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Smooth Softshelled Turtle

Apalone mutica

What do they look like?

Smooth softshell turtles are medium or large turtles that live in freshwater. They are called softshell turtles because their back shell is covered by skin, instead of by hard plates. The shell is shaped like an oval, and doesn't have spines on the front edge. Females have a tan or brown back shell that is 16.5 to 35.6 cm long. Males have a brown or gray back shell that is 11.5 to 26.6 cm long, and thick tails. Their heads, legs, and tail are about the same color, and they have a cream or orange line with a black border going from the back of their eye to their neck. They both have dark spots, streaks, or blotches on their shells. Very young smooth softshell turtles have a brown or olive back shell with lots of markings. Smooth softshell turtles look a lot like spiny softshell turtles. Spiny softshell turtles have spines on the front of their shell, so they feel like sandpaper to the touch. (Ernst and Lovich, 2009; Minnesota Department of Natural Resources, 2011; Oldfield and Moriarty, 1994)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range length
    males 11.5 cm; females 16.5 to males 26.6 cm; females 35.6 cm
    to in

Where do they live?

Smooth softshell turtles live in the central and south-central United States. They are found from Pennsylvania to New Mexico and south to the Florida panhandle. Actually, they may not live in Pennsylvania anymore. Smooth softshell turtles are native to North America. They probably lived here since the Cretaceous Period, which was 65.5 to 145.5 million years ago. They have also been introduced to France. There are two subspecies of smooth softshell turtles. Midland smooth softshells are found in the central United States, and Gulf coast smooth softshells live in the area from Louisiana to the panhandle of Florida. (Ernst and Lovich, 2009; Ernst, et al., 1994; Hulse, et al., 2001; Oldfield and Moriarty, 1994; Quammen, 1992)

What kind of habitat do they need?

Smooth softshell turtles live in and around large rivers like the Ohio, Missouri, and Mississippi rivers, and also in the smaller rivers that run into them. They like larger rivers and streams with medium to fast currents. The most common place to find them is in southern Illinois. Though they like rivers best, smooth softshell turtles are also found in lakes, bogs, ponds, and drainage ditches. They like places with sandy or mucky bottoms that don't have a lot of plants or hard bottoms. In the Kansas River, they are found in shallow waters. Gulf coast smooth softshells live mostly in rivers and streams, but midland smooth softshells also live in lakes, bogs, ditches that collect water, and ponds. (Barko and Briggler, 2006; Bodie, et al., 2000; Ernst and Barbour, 1972; Ernst and Barbour, 1989; Ernst and Lovich, 2009; Oldfield and Moriarty, 1994; Plummer, 1977)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • Range elevation
    1300 (high) m
    4265.09 (high) ft

How do they grow?

Smooth softshell turtles start developing inside an egg. Cells divide, tissues form, and then organs. Whether the baby is a boy or girl doesn't depend on temperature like it does in some turtles. About the same number of males and females are born. At birth, the back shell is round, but it grows into an oval shape. They usually grow between May and September, especially in June and August. Most turtles keep growing throughout their whole lives, but scientists aren't sure if smooth softshell turtles do this or not. (Browne and Hecnar, 2007; Ernst and Lovich, 2009; Ewert, 1985; Nagle, et al., 2003)

How do they reproduce?

Smooth softshell turtles breed from April to June, and possibly into September. Males go looking for females, and approach other turtles to see if they can mate with them. (Ernst and Barbour, 1972; Ernst and Lovich, 2009; Oldfield and Moriarty, 1994)

Smooth softshell turtles nest between late May and July. Females use their back feet to dig a nest 15 to 30 cm deep on a sand bar. Nests are usually within 18 m of water, and hardly ever more than 30 m away. They can be close to other nests, and even have chambers connecting them. They are usually 0.5 to 6.1 m above the water. If something happens to the nest, females give up and leave. They usually lay 15 to 25 eggs in the early morning, and cover them with their back feet. They lay more eggs earlier in the season and less eggs later in the season. Then, females dig out a tunnel up to 4 m long and rest across from the nest. About 75% of the eggs survive. (Ernst and Lovich, 2009; Oldfield and Moriarty, 1994; Plummer, 1976; Vogt, 1981)

