The Staying Power of Snapping Turtles
Sure, snapping turtles are sometimes irascible and always prehistoric-looking. But these relics, which have been around for 90 million years, are the ultimate survivors.
Running across the Dartmouth College campus in Hanover, New Hampshire, around the western edge of Occum Pond, I spot a tiny snapping turtle alongside the road, motionless as if contemplating its future, which would have included trying to cross the road had I not intervened. The turtle is black, the size of a half-dollar, all legs and tail and neck (even at this tender age). Its eyes are mustard-colored, bright and inquisitive, its face hawklike, though it doesn't snap as I hold it between thumb and forefinger. On the turtle's cross-shaped lower shell, called the plastron, is a soft yellow oval with a tiny vertical slit, the remnant of the yolk sac and its omphalic connection to the hatchling, a mother turtle's only investment in her offspring besides her placement of the nest. The carapace, or upper shell, is crenellated, the margins spiky; three rows of sharp little points run down its middle like an archipelago. Unlike a box turtle, there's not much room for a hatchling snapper to withdraw into its shell, the chelonian equivalent of being born too big for your breeches, a lifelong morphological fact that may contribute to an adult snapper's irascible disposition on land.
When I release the snapper into Occum Pond, it sinks into the ooze and then swims away, a plume of silt trailing behind, an easy meal for an aquatic predator--bass, pickerel, bullfrog, or heron--and maybe one reason a female snapping turtle lays a clutch of 26 to 55 eggs (sometimes more than 100) each year beginning at age 11 or 12 in the Northeast and continuing for 20 years or more. (Snapping turtles in South Florida may breed more than once a year, partly because there is no need for hibernation in the steamy subtropics and maybe partly to compensate for heavy losses to the snap-trap jaws of hungry alligators.)
"Turtles are a kind of bird with the governor turned low," wrote Edward Hoag-land, a reference to their lethargy (and longevity). In my corner of the Northeast, snapping turtles hibernate five or six months a year, dreaming turtle dreams tucked beneath a blanket of anoxic mud in the weedy, eutrophic shallows of ponds, marshes, and lakeshores, their pilot lights barely flickering. The ability to endure exposure to low levels of dissolved oxygen permits snapping turtles to winter in sites that are off-limits to wood turtles, which need much higher levels of dissolved oxygen during dormancy. Consequently, snapping turtles are far more common and far more commonly encountered than wood turtles. They're most often seen in late spring, when females search for nest sites, and in early autumn, when hatchlings like the one I ferry to Occum Pond emerge from their earthen wombs to negotiate a gauntlet of terrestrial predators, including everything from chipmunks to crows to shrews, on their way to water.
The snapping turtle family, Chelydridae, evolved in North America and has haunted our wetlands almost unchanged for nearly 90 million years. Ancestors spread to Eurasia about 40 million years ago and then disappeared from that continent in the late Pliocene, about two million years ago. Chelydrids have been sequestered in the Western Hemisphere ever since, which makes them among our truest and oldest turtles. They were present when dinosaurs lived and died, and had been laying round, white, leathery eggs in sandy loam and glacial till for millions of years when the first Amerindians wandered over the Bering Land Bridge. Snapping turtles have witnessed the drift of continents, the birth of islands, the drowning of coastlines, the rise and fall of mountain ranges, the spread of prairies and deserts, the comings and goings of glaciers.
They range across southern Canada from Alberta to Nova Scotia, throughout the eastern two-thirds of America from the apron of the Rocky Mountains east to the tidewater Atlantic, and south to the Gulf Coast and the Mexican tributaries of the Rio Grande. Two sibling species dwell in the tropics--one ranging from the Atlantic lowlands of Vera Cruz, Mexico, to Honduras, and the other from Nicaragua south through Caribbean Central America to the Pacific coast of Colombia and Ecuador. Like their northern cousin, both species seek mud-bottomed, weed-choked wetlands, and are opportunistic feeders, dining on whatever is available: carrion, aquatic invertebrates, fish, amphibians, other turtles, small mammals, snakes, the occasional bird (ducklings usually), and all manner of aquatic plants, which may make up more than half their diet.
As is the case with rattlesnakes, the snapping turtle's reported nature is addled by exaggeration, and no characteristic is more hyperbolized than its bite. Googling "snapping turtle" yields results that highlight human misperceptions of this big, bigheaded chelonian, the beast with an iniquitous, but mostly undeserved, reputation. When I was growing up on Long Island, suburban legend claimed that a large, hatchet-faced snapping turtle--common in streams, sumps, and tidal marshes along the South Shore--could break a broom handle in one bite. Years later I tested the hypothesis, which proved false.
A few years ago the blog BirdForum, for example, ran a dialogue called "Are snapping turtles killing our birds?" Someone whose mother blamed the much-maligned turtle for a reduction of geese on a local lake inquired, "Do snapping turtles actively hunt down adult-sized Canadian geese?" One correspondent suggested that the fleshy lure on the tongue of the snapping turtle (actually the lure is on the tongue of the closely related but much larger alligator snapping turtle, of the Mississippi drainage) attracts geese. The curious goose then gets "its head chomped on my [sic] the turtle."