Eastern Box Turtles—Frozen Alive!

After my family moved to northern Idaho, I recalled fond memories of my childhood back East. When a high-school friend told me he was planning to visit the East coast, I asked him to bring back a living reminder of my past—a box turtle. He obliged and brought a beautiful male specimen, which I named “Waldo Pepper.”

I built an outdoor pen in which Waldo puttered about throughout the summer. When winter approached, he dug a shallow burrow to prepare for the cold. I piled autumn leaves over him and covered everything with a small tarp. It can get bitterly cold in Idaho, but that winter was unusually frigid. I remember it dipped down to 30°F below zero (-34°C).

When spring came, I must admit that I wasn’t hopeful to find Waldo alive. On the first warmish day I anxiously scraped away the leaves. I saw the top of his shell, barely below ground level. “He didn’t dig deep enough,” I worried. “He’s sure to be dead.” I touched his shell and to my delight it lurched as he moved within. He had made it through that wintery blast!

I knew box turtles “hibernated,” but I had no clue how he could survive being frozen alive. It didn’t matter to me. Waldo was alive and well!

Uncovering the Turtle’s Secret

If you’re native to the eastern half of the United States, you’re probably familiar with the eastern box turtle. During the summer you’ll see them lumbering across roads, or if you have a keen eye, you’ll spot them blending in among the jumble of yellow, red, and brown leaves on the forest floor.

Males may be looking for a mate while females are looking for a place to lay eggs, or they may simply be hunting for a nice snack of beetles, worms, slugs, berries, or mushrooms, or for a good place to dig in for the night.

However, when winter’s chill approaches, you probably won’t see them anymore, even if you look hard. They’re dug in for the winter, riding out the cold and storms within their icy burrows.

God equipped them with antifreeze!

Box turtles truly take “hibernation” to another level.1 What special provision enables these four-legged tanks to endure subzero weather in such woefully shallow burrows? The answer sounds almost like science fiction. God equipped them with antifreeze!

When a box turtle begins to experience chillier temperatures, its liver releases lots of glucose (a simple sugar) into the bloodstream. The sugar is then concentrated in various organs and acts as a sort of biological antifreeze. The places that are the most protected are the liver, heart, and blood serum. The brain and eyes are also filled with glucose.

Meanwhile, water is moved out of the cells and into body cavities, where it is allowed to freeze. The high glucose and low water levels prevent ice crystals from forming within cells. (Ice crystals would spell doom for cells because they puncture their membranes.)

So where does the ice form? Some researchers found ice packed around the brain, leg muscles, and in the body cavities around and between other organs. Even the lungs become icy chunks of tissue. When temperatures get really frigid, even the heart stops beating!

Another study found that up to 58% of the turtle’s body water could be frozen solid for at least 73 hours. It’s like a temporary “death” without decay. Once the turtle thaws out, it appears to be no worse for the wear. When spring arrives, the various organs gradually “come back to life.” This is kind of a “death and resurrection” every winter and spring.

The Main Danger Today

In eternity past—before God created the first turtles and humans—He knew that Adam would sin and bring a curse upon His world. Weather would fluctuate wildly, especially after the Flood, so box turtles and all other creatures would need to be prepared for the extremes.

Designed for Defense

Photo courtesy Gordon Wilson

Eastern box turtles are land turtles and can’t escape threats the way many river and pond turtles do. These water turtles can simply plop into the water. But since box turtles don’t usually have that option, God has equipped them with other protective measures.

BATTEN DOWN THE HATCHES. Even though they are well camouflaged, box turtles are not invisible. Predators do find them, and of course land turtles can’t sprint to safety. So God has equipped them with a suit of armor (the upper and lower shells). The lower shell, or plastron, is hinged so that the front and back can seal tight against the upper shell (left). Meanwhile, the turtle’s head, legs, and tail are tucked safely away.

Although we live in a fallen world where many animals face the ever-present threat of extinction, God has graciously equipped His creatures to be downright durable. In most cases, each kind of creature possesses enough “tricks up its sleeve” to endure the worst extremes various habitats might offer. Even when critters are relocated (like Waldo’s move to Idaho), they can often endure harsher conditions.

Despite their God-given toughness, many creatures face another serious threat. Though God told mankind to be a good steward of His creation, at times humans can become its worst enemy. Many times we unnecessarily damage habitats beyond what creatures can endure.

Box turtles, for example, are slow movers, slow to mature, and limited in the distances they typically travel. They do not reproduce until age seven or so, and even then they typically lay three to four eggs at a time.

So whenever humans cut down forests and build towns and roads, it is more difficult for a turtle to find food, a mate, and a safe place to nest. Road crossing is very risky business for a turtle, and countless turtles are killed each year trying to attempt it.

I did my PhD research on the reproduction of the eastern box turtle, and one interesting fact I discovered is that females often travel well outside their wooded “stomping grounds” to forest edges, fields, and yards to lay eggs.

Females loaded with eggs are more likely to attempt dangerous road crossings in their effort to find a suitable nest site. So it is generally unwise to release a pet box turtle anywhere except where it was caught (even woods containing other box turtles). Why? The turtle will often instinctively try to return home, crossing every road in its way. Unwittingly, we stack the deck against the turtle’s survival.

God cares about the welfare of animals. Do you remember why He had Noah fill the Ark with animals? “To keep their various kinds alive throughout the earth” (Genesis 7:3, NIV). The fact that He gave His creatures so many amazing designs for survival, such as antifreeze, reinforces how much He cares about them. If He cares so much for His creatures, shouldn’t we, as appointed stewards of His creation, do the same (Genesis 1:26)?

References

J. P. Costanzo and D. L. Claussen, “Natural Freeze Tolerance in the Terrestrial Turtle, Terrapene carolina,” Journal of Experimental Zoology 254:228–232.

J. P. Costanzo, R. E. Lee, Jr., and M. F. Wright, “Physiological Responses to Freezing in the Turtle Terrapene carolina,” Journal of Herpetology 27:117–120.

C. K. Dodd, North American Box Turtles: A Natural History (Norman, Oklahoma: University of Oklahoma Press, 2001).

K. B. Storey et al., “Freezing Survival and Metabolism of Box Turtles, Terrapene carolina,” Copeia 1993 (3): 628–634.