Eggs take about 8 to 12 weeks to hatch, so they usually hatch in August or September. Baby turtles break through the eggs mostly using their front claws. They have the same special tooth for breaking out of eggs like many reptiles, but don't use it as much. They usually come out of the nest around sunset, and are completely independent right away. When they hatch, they are 4 cm long on their back shell. They weigh 3.0 to 7.5 g, or 5.4 g on average. Males are able to have their own young when they are 4 years old, and females when they are 9 years old. ("Smooth softshell (Apalone mutica)", 2009; Doody, 1996; Ernst and Barbour, 1972; Ernst and Lovich, 2009; Oldfield and Moriarty, 1994; Plummer and Shirer, 1975; Plummer, 1977)

  • How often does reproduction occur?
    Female smooth softshell turtles have one clutch per year.
  • Breeding season
    In Minnesota, breeding occurs in May and June, and nesting occurs in June and July.
  • Range number of offspring
    1 to 33
  • Average number of offspring
    15 to 25
  • Range gestation period
    8 to 12 weeks
  • Range age at sexual or reproductive maturity (female)
    7 (low) years
  • Average age at sexual or reproductive maturity (female)
    9 years
  • Average age at sexual or reproductive maturity (male)
    4 years

Smooth softshell turtle females produce fats to give energy to growing baby turtle embryos. Babies use the fats they are born with as food until they are old enough to feed themselves. This helps them survive even if food is scarce. After the babies hatch, smooth softshell turtles don't invest any more time or energy into the young. (Ernst and Lovich, 2009; Nagle, et al., 2003)

  • Parental Investment
  • pre-hatching/birth
    • provisioning
      • female

How long do they live?

It's very hard to tell how old smooth softshell turtles are in the field. In captivity, they have lived more than 11 years, but scientists think they can live up to 20 years. This is because their relatives Florida softshell turtles and spiny softshell turtles can live up to 25 years in captivity. (Ernst and Lovich, 2009; Snider and Bowler, 1992)

  • Average lifespan
    Status: captivity
    11 years

How do they behave?

Smooth softshell turtles spend more time in the water than any other North American softshell turtles. They can stay underwater for long periods of time, partly because they have long necks and noses. They bury themselves in the sandy bottom with their nose sticking up just above the surface. They stir up the sand around them so that it covers their bodies and only their head shows. They also hibernate like this in the winter. In Kansas, they come out of hibernation in March or April. Farther north like in Minnesota, they keep hibernating until May. When they come out from hibernation, they lay out in the sun on sand bars, in shallow water, or on logs or rocks. They move away quickly if they sense danger from predators. They are quick and agile, which helps them escape from predators and also catch prey. Smooth softshell turtles usually spend time alone. (Degenhardt, et al., 1996; Ernst and Lovich, 2009; Jackson, et al., 1976; Lindeman, 2000; Oldfield and Moriarty, 1994; Plummer, 1977; Vogt, 1981)

Home Range

Due to the high frequency of time spent in water, most recorded movements of smooth softshell turtles are aquatic-based. During the breeding season, females move around land bars during their search for suitable nesting habitat. A 1975 study in Kansas found that radio-equipped males had a mean linear home range of 474 m. The mean linear home range of subadult females was 750 m and of adult females was 1,228 m. Adult females had the greatest activity within their home range. (Ernst and Lovich, 2009; Plummer and Shirer, 1975)

Smooth softshell turtle females move around quite a bit when searching for nesting habitat. As adults, they usually have an area about 1,2228 m long where they generally feed and live. The size of this area is 474 m for males and 750 m for young females. (Ernst and Lovich, 2009; Jackson, et al., 1976; Oldfield and Moriarty, 1994; Plummer and Shirer, 1975)

How do they communicate with each other?

Smooth softshell turtles use mostly body language and touch to communicate. Males use their sense of touch to sense females they might mate with. Scientists don't know much about how they communicate. However, their relatives spiny softshell turtles use sight, touch, chemical signals, and vibrations to understand their environment. (Bartholomew, 2002; Ernst and Lovich, 2009)

What do they eat?

