THREE TOED BOX TURTLE (Terrapene carolina triunguis), (AGASSIZ, 1857)
IDENTIFICATION: The carapace is highly domed and may range in color from tan or beige, to dark brown. Their shells may be marked with a variable assortment of spots, lines, a combination of the two, while some are completely void of any markings at all. The limbs may also be as variable in coloration as the carapace. Flesh coloration of dirty white, creamy yellow, tan, or brown may be present. The coloration of the scales present on the fore and hind limbs is often vividly contrasting enough to resemble the spilled paints on an artist's canvas. Scales of brick to vivid red, yellow, orange, and white easily disrupt the earth tone coloration of this turtle's other features. The face is often adorned in attractive colors. Variable patterns of white, red, purple, magenta, orange, and yellow are often found on the faces and heads of many individuals. However, facial coloration seems to bear the strongest contrast near the beak. On this area of the face many of the aforementioned colors can provide the appearance of a "mustache of color." The name "three-toed box turtle" is obviously due to the three toes found on their hind feet. However, some individuals have been found with four toes.
For reasons currently unknown, many three-toed box turtles have paired pits in their carapace. The pits measure 4-5 mm in diameter and actually go through the keratin scutes and into the bony dermal layer. There has been speculation that the pits were caused after the turtles had been picked up by canine predators. However, this is not likely to be the reason as there is often only one pit per side and they occur in approximately the same location on the shell among different specimens. To date, the explanation for shell pits remains uncertain. However, it is likely an artifact of bone growth.
NATURAL HISTORY AND ECOLOGY: These turtles occur in damp grasslands, within and at the edge of open deciduous and coniferous forest, and near permanent and temporary bodies of water. A study of microhabitat selection in the three-toed box turtle revealed that this species lives within a limited microhabitat range at all times during its annual activity (Reagan, 1974). The results indicated that the turtles selected humidity levels independent of prevailing conditions at the surface (Ernst, et al., 1994).
REPRODUCTION: Male three toed box turtles attain a larger size than the females and there may be a slight concavity to the posterior of the male's plastron. This combined with strongly curved hind claws helps the males achieve mating success. Aside from these two features, male three-toed box turtles tend to have a noticeably "redder" eye than the females. The tail normally allows a sure method to determine the sex. The male's tail is longer and thicker than that of the female. In males, the cloaca may also extend beyond the posterior marginal scutes. However, these features may vary from population to population. If in doubt an assessment of all characters thought to be sexually dimorphic should be made to help ensure a correct sex determination.
Mating begins in the spring after the turtles are revived from hibernation. Females have the ability to produce up to four clutches of eggs from a single mating by storing sperm cells in the lining of their oviducts. Long-term captive females in my care regularly lay their clutches of 2-7 eggs in late June to early July. Incubation under artificial conditions takes about 70-80 days. Nesting is generally the only time when females will be found active after dark.
Hatchlings are carnivorous and consume a wide variety of prey including, worms, insects, pill bugs, and other invertebrates. As the three-toed box turtle matures, its diet shifts to include more vegetative matter. Adults are typically omnivores of broad culinary desires. Food items known to be consumed by adults include: carrion, slugs, snails, beetles, worms, frogs, snapping turtle eggs, baby mice, grasses, fungi, bones, caterpillars, centipedes, and crayfish.
Computer tomography (CT) scan of baby 3 toed box turtle that died just one day before hatching. Notice the incomplete appearance of the skeleton and shell