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Apalone feroxFlorida Softshell Turtle

By Heather Stewart

Geographic Range

Apalone ferox is found only in the southeastern United States, from southern South Carolina west to Mobile Bay, Alabama, and south through the Florida peninsula. It is apparently not found in the Florida Keys, with the exception of a colony on Big Pine Key, where it was possibly introduced. Apalone ferox can be common over much of its range and sometimes thrives in urbanized areas. (Ashton and Ashton, 1985; Ernst, et al., 1994; Meylan, 2006; Pritchard, 1979)

Habitat

Florida softshell turtles are highly aquatic and are found in freshwater ponds, lakes, swamps, marshes, and sometimes drainage ditches. They are generally found in water bodies with muddy or sandy bottoms. Occasionally they are found in brackish waters near the mouths of streams. They can also be found in the quieter portions of rivers and streams and may sometimes occur sympatrically with spiny softshell turtles, Apalone spinifera. However Apalone spinifera prefers aquatic habitats with moving water, so is more common where A. ferox is scarce. (Bonin, et al., 2006; Conant and Collins, 1998; Ernst, et al., 1994; Meylan, 2006)

Physical Description

Adult Florida softshell turtles have bumpy, leathery, oblong carapaces with dark brown to olive green colors and a gray to white plastron. Both the carapace and plastron lack scutes. The carapace has longitudinal rows of indentations and raised areas on the dorsal surface. On the thickened edge of the anterior portion of the carapace there is a series of wide, short tubercles in a crescent shape. Short tubercles also cover the sides of the forelimbs. Carapace tubercles on Florida softshell turtles are flattened hemispheres instead of the cone-shaped projections seen in the sympatric Gulf Coast Softshell, Apalone spinifera aspera. Bones underlying the plastron can sometimes be seen through the leathery skin covering. The carapace occasionally has faint irregular blotches left over from the juvenile pattern. A yellow to red stripe sometimes is present from each eye to the base of the lower jaw. The tubular, pig-like nose is truncated with each nostril having a lateral ridge projecting from the nasal septum. All four feet are webbed; webbing extends up the shank of the hind legs. This species is bulky and the largest of all New World trionychids. Sexual dimorphism is marked, with females much larger than males. Adult females are usually between 28 and 63 centimeters in carapace length (record 73.6 cm), with short tails that barely extend beyond the carapace rim. Males are usually between 15 and 33 centimeters in carapace length, with long, thick tails with the anal vent well beyond the carapace rim. (Ashton and Ashton, 1985; Bartlett and Bartlett, 2006; Conant and Collins, 1998; Ernst, et al., 1994; Meylan, 2006; Pritchard, 1979)

Juveniles have more contrasting color patterns than adults. The carapace is olive, tan, or light brown with darker brown or black spots and a yellow marginal rim. The plastron is dark purplish gray to black. The snout and neck are marked with yellow or orange stripes. The snout is marked with a Y shaped figure on the anterior edge, reaching from each eye down the middle of the nose. (Ashton and Ashton, 1985; Conant and Collins, 1998; Ernst, et al., 1994; Meylan, 2006; Pritchard, 1979)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range mass
    43.6 (high) kg
    96.04 (high) lb
  • Range length
    15 to 73.6 cm
    5.91 to 28.98 in

Development

Sex determination is genetic, with no influence from nest temperature. Hatchlings and juveniles are shaped much like adults, although their color darkens with age. Growth slows with maturity. (Ernst, et al., 1994; Meylan, 2006)

Reproduction

Most (more than 90%) of mature females appear to breed every year. In Florida females carried eggs in the oviduct from March through July; males were found to produce sperm in fall (September to October) and mating probably occurs in spring (March to May). Although Florida softshell turtles are fairly common, courtship and mating have not been described in the literature. (Ernst, et al., 1994; Iverson and Moler, 1997; Meylan, 2006)

Nesting takes place between mid March and July in central and southern Florida, and in June and July further north. There is a possibility for females to nest 2 to 7 times in one season. Florida softshell turtles may produce more eggs per year (up to 225) than any reptile species other than South American river turtles (Podocnemis expansa), some of the marine turtles, or some Asian softshell species. Females emerge from the water in daytime to nest in sand or well drained soil, but sometimes use newly constructed alligator nests. This habit may take advantage of the female alligator's defense of her nest against predators. The nest is dug with the hind feet and may be up to 14 cm deep and 10 cm in diameter. The female may expel cloacal water on the nest site, perhaps to facilitate excavation. After nesting, females often scratch and churn the ground as they move away from the nest. This behavior may draw predators away from the actual nest. From 9 to 24 brittle, white, spherical eggs are laid per clutch; eggs have an average mass of about 14 grams and range from 24 to 33 mm in diameter. The incubation period is between 56 and 80 days, with the hatchlings averaging 9.7 g and ranging from about 29 to 44 mm in carapace length. Florida softshell turtles are sexually dimorphic with females exceeding the largest male's size by three to five times. (Ernst, et al., 1994; Iverson and Moler, 1997; Meylan, 2006; Pritchard, 1979)

