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Box Turtle Basics


What is a Turtle?

All turtles, tortoises, and terrapins are reptiles and share the characteristics of reptiles: they all have dry, glandless skin covered with scales; most lay eggs; all are amniotes (animals whose embryos are surrounded by an amniotic membrane); and they are all ectothermic (control their body temperature through external means). Turtles are sometimes called chelonians because they are in the taxonomic order called Chelonia (from the Greek word for "tortoise"). All turtles have some type of shell and this makes them unique from other reptiles.

So why the different names? The common names, turtle, tortoise, and terrapin, usually refer to differences in where the animal lives and how it uses the habitat. But the names are also used differently in different parts of the world. For instance, in Australia, only sea turtles are called turtles; everything else is called a tortoise. In Britain, a "turtle" would mean a saltwater species and a "terrapin" would be a freshwater species. For most Americans, the term "turtle" describes chelonians that are aquatic or semi-aquatic while the term "tortoise" is used for those in drier land habitats. Terrapin can apply to animals living in some freshwater or brackish, swampy areas and comes from an Indian word meaning "little turtle". Most box turtles spend a large part of their time on land but do enter shallow water from time to time.

Eleven different kinds of box turtles occur in North America: six in Mexico and five in the U.S. Arkansas is home to two different box turtles, theThree-toed box turtle (Terrapene carolina triunguis) and Ornate box turtle (Terrapene ornata ornata). The Three-toed box turtle is found nearly statewide. Chances are, if you see a box turtle in Arkansas it is most likely a Three-toed box turtle. The ornate box turtle is restricted to parts of the state that once contained tallgrass prairies.

Shell Structure

Box turtles share a physical feature in common with all other turtles: they have a shell that protects their soft organs. Box turtles can also retract their head and limbs into their shells and close the shell for added protection. In order to make room inside the shell, they sometimes have to exhale air out of their lungs, which makes a hissing sound.

The outer layer of the shell is covered by horny scales called scutes that are part of the outer skin or epidermis. Scutes are made up of a fibrous protein called keratin that also makes up the scales of other reptiles. These scutes overlap the seams between the shell bones and add strength to the shell. Turtles can feel pressure and pain through their shells, just as you can feel pressure through your fingernails.

The shape of the shell is also important. Adult box turtles have a large dome-shaped shell that is difficult for predators to crush between their jaws. Hatchling box turtles do not have a hinged shell but develop one after a year or two.

Three-toed and Ornate

The Three-toed box turtle, as its name implies, generally has three toes on each hind foot. However, specimens with four toes have been observed, so this is not a failsafe method for identifying a Three-toed box turtle. The upper shell (carapace) of Three-toed box turtles can vary in color depending on the age of the turtle. The carapaces of immature Three-toed box turtles are typically olive brown with faint yellow to orange markings. As the turtle ages, these markings fade and the carapace becomes a uniform olive-brown. The lower part of the shell (plastron) is generally unmarked.



Ornate box turtles are more colorful and more "ornate" than the Three-toed. Their carapace ranges in color from dark brown to nearly black and is marked by several radiating yellow lines. The plastron of the ornate is dark in coloration and marked by radiating yellow lines in contrast to the drabber plastron of the Three-toed. Ornate box turtles typically have four toes on each hind foot, though individuals with three toes have been noted. Plastron coloration is the recommended character to use when differentiating between the two species.

The head, neck, and forelegs of both species are often marked by mottling or blotches of yellow, orange, and red. The sex of adults of both species can be differentiated based on eye color; males have red eyes whereas female have brown. Adult males also have longer tails and concave plastrons. The tails of females are shorter and their plastrons are flat.


Habitat

Across its range, the ornate box turtle is associated with dry, open habitat types such as remnant tallgrass prairies in the Arkansas River Valley, Grand Prairie, and Ozark Mountains. The three-toed box turtle is associated with forests and woodlands as well as marshes and grasslands.

Diet

Box turtles are omnivorous, consuming a variety of animal and plant material. The habitat of each species plays a role in its diet. The ornate box turtle may eat more animal matter, based on the food value of dry prairie plants. Three-toed box turtles, especially as they age, tend to eat more plants and have access to a greater variety in the forests and woodlands. Box turtles do prey on other animals, including invertebrates such as beetles, grasshoppers, earthworms, crayfish, to snails. Box turtles have also been known to catch frogs, salamanders, and hatchling birds. Both species will also readily consume carrion (dead animal flesh). Box turtles eat a wide range of plants including blackberries, mulberries, prickly pear, persimmons, mushrooms, and dandelions. Box turtles use their jaws to cut and chew food. Instead of teeth, the upper and lower jaws are covered by horny ridges. Turtles use their tongues to swallow food, but they cannot, like some other reptiles, stick out their tongues to catch food.

Age

The lifespan of an ornate box turtles can be at least 32 years and as long as 42 years. The lifespan of three-toed box turtles have been recorded as between 40 to 70 years. Turtle age can be estimated in younger turtles by counting the growth rings on the carapace. This method of age determination is only useful until about 10-15 years of age. As box turtles mature, growth rings wear down and become indistinguishable.



Home Range

A box turtle's home range is the area where it conducts all activities of its life, from overwintering, feeding, to mating. The size of a box turtle's home range depends on a number of factors, including the turtle's age and the habitat quality. Researchers have documented the home ranges of three-toed and ornate box turtles to be as small as three acres or as large as 100 acres. Box turtles appear to have the ability to remember landmarks and the location of food and shelter within their home ranges. Their strong familiarity with the characteristics of their home range contributes to their strong homing instinct. Box turtles removed from their home range and relocated some distance away, will generally not stay in a new, unfamiliar location. Instead, these displaced turtles will travel long distances in order to relocate their original home.

Reproduction

Box turtles become sexually mature around 13 years of age. Mating takes place anytime from April to October. Female box turtles store sperm over the winter and eggs are fertilized the following summer. Nesting typically occurs in spring or early summer. Females dig nest cavities in the ground into which they deposit 2-6 eggs. The nest cavity is filled and then concealed with plant debris. The length of time before the eggs hatch varies based upon temperature (2 to 4 months). The sex of hatchlings appears to be determined by temperature; with more males produced at low temperatures, and more females produced at warmer temperatures. Hatchlings emerge in the fall but will often continue to use their nest cavity as an overwintering site.

Overwintering

As air temperature cools in the fall, box turtles curtail activity and head for overwintering sites. Box turtles will burrow under leaf litter and into soil in preparation for hibernation. Most box turtles spend the winter with the top of their shells just a few inches below the surface. Box turtles will also utilize old mammal burrows and decaying logs as hibernation sites. They have unique physical adaptations that shut down their extremities as the temperature drops, eventually keeping blood in only their brain and heart. During long cold periods, their heart may even stop beating for a time. They are the largest animal in North America that can withstand freezing and scientists do not fully understand the factors that allow them to "restart" each spring. this is a test.


Next article: Threats to Box Turtles
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