Turtles in Trouble: A Brief Natural History

For many, an encounter with a box turtle was their first childhood interaction with a wild creature.  There is something intrinsically wonderful about these little, rotund, bright-eyed reptiles.  Like rocks that can suddenly sprout eyes, limbs, and a short tail, box turtles seem to emerge from the woodwork as if from nowhere.  They delight us as they march through our backyards and gardens, in their single-minded pursuit of snails and earthworms.  Take a step too close, and they will quickly retreat into their high-domed shells with a little, nervous huff.  Inspection of the shell reveals a hard, well-crafted exterior, marked with elegant, yellow lines and blotches.  The surface is smooth or lightly ridged with tiny annuli like the rings of a tree.  Place the turtle back down, and within minutes two little eyes will be peeking out.

As a young boy, watching my Grandmother’s next-door neighbor’s turtle “Chip,” I never imagined that one day I would be part of a study focusing on box turtles (you can read about my experiences HERE).  These turtles brought nature to life for me as a youth, and now I was helping to increase our knowledge of how to protect them.  Box turtles, and the rest of their reptilian conspecifics, are in dire need of more people who understand them and recognize their peril.  Our turtles are in trouble. 

Northern Map Turtle

To fully understand our shelled companions, we must travel back 200 million years, to the late Triassic.  Here, an animal quite similar in appearance to modern day turtles, evolved.  This strange new creature made some amazing modifications to the vertebrate body plan.  Every piece of its anatomy had to be rearranged and adapted to fit inside a bony box.  The shoulder girdle moved inside the rib cage, which in turn fused together, encapsulating the internal organs.  The turtle’s spinal cord actually runs right down the center of the carapace (upper shell).

Midland Painted Turtle

Unique among vertebrates, the shell combined two types of bone: the shallow dermal bone and the strong, internal endochondral bone.  The surface became covered in a protective layer of large keratin scales (the same substance our fingernails and hair are made of) called scutes.  A turtle is its shell, and a shell is its turtle.  The commonly mis-held belief that a turtle can come out of its shell sounds perfectly ridiculous once you understand turtle anatomy.  

Why would turtles embark on such a strange evolutionary track?  This question is still a mystery that scientists struggle to understand.  Today, the shell’s main purpose is that of protection, but what evolutionary pressures drove its development, we can only guess.  One thing is clear, however, turtles have been extremely successful as their world has changed around them.  They survived the catastrophe that killed the dinosaurs, and persist in great abundance to this day.

Northern Map Turtles

Turtles are an iconic and easily recognized group.  They are split into the pleurodires, or side-necks, and the cryptodires, or hidden-necks (such as our familiar North American turtles).  The smallest species, the African padloper tortoises, grow to fewer than four inches in length.  Giants can be found on both land and sea.  The famous Galapagos tortoises can weigh over 500 lbs.  The largest of all living turtle species, the bizarre leatherback, can attain a length of almost six feet and a wingspan of nine feet.  This sea turtle has some decidedly unreptilian characteristics.  It has sacrificed its tough scales for leathery skin, and may even be able to regulate its internal body temperature like a mammal.  This allows it to swim into much colder and deeper waters than other sea turtles.

Snapping turtle laying eggs

Turtles are among the first of Ohio’s reptiles to emerge in spring, and among the last to disappear in fall.  Being ectotherms (cold-blooded), turtles need warm temperatures in order to become active, and can be seen out on logs basking during sunny days.  Most of the 12 turtle species found in Ohio are semi-aquatic, though a few, like the box turtle and the wood turtle, are more terrestrial and found in woodlands.

Snapping turtle egg

Early spring is the nesting season, and one of the few times when aquatic turtles venture any significant distance from their watery homes.  Females dig shallow ditches in loose soil, above the water line, in which to deposit their white, leathery eggs.  Turtle eggs are a favorite meal of raccoons; stream banks are often found littered with the shells of raided nests.  Many of Ohio’s turtle species (excluding the softshells) exhibit temperature dependent sex determination.  This means that the temperature at which the eggs develop dictates whether the eggs will hatch as males or females. Turtles do not care for their young.  Hatchlings emerge miniature versions of the adults, and are completely self reliant.  A hike near suitable pond, river, or forest habitat will almost certainly result in a glimpse of one of these timid reptiles.  

Despite living on land, box turtles are not tortoises.  Tortoises belong to the family Testudinidae, while box turtles belong to the family Emydidae—the pond turtles.  Taxonomy is based off of evolutionary relationships; members of a family are each others' closest relatives.  Box turtles are Terrapenes, a genus of pond turtle that has (with one exception) left the water for a primarily terrestrial life.  There are four species of Terrapenes: the eastern box turtle, ornate box turtle, spotted box turtle, and (the aquatic) coahuilan box turtle.  