The minimum size for sexual maturity in males is about 0.7 kg and 15.1 cm in plastron length (PL) Some may mature at as small a size as 12 cm PL. For females, the minimum size for sexual maturity is about 20 cm in plastron length. However most females may mature at about 24 cm PL, and some may need to reach 30 cm PL before reproducing. (Meylan, 2006)

  • Breeding interval
    Females can lay up to 7 clutches per year between February and August.
  • Breeding season
    Breeding occurs from February to August, although most breeding occurs from March to July.
  • Range number of offspring
    9 to 40
  • Average number of offspring
    26
  • Range gestation period
    56 to 80 days

Energy is concentrated by the female in the yolk of her eggs, and the production of several egg clutches, along with the nesting process itself, is energetically demanding. Once the female leaves the nest site, there is no further parental investment in the eggs or young. (Ernst, et al., 1994; Meylan, 2006)

  • Parental Investment
  • no parental involvement
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

The average and maximum lifespan of Apalone ferox in the wild appears to be unknown. Captives often live over 20 years and a specimen at the National Zoological Park (Washington D.C.) reportedly lived 36 years and 8 months. (Ernst, et al., 1994; Slavens, 1999)

  • Range lifespan
    Status: captivity
    36.75 (high) years
  • Typical lifespan
    Status: captivity
    20 (high) years

Behavior

Florida softshell turtles are almost entirely aquatic, but can move fast both in water and on land. They are commonly seen basking in the sun on logs or muddy banks or in floating vegetation. They also spend much of their time buried in the sand or soft mud of their habitats. Florida softshell turtles are known for being extremely aggressive and will snap or scratch at anything within reach with their sharp jaws and claws if they are handled or feel threatened. The specific name "ferox" means "ferocious." Apalone ferox can also excrete a foul smelling musk to warn away predators. Other softshell turtle species display occasional intraspecific aggression and large animals may dominate smaller ones in captivity. (Ashton and Ashton, 1985; Ernst, et al., 1994; Meylan, 2006)

Perhaps more than other softshell turtle species, Florida softshell turtles are willing to move overland to seek better conditions, sometimes leading to mortality on roads. Florida softshell turtles can tolerate the high temperatures found in their shallow water habitats. Maximum tolerated temperatures reported for this species ranged from 38.9 to 42.3 degrees C. These turtles can be active all year when temperatures are mild, but become inactive during cold weather. In the northern part of their range they will hibernate during the coldest part of the winter. Florida softshell turtles tolerate long submergence times in water, especially when they are inactive and the water is cold and high in oxygen. Gas exchange can occur through the skin and perhaps through cloacal membranes. (Ernst, et al., 1994; Meylan, 2006)

Home Range

Little seems to be known about home range or territoriality in this species. (Ernst, et al., 1994)

Communication and Perception

Little has been reported about communication and perception in Florida softshell turtles. Another American softshell turtle, Apalone spinifera, was reported to have some orientation ability for migratory movement; orientation seemed to be dependent on solar (sun) cues coupled with an internal time sense. Hatchlings oriented towards light and (unseen) water. Color vision seems likely in softshell turtles. (Ernst, et al., 1994)

  • Communication Channels
  • visual

Food Habits

Florida softshell turtles are mostly carnivorous, and both predaceous and scavenging. Typical foods include snails, insects, crustaceans, fish, amphibians, small turtles (Pseudemys, Sternotherus), snakes (Nerodia, Regina), and occasional aquatic birds. Vegetation and seeds sometimes occur in stomach contents. Small Florida softshell turtles eat many insects, but increase the number of snails and fish in the diet as they grow. Males may consume more snails, clams, and palm seeds than females, which may prefer fish or larger items. Florida softshell turtles conceal themselves in the sand at the bottom of lakes and ambush passing schools of fish. Perhaps because they eat carrion, Florida softshell turtles may be be more effected by pesticides than other aquatic turtles. (Bonin, et al., 2006; Ernst, et al., 1994; Meylan, 2006)

  • Animal Foods
  • birds
  • amphibians
  • reptiles
  • fish
  • carrion
  • insects
  • mollusks
  • terrestrial worms
  • aquatic crustaceans
  • Plant Foods
  • leaves
  • seeds, grains, and nuts
  • algae

