Softshell Turtles: Trionychidae
SOFTSHELL TURTLES: TrionychidaeSPINY SOFTSHELL (Apalone spinifera): SPECIES ACCOUNT
From above, softshell turtles look almost like rubber dinner plates swimming through the water. Although the turtles actually have a bony upper shell, it is completely covered by leathery skin, which usually reaches out past the edge of the bone and overlaps the tail and feet. The upper shell, or carapace (KARE-a-pays), is flat and often round. The turtles also have a tube-like snout and a long neck that they can pull in or extend out. Their webbed front feet each have three claws. A few species have flap-like hinges on the lower shell, or plastron (PLAS-trun), below the hind legs. Softshell turtles can be big or small, depending on the species. The smallest has a carapace that only measures up to 5 inches (12 centimeters) long, while the largest has a carapace ten times that length and sometimes more. In addition, most of them have a one-color carapace, but a few have stripes or spots. Sometimes, young turtles are more colorful. Usually, the males have longer tails than the females do. In some species, the males are smaller than the females, and/or more colorful.
Members of this family live in North America, Africa, and Asia.
These water-loving turtles live in all types of year-round fresh water, occasionally in ponds that dry up for part of the year. A few can swim into somewhat salty water for a brief time, but only one species, the Asian giant softshell, actually lives in the saltier waters of the coast. Overall, members of this family live east of the Rocky Mountains in North America and in mainly warmer climates in northern Africa, southern Asia, and the Indo-Australian archipelago, which is near Australia. They have also been introduced elsewhere, including Hawaii.
Most of these turtles are almost completely meat-eaters, and they eat anything they happen to come across, whether it is alive or dead. Once in a while, they will eat plants. A few species hunt by ambush, which means that the softshell turtle waits in hiding underwater — usually buried just under the bottom — for a fish or other water-living animal to swim by and then juts out its long neck and quickly grabs it with its mouth.
BEHAVIOR AND REPRODUCTION
For the most part, these turtles remain hidden for much of the day. They fall to the bottom of the lake, pond, or other watering hole where they live and wiggle their bodies back and forth until they are buried. When they move about in the water, they are excellent swimmers. Many species sunbathe, or bask, to warm their bodies. Some spend several hours a day basking on logs that stick up out of the water or on the shoreline, but they typically dash back into the water at even the slightest disturbance. Some prefer to sunbathe by simply floating in the top layer of water. They can breathe through the nose, but they can also get oxygen directly from the water, so they can stay below the surface for long periods of time. Those that live in colder areas enter a state of deep sleep, or hibernation (high-bur-NAY-shun), in the winter. During this period, which may last several months, they bury themselves in the sand or mud at the water bottom to wait for spring and warmer temperatures to come.
FLAPS FOR PROTECTION
Some species of softshell turtles have flaps near the hind legs that they can use to shield themselves from the glaring sun during dry spells. One species, called the Indian flapshell turtle, buries itself in the mud, pulls its legs inside its shell, covers up the hind legs with the flaps, and stays inside the shell in a state of deep sleep until the rains come. This period of deep sleep, which can last up to 160 days in this turtle, is called estivation (es-tih-VAY-shun). Estivation is similar to the inactive period known as hibernation (high-bur-NAY-shun), but hibernation occurs over the wintertime.
Softshell turtles usually mate each spring, although females can actually mate one year and have young from that single mating for several years. In some species, the male attracts the female by rubbing his chin on her carapace and bobbing his head at her. The female lays her round eggs in sandy, dry spots on shore. Depending on the species, a female may lay three to one hundred eggs at a time and have more than one clutch a year. The nests contain both male and female hatchlings, regardless of the nest temperature. In many other turtles, nest temperature controls the number of eggs that become male or female, but this is not known to occur in softshell turtles.
SOFTSHELL TURTLES AND PEOPLE
People hunt softshell turtles for food and to make traditional medicines. While many countries now have laws to protect at least some species, illegal hunting continues.
According to the World Conservation Union (IUCN), more than half of the family's 25 species are at risk. Five species are Critically Endangered, which means that they are facing an extremely high risk of extinction in the wild. In addition, five are Endangered and face a very high risk of extinction in the wild, and six are Vulnerable and at high risk of extinction in the wild. The U.S. Fish and Wildlife Service also lists four non-U.S. species as Endangered, or in danger of extinction throughout all or a significant portion of their range. Softshells are coping with overhunting, polluted waters that can weaken and/or kill the animals, and loss of their habitat.
Physical characteristics: Also known as a gooseneck turtle or leatherback turtle, the spiny softshell is a medium-sized turtle with a long neck and a rubbery upper shell, or carapace, with tiny spines at the front edge. Its flat carapace is mostly brownish green, but it has black spots and circles in both males and young turtles. The plastron is white or yellowish white. The turtles also have webbed feet, greenish legs usually mottled with black, and typically two yellow stripes on each side of the head. The carapace in females, which are about twice as large as the males, can reach up to 18.9 inches (48 centimeters) in length.
Geographic range: They live in Mexico, the United States, and Canada.
Habitat: Spiny softshells live in year-round, sandy- or muddy-bottomed bodies of fresh water, such as large lakes and ponds, as well as in shallow rivers and streams. They live in northeastern Mexico, the eastern half of the United States plus a few spots in western states, and into southeastern Canada.
Diet: Spiny softshells mostly eat meat in the form of just about anything they can find, including crayfish, fishes, and insects that live in the water. They will also eat acorns and leaves.
Behavior and reproduction: This turtle will bask on shore, but it quickly retreats at the slightest movement, so people rarely see them. Larger turtles especially also bask in the upper level of water. Usually, however, this turtle spends the majority of its days buried in the muddy or sandy bottom of its watery home. From this well-hidden spot, a turtle can keep an eye out for passing fishes or insects and dart out its long neck to grab the unsuspecting animal with its jaws for a quick meal. Because it can get oxygen directly from the water, the spiny softshell can stay underwater for long periods without drowning. Those that live in colder areas hibernate from fall to spring by burying themselves in the mud or sand beneath the water and remaining inactive.
Spiny softshells mate in the spring in deep waters. Scientists know little about their courtship or mating behaviors. In June and July, the female crawls on shore and then quickly digs a hole, drops the eggs inside, and covers it up. She provides no additional care for the eggs or the young turtles. She may lay two clutches a year. Each clutch contains four to thirty-two round eggs, each of which measures about 1.1 inches (2.8 centimeters) in diameter. They hatch in about fifty-five to eighty-five days. When the males reach four to five years old and the females reach eight to ten years old, they are ready to mate and become parents themselves. They live to be fifty years old or more.
Spiny softshells and people: People hunt this turtle for food, either to eat themselves or to ship overseas to meat markets in Asia. Some people also collect spiny softshells for the pet trade.
Conservation status: This species is not listed as endangered or threatened, although many of its nests are destroyed each year by raccoons and other animals that eat the eggs. ∎
FOR MORE INFORMATION
Behler, John L., and F. Wayne King. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Knopf, 1979.
Conant, Roger, and Joseph T. Collins. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Third Edition Expanded. Boston: Houghton Mifflin Co., 1998.
Harding, J. H., and J. A. Holman. Michigan Turtles and Lizards. East Lansing: Michigan State University Press, 1990.
Stebbins, Robert C. A Field Guide to Western Reptiles and Amphibians. Boston: Houghton Mifflin Co., 1985.