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Sternotherus carinatusRazorback Musk Turtle

By Chelsea Mossburg

Geographic Range

Razor-back musk turtles (Sternotherus carinatus) have a small geographic range which is limited to the south central United States. They are found in six states: southeastern Oklahoma, eastern Texas, southern Mississippi and Arkansas, nearly the entire state of Louisiana, and a small area of southwestern Alabama. The range does not include coastal wetlands because these turtles primarily use freshwater habitats. Razor-back musk turtles can be found from the Brazos River in Texas to the Pascagoula River in Mississippi. They were also found in the Kiamichi, Mountain Fork, Little, and Red rivers in Oklahoma. (Ernst, et al., 1997; Lindeman, 2008; Riedle, et al., 2009; van Dijk, 2013)

Habitat

Razor-back musk turtles frequent medium to large flowing streams and rivers, and are sometimes found in swamps and lakes. They have been associated with bodies of water that have sandy or rocky substrates with low turbidity. Sites with more deadwood and aquatic vegetation are beneficial for the turtles for basking. Individuals tend to sit high above the water on deadwood while basking. (Ernst, et al., 1997; Lindeman, 2008; van Dijk, 2013)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams

Physical Description

The scutes of the carapace range from light brown to orange with dark streaks that typically fade with age. The carapace is ovoid and slopes upward to make a triangular high-domed shell (typically 16 cm in height) with a medial keel (medial ridge on the vertebral scutes). Because of the triangular shape, there is overlap between the vertebral scutes. Carapace length ranges between 10.2 and 11.7 cm.

The plastron is yellowish in color and it lacks a gular scute (located in the anterior part of the shell, close to the head), which gives it only ten plastral scutes instead of eleven. The plastron is reduced and weakly hinged between the abdominal and pectoral scutes, and there is also a small anal notch.

The skin color ranges from gray to pink to light brown with small dark spots and the slightly hooked jaws have small dark streaks on them. S. carinatus have a pair of barbels on the chin and their heads are moderately sized with tubular snouts.

Males are distinguished by possessing longer and thicker tails and rough patches of scales on their thighs and hind limbs. There is little other sexual dimorphism although males can be slightly larger than females in size. (Ernst, et al., 1997; Franklin, 2015; LaDuc and Cannatella, 2014; Lindeman, 2008)

  • Sexual Dimorphism
  • male larger
  • Range length
    10.2 to 11.7 cm
    4.02 to 4.61 in

Development

The eggs are white, elliptical and have brittle shells. The incubation period is 110 to 120 days. Offspring sex is determined via temperature-dependent sex determination with males being produced at intermediate temperatures and females at either cooler and warmer temperatures. In an experimental study, all males were produced when incubated at 27 degrees Celsius, and all females were produced when incubated below 22 or above 30 degrees Celsius. (Ernst, et al., 1997; Iverson, 2002; Lindeman, 2008)

  • Development - Life Cycle
  • temperature sex determination

Reproduction

Sternotherus carinatus courtship and mating acts appear to be identical to S. odoratus and happen in three phases. The tactile phase is when the male extends his head, approaches another turtle from behind and smells the tail to determine the gender. If the turtle is female, the male moves to her side and he nudges her bridge with his nose. The mounting phase is when the male positions his plastron directly over the female carapace and grasps its margins with all four clawed feet. The male moves the female’s tail to gain access to the cloaca. During coital positioning, the male extends his head and starts rubbing and biting the female’s head. The number of mates an individual has is not known. (Edmonds, 2002; Ernst, et al., 1997; Ernst, et al., 2014; Iverson, 2002; LaDuc and Cannatella, 2014)

Females reach maturity around 10 cm carapace lengths which corresponds to about four to five years of age. Males reach maturity between 10 to 12 cm carapace lengths which corresponds to about five to six years of age. As they age, the carapacial scutes have dark streaks that fade.