Predation

Crows, spotted skunks, American black bears, raccoons, and red foxes all rob Florida softshell turtle nests. Large fish, turtles (Chelydra, Macroclemys), snakes (Agkistrodon, Nerodia), raptorial birds (Everglades kites, eagles) wading birds (herons and egrets) and mammals (armadillos, striped skunks, and otters) eat young turtles, and alligators feed on Florida softshell turtles of all sizes. Humans are the greatest predator of all - people exploit these turtles for food and pets, destroy and pollute habitat, and cause highway mortality. (Bonin, et al., 2006; Ernst, et al., 1994; Meylan, 2006)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Florida softshell turtles play a role in the aquatic ecosystem both as predators and as scavengers, and in turn provide food (as eggs and post-hatching turtles) for other predators. Young Apalone ferox are prone to bacterial and fungal skin problems; these problems occur in both wild and captive animals and populations. Little is known about parasites in Apalone ferox; they can harbor leeches, and Foster et al. (1998) found eight helminth species in Florida softshell turtle obtained from a commercial processor. The most prevalent helminths were Spiroxys amydae (80%), Cephalogonimus vesicaudus (80%), Vasotrema robustum (76%) and Proteocephalus (63%). (Bartlett and Earle-Bridges, 1996; Ernst, et al., 1994; Foster, et al., 1998)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Florida softshell turtles are harvested in large numbers for the food trade, both for domestic consumption and, increasingly, to supply Asian markets. Between July 1990 and July 1991, 3600 softshell turtles were purchased for meat in south Florida. Today there are breeding centers in southern Florida to raise turtles for Chinese markets (Bonin et al., 2006), but wild turtles are often taken to resupply breeding farms. Apalone ferox is the most heavily harvested turtle species in Florida. (Bonin, et al., 2006; Ernst, et al., 1994; Meylan, 2006; Moll and Moll, 2004)

Economic Importance for Humans: Negative

Florida softshell turtles are generally harmless to human interests; they do eat fish and occasionally young water birds, but no significant effects on prey populations have been reported.Florida softshell turtles are aggressive and will bite if handled or restrained, but are probably harmless to humans if left alone. (Bartlett and Bartlett, 2006; Ernst, et al., 1994)

Conservation Status

Florida softshell turtles remain common in many parts of their range, but populations are locally threatened due to habitat destruction and heavy harvesting. Despite large numbers removed from the wild in some places, Florida softshell turtles remain common in refuge areas and other areas less subject to harvest; their dispersal abilities may allow them to repopulate over-harvested or isolated habitats. Softshell turtles (Apalone) are sensitive to rotenone, a poison often used to collect and survey fish for population studies. Florida softshell turtles are subject to harvest regulations in states where they occur, but are not yet considered to be endangered or threatened on any Federal or State list. They are a Species of Concern in South Carolina. Unusual among turtles in general, Florida softshell turtles may be able to sustain a regulated harvest, and thus take pressure off more sensitive species (Meylan 2006). (Ernst, et al., 1994; Meylan, 2006)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Heather Stewart (author), Michigan State University, James Harding (editor, instructor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

hibernation

the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scavenger

an animal that mainly eats dead animals

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

sperm-storing

mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

References

Ashton, R., P. Ashton. 1985. Handbook of Reptiles and Amphibians of Florida part two: Lizards, Turtles and Crocodilians. Miami, Florida: Windward Publishing Inc..

Bartlett, P., M. Earle-Bridges. 1996. Turtles and Tortoises: Everything about Selection, Care, Nutrition, Breeding, and Behavior. Hong Kong: Barron's Educational Series, Inc.

Bartlett, R., P. Bartlett. 2006. Guide and Reference to the Crocodilians, Turtles, and Lizards of Eastern and Central North America. Gainesville: University Press of Florida.

Bonin, F., B. Devaux, A. Dupré. 2006. Turtles of the World. Baltimore: The Johns Hopkins University Press.

Conant, R., J. Collins. 1998. Reptiles and Amphibians Eastern/Central North America. Boston: Houghton Mifflin Company.

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

Foster, G., J. Kinsella, P. Moler, L. Johnson, D. Forrester. 1998. Parasites of Florida Softshell Turtles (Apalone ferox) from Southeastern Florida. Journal of the Helminthological Society of Washington, 65 (1): 62-64.

Iverson, J., P. Moler. 1997. The female reproductive cycle of the Florida softshell turtle (Apalone ferox). Journal of Herpetology, Vol. 31: 399-409.

Meylan, P. 2006. Biology and Conservation of Florida Turtles. St. Petersburg, Florida: Chelonian Research Foundation.

Moll, D., E. Moll. 2004. The Ecology, Exploitation, and Conservation of River Turtles. New York: Oxford University Press.

Pritchard, P. 1979. Encyclopedia of Turtles. New Jersey: T. F. H. Publications, Inc.

Slavens, F. 1999. Reptiles and Amphibians in Captivity-Breeding-Longevity and Inventory. Seattle, WA: Slavewear.

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