Smooth softshell turtles eat many kinds of animals, especially insects. They also eat fish, amphibians, arthropods, spiders, snails, mollusks, isopods, millipedes, and worms. The insects they eat are beetles, flies, blow-flies, nonbiting midges, circular-seamed flies, Empididae flies, Muscidae flies, shadflies, crane flies, bugs, sawflies, wasps, bees and ants, aphids, scale insects, cicadas, and leafhoppers, termites, moths and butterfiles, ichneumon wasps, dragonflies and damselflies, net-winged insects, grasshoppers, crickets, weta, and locusts, stoneflies, and caddisflies. The kinds of fish they eat are white suckers, steelcolor shiners, spotfin shiners, bluegill, white bass, northern hogsuckers, yellow perch, and brook trout. Though smooth softshell turtles east mostly other animals, they also eat plants like algae, potatoes, seeds, stems, mulberry, fruits, and hard nuts. (Ernst and Lovich, 2009; Oldfield and Moriarty, 1994)

Smooth softshell turtles hunt both on land and in water. They are called ambush predators, which means that they hide at the bottom of the water covered in sand and grab prey with their long necks. They also gulp in small nearby prey, or find food in sand and plants with their nose. Females get food from deeper water than males. (Ernst and Lovich, 2009; Oldfield and Moriarty, 1994; Plummer and Farrar, 1981)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • fish
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • mollusks
  • terrestrial worms
  • aquatic crustaceans
  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • seeds, grains, and nuts
  • fruit
  • algae

What eats them and how do they avoid being eaten?

Smooth softshell turtles don't have many natural predators because they are quick and move around easily. The main predators of adults are humans and alligators. Young smooth softshell turtles are eaten by fish, other turtles like common snapping turtles, alligator snapping turtles, and maybe their relatives, water snakes, shoreline birds, bald eagles, and other mammals. Their nests are preyed on by raccoons, skunks, crows, fire ants, fly larvae, dogs, red foxes, eastern moles, and other small mammals. Smooth softshell turtles avoid predators by quickly moving away if they sense danger. They are good at diving and hide in the mud. If they are caught by a predator, they pull themselves into their shell. (Doody, 1996; Ernst and Lovich, 2009; Fitch and Plummer, 1975; Oldfield and Moriarty, 1994; Vogt, 1981)

What roles do they have in the ecosystem?

Smooth softshell turtles eat other animals from the water and are also hunted by many animals. Their eggs get fly larvae in them as parasites. (Ernst and Lovich, 2009)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

Smooth softshell turtles might sometimes eat fish that humans trade, or bite humans if they are picked up. (Ernst and Barbour, 1972)

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings

How do they interact with us?

In some places, humans eat smooth softshell turtles as well as their eggs. They are also sometimes traded as pets. (Ernst and Lovich, 2009)

Are they endangered?

Smooth softshell turtles not considered endangered, and are common where they live. However, there's not a ton of information about how many there are, and they are listed as "special concern" in Minnesota. They are more at risk than other animals because they grow slowly. They also are vulnerable to water pollution, because they get oxygen from the water. They are also threatened by damage to their habitat, hunting, river dams, and humans messing up their nesting spots. They are also caught by accident in the fishing business. They would be better off with more protection of the waters and land where they live. (Ernst and Lovich, 2009; Ernst, et al., 1994; Minnesota Department of Natural Resources, 2011; Moll and Moll, 2000; Pappas, et al., 2001; Trauth, et al., 2004; van Dijk, 2010)

Some more information...

The scientific name of smooth softshell turtles used to be Trionyx muticus. (Ernst and Lovich, 2009)

Contributors

Jeana Albers (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Gail McCormick (editor), Animal Diversity Web Staff, Catherine Kent (editor), Special Projects.

References

2009. "Smooth softshell (Apalone mutica)" (On-line). Wisconsin Department of Natural Resources. Accessed April 15, 2011 at http://dnr.wi.gov/org/land/er/biodiversity/index.asp?mode=info&Grp=49&SpecCode=ARAAG01020.

Barko, V., J. Briggler. 2006. Midland smooth softshell (Apalone mutica) and spiny softshell (Apalone spinifera) turtles in the middle Mississippi River: Habitat associations, population structure, and implications for conservation. Chelonian Conservation and Biology, 5: 225-231.

Bartholomew, P. 2002. "Spiny softshell turtle" (On-line). Animal Diversity Web. Accessed April 15, 2011 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Apalone_spinifera.html.

Bodie, J., R. Semlitsch, R. Renken. 2000. Diversity and structure of turtle assemblages: Associations with wetland characters across floodplain landscape. Ecography, 23: 444-456.

Browne, C., S. Hecnar. 2007. Species loss and shifting population structure of freshwater turtles despite habitat protection. Biological Conservation, 138: 421-429.

Degenhardt, W., C. Painter, A. Price. 1996. Amphibians and reptiles of New Mexico. Albuquerque, New Mexico: University of New Mexico Press.

Doody, J. 1996. Summers with softshells. Bulletin of Chicago Herpetological Society, 31: 132-133.

