21]). | Not especially heavy or muscular; first toe, if turned in, never thickened or widened ([Fig. 21]). |
| Forelegs | Centers of antebrachial scales bright orange or red. | Centers of antebrachial scales yellow, pale orange, or brown. |
| Carapace | Relatively lower, length contained in height (48 specimens) .58 times (± .005σm, range, .50 to .69). | Relatively higher, length contained in height (94 specimens) .50 times (± .005σm, range .44 to .60). |
| Plastron (hind lobe) | Ordinarily slightly concave. | Flat or convex, never concave. |
TEMPERATURE RELATIONSHIPS
Tolerances to environmental temperatures, and reactions to thermal stimuli influence the behavior of ectothermal animals to a large extent. Terrapene ornata, like other terrestrial reptiles inhabitating open grassland, is especially subject to the vicissitudes of environmental temperature. Other species of turtles living in the same area are more nearly aquatic and therefore live in a microhabitat that is more stable as regards temperature.
Approximately 500 temperature readings in the field and many others in the laboratory were obtained from enough individuals to permit interpretation of reactions involved in basking, in seeking cover, and in emerging from temporary periods of quiescence at various times of the day.
Box turtles commonly used open places such as cow paths, ravines, and wallows, for basking as well as for feeding and as routes of travel. Burrows, dens beneath rocks, and forms, were used as shelter from high and low temperatures as well as from predators. Determining whether a turtle was truly active (moving about freely, feeding, or copulating), was basking, or was seeking shelter was difficult because the turtle sometimes reacted to the observer; for instance, basking turtles, whose body temperatures were still suboptimum, might take cover when surprised, and truly active turtles might remain motionless and appear to be basking. By scanning open areas from a distance with binoculars, an observer frequently could determine what turtles were doing without disturbing them. In the final analysis of data, temperature records accompanied by data insufficient to determine correctly the state of activity of the turtle, were discarded, as were temperature records of injured turtles and turtles in livetraps.