Graptemys barbouriBarbour's Map Turtle

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Geographic Range

Barbour’s map turtles (Graptemys barbouri) are found in the southeastern United States, specifically in the Apalachicola and the Chipola Rivers and their tributaries in Alabama, Georgia, and the Florida panhandle. (Cagle, 1952)

Habitat

Barbour’s map turtles live almost all of their lives in large freshwater systems with limestone bottoms. They leave the water only to lay eggs and bask in the sun on large fallen branches and other accessible areas. They prefer deeper and faster flowing waters than other turtles in the family Emydidae. Females are normally found in deeper water than males, hatchlings and juveniles tend to stay closer to the riverbank than adults. (Cagle, 1952; Ernst, et al., 1994)

  • Aquatic Biomes
  • rivers and streams

Physical Description

Barbour's map turtles have dark brown or black skin with light yellow to green markings. The head is broad, with patterns specific to the species. The top of the head has a large interorbital blotch connected by a branch to the postorbital blotches and to a point just under the eye. A y-shaped pattern is found behind the orbits. There is also a light bar on the chin that follows the curve of the jaw. The top part of the neck has relatively wide stripes that are mostly of equal size. The hind limbs and tail are striped as well. (Ernst, et al., 1994)

The carapace, or dorsal part of the shell, is not smooth and rounded but highly domed. It has a prominent vertebral keel, with laterally compressed dark spines on each vertebral scute. The second and third spines are most pronounced and wear down as the turtle ages. A lower longitudinal keel is seen on the scutes beside the vertebral keel. These scutes also have C-shaped yellow markings. The overall color of the carapace is green to olive green. The plastron, or ventral part of the shell, is yellow and without markings other than a black border on the edge of each scute. A distinguishing feature of the plastron is the ridge on the abdominal and pectoral plates where they connect to the bridge. (Ernst, et al., 1994)

Sexual dimorphism is present in Barbour's map turtles. Females are much larger than males. Females have a carapace that is 15 to 33 cm long at sexual maturity, whereas mature males have a 9 to 14 cm carapace. Therefore, females can be up to three times the size of males. Females also have much wider heads than males, along with a lower jaw that extends past the upper jaw. (Cagle, 1952; Orenstein, 2001)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    4 to 33 cm
    1.57 to 12.99 in

Development

Fertilized eggs of Barbour's map turtles have a shell that surrounds a yolk sac and the developing turtle. The young develop inside of the egg until they are capable of breaking through the shell to emerge as hatchlings, which takes about 58 days. After emerging from the eggs, hatchlings dig their way out of the nest cavity and walk to the nearby stream or river. Hatchlings and juveniles are identical to adults, except that coloring is less developed and less bright, and they are much smaller in size. Hatchlings have a mean carapace length of 37 mm and mean mass of 10.7 g. (Cagle, 1952; Ernst, et al., 1994; Valenzuela and Lance, 2004; Wyneken, et al., 2008)

Their sex is determined by the temperature at which the eggs incubate, not by chromosomes like in humans. Eggs at 25 degrees Celsius produce only males, whereas eggs at 30 degrees Celsius produce only females. Females sexually mature in 15 to 20 years, while males mature in 2 to 4 years, which may have be explained by size differences in adult males and females. The development of the carapace to adult size is dependent on fontanels, which are spots filled with cartilage that allow the carapace room to grow. Males and females of the same size show differences in their fontanels. Females have a large number of fontanels, which allow for growth of the shell, whereas males have few or no fontanels. (Cagle, 1952; Ernst, et al., 1994; Valenzuela and Lance, 2004; Wyneken, et al., 2008)

  • Development - Life Cycle
  • temperature sex determination

Reproduction

Male and female Barbour's map turtles reproduce sexually, but the specific mating system is not known. Males attract females by approaching them with their neck extended in an attempt to be face-to-face. The male then undertakes a courtship routine in which he touches the sides of the female’s head with the inner surfaces of his front legs for a few seconds. (Ernst, et al., 1994)

Fertilization takes place inside the female after the male deposits sperm. The eggs are later deposited in a nest next to a stream or river. The nest cavity is excavated by the female using her hind limbs. Once the eggs are deposited, the opening to the nest is covered with dirt and the eggs are left to finish development. The nesting season for Barbour's map turtles lasts from June through early August. But nesting will occur during the winter when individuals are held in captivity. Clutch size is between 6 and 11 eggs, and a female can lay eggs up to four times in one mating season, allowing the possibility of a female laying between 11 and 51 eggs in one season. The average size of an egg is 3.71 cm long and 2.61 cm wide. (Cagle, 1952; Ernst, et al., 1994)