Ernst, C., R. Barbour. 1972. Turtles of the United States. Lexington, Kentucky: University Press Kentucky.

Ernst, C., R. Barbour. 1989. Turtles of the World. Washington D.C.: Smithsonian Institution Press.

Ernst, C., R. Barbour, J. Lovich. 1994. Turtles of the United States and Canada. Washington D.C.: Smithsonian Institution Press.

Ernst, C., J. Lovich. 2009. Turtles of the United States and Canada. Baltimore, Maryland: The John Hopkins University Press.

Ewert, M. 1985. Embryology of turtles. Pp. 75-268 in C Gans, F Billett, P Maderson, eds. Biology of the Reptilia, Vol. 14. New York, New York: John Wiley and Sons.

Fitch, H., M. Plummer. 1975. A preliminary ecological study of the soft-shelled turtle Trionyx muticus in the Kansas River. Israel Journal of Zoology, 24: 28-32.

Hulse, A., C. McCoy, E. Censky. 2001. Amphibians and reptiles of Pennsylvania and the Northeast. Ithaca, New York: Cornell University Press.

Jackson, D., J. Allen, P. Strupp. 1976. The contribution of non-pulmonary surfaces to CO2 loss in 6 species of turtles at 20 C. Comparative Biochemistry and Physiology, 55A: 243-246.

Lindeman, P. 2000. Resource use of five sympatric turtle species: Effects of competition, phylogeny, and morphology. Canadian Journal of Zoology, 78: 992-1008.

Minnesota Department of Natural Resources, 2011. "Apalone mutica" (On-line). Minnesota Department of Natural Resources. Accessed April 03, 2011 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=ARAAG01020.

Moll, E., D. Moll. 2000. Conservation of river turtles. Pp. 126-155 in M Klemens, ed. Turtle Conservation. Washington D.C.: Smithsonian Institution Press.

Nagle, R., M. Plummer, J. Congdon, R. Fischer. 2003. Parental investment, embryo growth, and hatchling lipid reserves in softshell turtles (Apalone mutica) from Arkansas. Herpetologica, 59: 145-154.

Oldfield, B., J. Moriarty. 1994. Amphibians & Reptiles Native to Minnesota. Minneapolis, Minnesota: University of Minnesota Press.

Pappas, M., J. Congdon, A. Pappas. 2001. Weaver Bottoms 2001 turtle survey: management and conservation concerns. Nongame Wildlife Survey, Minnesota Department of Natural Resources and U.S. Fish and Wildlife Service.

Plummer, M. 1977. Activity, habitat, and population structure in the turtle, Trionyx muticus. Copeia, 3: 431-440.

Plummer, M. 1976. Some aspects of nesting success in the turtle, Trionyx muticus. Herpetologica, 32: 353-359.

Plummer, M., D. Farrar. 1981. Sexual dietary differences in a population of Trionyx muticus. Journal of Herpetology, 15: 175-179.

Plummer, M., H. Shirer. 1975. Movement patterns in a river population of the softshell turtle Trionyx muticus. University of Kansas Museum of Natural History Occasional Papers, 43: 1-26.

Quammen, R. 1992. A latest Cretaceous (Maestrictian) lower vertebrate faunule from the Hell Creek Fromation of North Dakota. Proceedings of the North Dakota Academy of Science, 46: 41.

Snider, A., J. Bowler. 1992. Longevity of Reptiles and Amphibians in North American Collections. Pp. 1-44 in J Collins, ed. Herpetological Circular, Vol. 21. Utah: Society for the Study of Amphibians and Reptiles.

Stone, P., J. Iverson. 1999. Cutaneous surface area in freshwater turtles. Chelonian Conservation and Biology, 3: 512-515.

Trauth, S., H. Robison, M. Plummer. 2004. The amphibians and Reptiles of Arkansas. Fayetville: University of Arkansas Press.

Vogt, R. 1981. Natural History of Amphibians and Reptiles of Wisconsin. Wisconsin: Milwaukee Public Museum.

Watermolen, D. 2004. Softshell turtles (g. Apalone) as bald eagle prey. Bulletin of Chicago Herpetological Society, 39: 69-70.

van Dijk, P. 2010. "Apalone mutica" (On-line). In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.1. Accessed July 05, 2011 at http://www.iucnredlist.org/apps/redlist/details/165596/0.

 
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Albers, J. 2012. "Apalone mutica" (On-line), Animal Diversity Web. Accessed August 01, 2014 at http://www.biokids.umich.edu/accounts/Apalone_mutica/

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