Female razor-back musk turtles have ovulatory-sized follicles in late April to early July and male spermatogenesis occurs from June to August. Courtship and mating occur in the spring and the nesting season is from May to June, but may occur earlier in the southern part of their range. Females can lay two to three clutches per season (one to seven eggs). As mentioned above, the incubation period lasts three to four months followed by hatching during August and September. S. odoratus females are able to store sperm from the previous fall throughout winter, and this also may be true regarding S. carinatus. Hatchlings typically have carapace lengths of 23 to 31 mm. (Edmonds, 2002; Ernst, et al., 2014; Iverson, 2002; LaDuc and Cannatella, 2014)

  • Breeding interval
    Females can lay 2-3 clutches per season
  • Breeding season
    Nesting occurs from May to June, but may be earlier in individuals that live more southward
  • Range number of offspring
    1 to 7
  • Range gestation period
    110 to 120 days
  • Range age at sexual or reproductive maturity (female)
    4 to 5 years
  • Range age at sexual or reproductive maturity (male)
    5 to 6 years

Other than yolk provisioning by females, there is no parental care following nest construction and oviposition. Males have no role after mating. (Ernst, et al., 1997; Iverson, 2002; Lindeman, 2008)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

The exact life span of razor-back musk turtles in the wild is unknown but in captivity, they typically live 20 years with the longest lifespan recorded at 29 years. (Franklin, 2015)

  • Range lifespan
    Status: captivity
    29 (high) years
  • Average lifespan
    Status: captivity
    20 years

Behavior

Razor-back musk turtles are a diurnal species with activity concentrated in the morning and in the late afternoon. Compared to other musk turtles, this species spends more time basking above the water on woody debris. While they are in the water, the turtles use submerged deadwood, rocks or crevices for hiding.

Individuals that live in the more southern parts of the range are active for longer periods of the year. These turtles are aquatic hibernators and the capacity for freeze tolerance is not as well developed as that found in terrestrial hibernators. (Constanzo, et al., 2001; Franklin, 2015; LaDuc and Cannatella, 2014; Lindeman, 2008)

Home Range

Home ranges for the species are not known. (Ernst, et al., 1997; Lindeman, 2008; van Dijk, 2013)

Communication and Perception

During mating, a male turtle will advance on another turtle from behind in order to smell it and determine the sex of the turtle. The barbels on the chin are thought to be a sensory organ used for helping the turtle find prey in muddy substrate. Other than the perception of mates and the potential use of the barbels, little else is known about razor-back musk turtle communication and perception. (Ernst, et al., 2014; Muskturtle.co.uk, 2015)

Food Habits

Sternotherus carinatus feeds mainly in the water. The species' eating habits are omnivorous with a diet that consists of insects, seeds, carrion, crustaceans, amphibians, and aquatic plants. One study (Atkinson 2013) found that adults of this species tend to favor mollusks as they grow larger, such as the Asian clam (Corbicula fluminea) which is an invasive species. In areas where the Asian clam populations are high, it makes up the majority of their diet, but the diet is more varied in other areas. (Atkinson, 2013; Lindeman, 2008)

  • Animal Foods
  • amphibians
  • carrion
  • insects
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • Plant Foods
  • seeds, grains, and nuts

Predation

Like most turtles, eggs and hatchlings suffer the most predation, but adults of this species are small enough to be preyed on as well. Eggs are eaten by raccoons (Procyon lotor) and skunks (Mephitis). Hatchlings and juveniles are vulnerable to a wide array of aquatic predators including predacious diving beetles (Dystiscidae), freshwater bass (Micropterus), bullfrogs (Lithobates catesbeianus), snakes like kingsnakes (Lampropeltis getula) and cottonmouths (Agkistrodon piscivorus), and birds of prey such as crows (Corvus) and bald eagles Haliaeetus leucocephalus. Adults may be preyed on by alligators. Individuals of this species have been observed in the lab to retreat from water from an alligator snapping turtle (Macrochelys temminckii) enclosure, so alligator snappers are probably a significant predator too. Humans fishing sometimes take this species by accident, and often kill it when they do.

Musk turtles get their common name from the strong and unpleasant smelling secretions produced by glands along the bridge (the section of the shell where the upper and lower portions meet). These secretions probably discourage some predators. (Franklin, 2015; Lindeman, 2008)

Ecosystem Roles

Razor-back musk turtles are intermediate predators in foodwebs, serving as both predator and prey. They are omnivores and they feed on insects, mollusks, crustaceans, and vegetation. Their diet consists of what is readily available to them. They are known to be hosts to some parasites, including a blood protozoan, a nematode, and several trematodes. (Atkinson, 2013; Lindeman, 2008)

Commensal/Parasitic Species
  • blood protozoans, nematodes

Economic Importance for Humans: Positive

Razor-back musk turtle hatchlings are caught and the sold in the commercial pet trade. These turtles are quite popular especially in Europe and it is estimated that around 50,000 individuals were shipped to the European Union between 2008 and 2012. However, during 2002 to 2005, there were only around 900 individuals exported from the United States suggesting that their popularity recently increased. ("Southern and Midwestern Turtle Species Affected by Commercial Harvest", 2005; Kopecký, et al., 2013)

Economic Importance for Humans: Negative

There are no known adverse effects of S. carinatus on humans.

