May/June 2007For Wildlife Watchers: Gulf coast spiny softshell turtle by Rob Simbeck, photography by Steve Bennett
On the face of it, "softshell turtle" has an oxymoronic ring, like featherquill porcupine or rubbertooth shark. On at least three separate occasions, though, turtle species have traded in the bony plates that covered them for sleeker, leathery skin. It has happened for the leatherback and pig-nosed turtles—the only members of their respective families—and for softshell turtles, found in Asia, Africa and North America, including two species in South Carolina.
The advantages of such a trade-off? While it's seldom easy to pry secrets from nature, there are plenty of educated guesses when it comes to softshell turtles. The Gulf Coast spiny softshell, for instance, is aerodynamically an Indy car compared with some of its clunkier Jeep cousins, a feature that serves it well under water.
"Because they're flat," says S.C. Department of Natural Resources herpetologist Steve Bennett about the Gulf Coast spiny's sleek design, "they can hide under just a few inches of sand or mud, which is where they spend a lot of their time. They're hidden, camouflaged from predators, and they're in an ambush position when it comes to the species they feed on."
Under mud or sand, just its eyes and nostrils protruding, the Gulf Coast spiny softshell snatches small fish, amphibians or crustaceans as they go by, using lightning-quick moves of its long, retractable neck. It will also stretch that neck periodically to reach the surface and take a breath if it's in shallow enough water.
Gulf Coast spiny softshell turtle - Apalone spinifera aspera
Appearance: Like an olive-to-grey pancake with black spots. Has short, spiky spines on the front of its leathery carapace and stripes on the sides of its head. Females up to 18 inches. Males 10 inches or less.
Range and Habitat: Fresh water, particularly larger streams, rivers and managed wetlands. From northern North Carolina to northern Florida and to eastern Louisiana.
Reproduction: Breeds in April or May. Female lays 6 to 24 1-inch eggs, which hatch in late summer or fall.
Viewing Tips: These are daytime creatures, and warm weather and stealth are both essential conditions for viewing.
The other species native to South Carolina is the Florida softshell, which inhabits blackwater streams and ponds in the southern part of the state. The Gulf Coast spiny, primarily a river turtle, is found in the state's fast-flowing piedmont rivers and in streams and some ponds and lakes statewide. Large impoundments, like Lake Murray, and the Saluda River above Columbia have abundant populations.
The Gulf Coast spiny softshell looks like a spotted buckwheat pancake with legs. It's got a broad head with powerful jaws that can inflict a nasty bite on prey or bothersome humans—this is a fairly aggressive species—and an elongated, pig-like snout great for poking around, between and under rocks and crevices for aquatic insects and nymphs, and even some vegetable matter. Their feet have three claws and are webbed for good swimming, although these turtles move quickly on land as well. The shell has a sandpapery feel, and the species takes its name from spiked projections at the front of its top shell, or carapace. The underside is a naked white, and the bones are often visible through the translucent skin and small soft undershell, or plastron, which does not cover the rear legs or tail. Softshell turtles can pull their heads completely into their shells, where they are hidden by the leading edges of the carapace and plastron, which fold in.
This is a species that can "breathe" through its skin, trading oxygen and carbon dioxide across highly vascularized tissues, particularly at its throat and cloaca. That helps, of course, in reducing the need to surface as often for air, but that kind of porousness also makes softshells susceptible to the harmful effects of pollution.
Females are much bigger than males, reaching well over a foot in diameter, and sexual maturity comes late - eight or ten years for the females. The male's courtship, which takes place in April or May, involves waving his feet, extending his neck and touching the female's head; they mate in the water. She will dig a hole in a sunny gravel bank or sandbar with her hind feet to lay from six to twenty-four eggs, each an inch in diameter, often in June or July. The eggs gestate for eighty days or so, hatching in late summer or early fall. She will generally produce two clutches a year.
In cold weather, softshells slow down quite a bit, spending long periods buried in sand or mud. Still, says Bennett, "They're not as inactive as people think. You can go out any time of year and you might see turtles in a pond or stream. When the day warms up, they'll swim around a little bit, and when it's really cold they slow down. Their metabolic rate slows in winter, reducing their need for food and oxygen, but it's not like they go into true hibernation."
Eggs and young are prey to raccoons, fish, herons, snakes, foxes, skunks and other turtles. Primarily, though, softshell turtles have humans to worry about. Pollution is a concern, as is the greatly expanding Chinese market for turtles, given that country's newfound prosperity and its tradition of using turtles for food and medicine. Exports of turtles from this country to those markets have increased dramatically in the past two decades, and the population collapse of many species in Asia indicates how quickly turtles could be in trouble in South Carolina, especially given the long road to reproductive maturity.
In the meantime, Gulf Coast spiny softshells can still be spotted in many of the state's rivers and managed wetlands. They are most active during the day, and will sometimes sun themselves on the bank close to the water, although stealth is a must for wildlife watchers. These turtles are easily spooked and will return quickly to the water - and that quickness, of course, is one evolutionary advantage of having given up that hard shell long ago.