The Eastern Box Turtle (Terrapene carolina carolina) is Ohio’s most terrestrial turtle species, found primarily in the southern half of the state.  They are short and stout reptiles, growing 5 to 6 inches in carapace (upper shell) length.  With the help of a hinged plastron (lower shell), these turtles can conceal their legs, head, and tail tightly within their shells—one of the few turtle species with this ability.  Box turtles are incredibly varied in appearance; no two look exactly alike.  Some are large, with prominent flaring around the shell, while others are small and rounded like a baseball.  Colors and patterns range from showy streaks of orange or even red, to unassuming spots of pale yellow.

It is a myth that the sexes can be told apart by the color of the eyes.  Females and males both have red eyes, and occasionally females and juveniles will have brownish eyes.  The best way to tell males from females is by the shell.  Females have a very high-domed carapace, and a flat plastron.  Males have a much lower carapace, and a concave plastron (helpful for mating).  Large, young-adult males will typically display pronounced fringes along the rear edge of the shell.  With age, the shells of both males and females weather and wear until they are smooth and rounded. 

Eastern box turtles are homebodies—living out their entire lives in an area of just 1 to 5 hectares (.0038 to .019 square miles).  They are primarily a woodland and edge species, though they can be found soaking in shallow pools in the heat of summer.  Turtles living in the same area often have overlapping home ranges.  Neither females nor males are territorial and they do not defend against interlopers.  It is not uncommon to find clusters of box turtles, with individuals only feet from one another, each apparently minding their own business.  The social dynamics of box turtles are not well understood.  It seems likely that turtles communicate with pheromones to a certain extent.  Pheromones certainly play a role in spring and summer when the turtles must find one another to mate.

Copulating pairs of box turtles have been found at all times of the active season, from early spring to late fall.  Mating can last several hours, during which the male’s rear legs are locked in the female's shell, holding him at an awkward 45 degree angle with the ground.  By storing sperm, females can produce viable clutches for years without the need to mate.  

Gravid (pregnant) females may travel a great distance from their home range to search for the perfect nesting location.  The female will dig a shallow hole in loose, sandy soil, and deposit 3 to 6 eggs.  Incubation lasts between 2 and 3 months, after which inch-long hatchlings emerge by midsummer.  The vast majority of box turtle hatchlings fall victim to predators like raccoons, skunks, and weasels.  It will take close to 10 years for a box turtle to reach sexual maturity.  Once a turtle has reached adult size, its chances of survival increase dramatically—some box turtles have been known to live well over a hundred years.                   

Turtles are known for being slow, and box turtles are no exception.  They have been nicknamed “sticky heels” for their plotting and awkward gait.  The slow and steady nature of turtles has helped them to survive for millennia, but in today’s age of the automobile, box turtles may have met their match.  Deforestation and land use changes have eliminated thousands of acres of turtle habitat.  Where they still survive, the criss-crossing of roads has created deadly barriers for these natural transients.  Turtles moving to lay eggs or to search out new home ranges inevitably find themselves crossing busy roadways.  It is unknown how many turtles perish on roads each day in the U.S., but the numbers likely reach the thousands.  Highways are particularly devastating for slow-moving herpetofauna like turtles, snakes, salamanders, and frogs.  In the span of just a few hours, I have moved more than a dozen box turtles from a single stretch of road in southern Ohio.  

Roads aren’t the only threat to box turtles.  Collecting for the pet trade and foreign markets has decimated turtle populations around the world.  Box turtles seem to hold a particular appeal as pets.  People who don't run over a turtle often decide to take the animal home with them.  Most of these impromptu turtle keepers know little of box turtle husbandry, and the captive turtles invariably waste away and succumb from improper care.  Despite wild turtles making poor pets, the commercial sale of box turtles continues in this country.  Thousands of turtles are exported to Europe and Asia and sold on the black market as pets and food.  This has put an unsustainable demand on these slow-to-reproduce reptiles. 

Deforestation, burning and mowing grasslands where turtles bask and nest, and a host of diseases have slowly but surely reduced North America’s healthy box turtle populations to disturbingly low numbers.  28 states have laws protecting box turtles, preventing the sale of wild-caught individuals.  In Ohio, box turtles are listed as a species of concern, though they are still considered common.  

When asked, “Why protect box turtles?” turtle-dog trainer John Rucker put it eloquently: “We don't really know what role they play.  But we do know that if we lose the turtles, we lose the checks and balances that keep nature in harmony.”  As both predators and prey, box turtles serve an important role transferring energy through the food web.  Without them, we don't know how the health and the diversity of the ecosystem would be affected.  Ignorance is not an excuse to lose our turtles.  They have existed far longer than we have, and deserve to continue their existence long into the future. 

They may not be fast or flashy, but box turtles speak to our humility and patience.  For as long as humans have studied them, turtles have been synonymous with longevity and time.  They are a creature to sit with in moments of reflection.  Next time you find a box turtle, stretch out in the leaf litter next to it.  Peer up through the undergrowth, and just watch the world go by.