Conservation Status

Sternotherus carinatus has been evaluated by the International Union for Conservation of Nature (IUCN), and their abundant populations result in its listing in the category of Least Concern. While populations appear to be stable, potential risks include habitat destruction, polluted water, and deadwood removal. They are also regarded as fifth most vulnerable species of turtle in commercial pet trade. (Lindeman, 2008; van Dijk, 2013)

Contributors

Chelsea Mossburg (author), Indiana University - Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne.

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.

carrion

flesh of dead animals.

chemical

uses smells or other chemicals to communicate

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

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.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

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.

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.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

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.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

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

Center for Biological Diversity. 2005. "Southern and Midwestern Turtle Species Affected by Commercial Harvest" (On-line). Biological Diversity. Accessed April 03, 2015 at http://www.biologicaldiversity.org/campaigns/southern_and_midwestern_freshwater_turtles/pdfs/Southern-and-midwestern-turtle-species-affected-by-harvest.pdf.

Atkinson, C. 2013. Razor-Backed Musk Turtle (Sternotherus carinatus) Diet Across a Gradient of Invasion. Herpetological Conservation and Biology, 8/3: 561-570. Accessed June 26, 2015 at http://www.herpconbio.org/Volume_8/Issue_3/Atkinson_2013.pdf.

Constanzo, J., J. Litzgus, J. Iverson, R. Lee Jr.. 2001. Cold-Hardiness and Evaporative Water Loss in Hatchling Turtles. Physiological and Biochemical Zoology, 74/4: 510-519.

Edmonds, J. 2002. "Stinkpot Sternotherus odoratus" (On-line). Sara Registry. Accessed April 05, 2015 at http://www.sararegistry.gc.ca/virtual_sara/files/cosewic/sr_stinkpot_e.pdf.

Ernst, C., R. Altenburg, R. Barbour. 1997. "Sternotherus carinatus" (On-line). Turtles of the World. Accessed March 20, 2015 at http://wbd.etibioinformatics.nl/bis/turtles.php?selected=beschrijving&menuentry=soorten&id=229.

Ernst, C., R. Altenburg, R. Barbour. 2014. "Sternotherus odoratus" (On-line). Turtles of the World. Accessed April 05, 2015 at http://wbd.etibioinformatics.nl/bis/turtles.php?menuentry=soorten&id=226.

Franklin, C. 2015. "Razorback Musk Turtle (Sternotherus carinatus)" (On-line). Texas Turtles. Accessed April 03, 2015 at http://www.texasturtles.org/sternotherus_carinatus.html.

Iverson, J. 2002. Reproduction in Female Razorback Musk Turtles (Sternotherus carinatus: Kinosternidae). The Southwestern Naturalist, 47/2: 215-224.

Kopecký, O., L. Kalous, J. Patoka. 2013. Establishment risk from pet-trade freshwater turtles in the European Union. Knowledge and Management of Aquatic Ecosystems, 410: Article 2. Accessed June 27, 2015 at http://dx.doi.org/10.1051/kmae/2013057.

LaDuc, T., D. Cannatella. 2014. "Musk Turtles" (On-line). Herps of Texas. Accessed April 05, 2015 at http://www.herpsoftexas.org/category/organismtype/turtles/musk-turtles.

Lindeman, P. 2008. Sternotherus carinatus (Gray 1856) - Razorback Musk Turtle, Razor-Backed Musk Turtle. Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group, 5: 012.1-012.6. Accessed January 20, 2015 at http://www.iucn-tftsg.org/wp-content/uploads/file/Accounts/crm_5_012_carinatus_v1_2008.pdf.

Muskturtle.co.uk, 2015. "Sternotherus carinatus - The Razorback Musk Turtle" (On-line). Accessed May 14, 2015 at http://www.muskturtle.co.uk/#!carinatus/c1mdv.

Riedle, J., P. Shipman, S. Fox, D. Leslie, Jr. 2009. Habitat Associations of Aquatic Turtle Communities in Eastern Oklahoma. Proceedings of the Oklahoma Academy of Science, 89: 11-22. Accessed June 27, 2015 at http://digital.library.okstate.edu/oas/oas_pdf/v89/011-022.pdf.

van Dijk, P. 2013. "Sternotherus carinatus" (On-line). The IUCN Red List of Endangered Species Version 2015.2. Accessed March 20, 2015 at http://www.iucnredlist.org/.

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