  • Breeding interval
    Barbour's map turtles breed annually, and females are capable of producing multiple clutches in a single mating season.
  • Breeding season
    Nesting season is June through early August.
  • Range number of offspring
    6 to 11
  • Average gestation period
    58 days
  • Range age at sexual or reproductive maturity (female)
    15 to 20 years
  • Range age at sexual or reproductive maturity (male)
    2 to 4 years

Barbour's map turtles are like many reptiles in that there is little parental investment. The male courts the female to mate with her. Once his sperm is deposited he no longer invests time or energy in the young. The female digs a nest in which to deposit eggs and covers it with dirt. Once the nesting is complete, the female leaves the eggs and does not invest further time or energy in the offspring. (Buhlmann, et al., 2008; Ernst, et al., 1994)

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

Lifespan/Longevity

There is no information about the lifespan of Barbour's map turtles in the wild. The longest observed lifespan in captivity was 31 years 8 months and 9 days at the National Zoo in Washington, DC. (Ernst, et al., 1994)

  • Range lifespan
    Status: captivity
    31 (high) years

Behavior

Because Barbour's map turtles spend most of their lives in the water, they are good swimmers. Females tend to spend more time in turbulent water than males, which may be due to the large difference in size between the sexes. They spend a large amount of their time basking in full sun on limestone edges, vines, and trees in or near the water. When the streams and rivers in which they live flood, Barbour's map turtles move to where the current is weakest in the river. (Cagle, 1952; Ernst, et al., 1994)

Home Range

The average home range is 365 meters longitudinally within the stream for males and 273 meters within the stream for females. (Ernst, et al., 1994)

Communication and Perception

Males engage in a courtship routine in which they touch the face of females with their legs, but communication and perception are otherwise largely unknown for Barbour's map turtles. (Ernst, et al., 1994)

Food Habits

All Barbour's map turtles are carnivorous. Females eat only mollusks as adults, primarily snails and some clams. The beak crushes these mollusks and all parts, including the shell, are swallowed. Males do not eat as many snails or clams as females, instead feeding more on insects and insect larvae. Hatchlings and juveniles eat insects and insect larvae before moving on to hard-shelled mollusks. (Ernst, et al., 1994; Orenstein, 2001)

  • Animal Foods
  • insects
  • mollusks

Predation

Barbour's map turtle nests are subject to predation by snakes and terrestrial mammals, such as raccoons. Humans sometimes consume Barbour's map turtles as food. Barbour's map turtles are capable of withdrawing into their shells as well as trying to bite if they are unable to escape danger. (Ernst, et al., 1994)

Ecosystem Roles

Barbour's map turtles are important predators of mollusks in the areas the inhabit and are preyed on by other predators as eggs, young, and sometimes as adults.

Economic Importance for Humans: Positive

Barbour's map turtles used in a study that isolated the first pure Flavobacterium meningosepticum, which is a cause of meningitis in humans. These turtles are also consumed by humans and sometimes kept as pets. (Ernst, et al., 1994; Jacobson, et al., 1989)

Economic Importance for Humans: Negative

There are no known adverse effects of Barbour's map turtles on humans.

Conservation Status

Barbour's map turtles are considered "vulnerable" by the IUCN and are on Appendix III of CITES. They are given a global rank of "G2," indicating that the species is imperiled. Barbour's map turtles have a relatively restricted range and are subject to threats to their freshwater ecosystems, including dredging, water impoundment, and pollution. (van Dijk, 2012)

Contributors

Gina Vasseur (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor, Catherine Kent (editor), Special Projects.

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.

carnivore

an animal that mainly eats meat

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

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

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.

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).

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.

riparian

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

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

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).

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

References

Buhlmann, K., T. Tuberville, W. Gibbons. 2008. Turtles of the Southeast. Athens, Georgia: University of Georgia.

Cagle, F. 1952. The Status of the Turtles Graptemys pulchara Baur and Graptemys barbouri Carr and Marchand, with Notes on Their natural History. Copeia, 4: 223-234.

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

Ferri, V. 2002. Turtles and Tortoises. Spain: Firefly Books.

Jacobson, E., C. Gardiner, S. Barten, D. Burr, A. Bourgeois. 1989. Flavobacterium meningosepticum infection of a Barbour's Map Turtle (Graptemys barbouri). Journal of Zoo and Wildlife Medicine, 20/4: 474-477.

Orenstein, R. 2001. Turtles, Tortoises and Terrapins Survivors in Armor. Canada: Firefly Books.

Valenzuela, N., V. Lance. 2004. Temperature Dependent Sex Determination in Vertebrates. Washington D.C: Smithsonian Institution Scholarly Press.

Wyneken, J., M. Godfrey, V. Bels. 2008. Biology of Turtles. United States: CRC Press.

van Dijk, P. 2012. "Graptemys barbouri" (On-line). IUCN Red List of Threatened Species. Accessed November 01, 2012 at http://www.iucnredlist.org/details/9496/0.