Graptemys ernsti

Geographic Range

Graptemys ernsti (Escambia Map Turtle) occurs only in the Southern United States, in a relatively small range in the Pensacola Bay drainage system located in southern Alabama and western Florida. This includes the Escambia, Yellow, Conecuh, and Shoal Rivers. Recently, G. ernsti was found to inhabit the Pea and Choctawhatchee Rivers in Alabama, which drain into the Choctawhatchee Bay. Here, G. ernsti is sympatric with Graptemys barbouri . Researchers are not sure if the species is native to this area or was perhaps introduced via human activity. Escambia Map Turtles are apparently not found downstream in the Florida portion of the Choctawhatchee River.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Graptemys ernsti is highly aquatic, and only found in large to medium-sized rivers and streams that provide logs and deadwood for basking. Fast-moving waters are preferred. These waterways usually have gravelly or sandy bottoms. Two specific types of habitats have been described. The species can be found in rivers with steep banks that have rough substrate such as limestone and bedrock with small sandbars. These habitats do not provide many opportunities for basking. The preferred habitat is in rivers and streams with sandy banks and larger sand bars. More erosion in these habitats provides more woody debris and thus sites for basking. Although located relatively close to the Gulf of Mexico, this species does not often reside in estuaries or floodplain swamps. Instead, it prefers freshwater waterways with access to underwater retreats.

• Habitat Regions
• freshwater freshwater

• Aquatic Biomes
• rivers and streams

• Other Habitat Features
• riparian riparian

Physical Description

Escambia Map Turtles are a moderately sized, sexually dimorphic species. Adult females have an average carapace length of 27.94 cm (11 inches). Males are typically less than half the size of females with an average carapace length of 12.7 cm (5 inches). The carapace is high-domed, and triangular in the cross-section. The carapace is an olive to light-brown color with a vertebral keel. Along the vertebral keel is a broken black stripe. The keel is prominent in males and juveniles, but more rounded in adult females. The keel is most pronounced on vertebrals two and three, with the latter much lower than the first. The marginal scutes have yellow circular borders that curve inward. The pleural scutes have yellow to orange bars with black borders on the distal portion. This forms a reticulating pattern. The pale yellow plastron is hingeless, and relatively flattened in both sexes. An inconspicuous dark pattern follows the seams of the plastron, and is more pronounced on seams running horizontal to the body.

The head and limbs are a brown to olive color with yellow markings. Occasionally, these markings can be a dark yellow-orange color. An interorbital blotch on the top of the head ends anteriorly in a distinct three-pronged shape (nasal trident). Each eye has postorbital markings that end in rounded posterior edges. The interorbital blotch is not connected to the postorbital markings. Two neck stripes form oval tips at the back of the head that may separate into supraoccipital blotches. The underside of the jaw possesses medial longitudinal striping. The limbs and tail are striped.

Female Graptemys ernsti have a much larger head than males. Males have a narrow head, while a female’s head is disproportionately wide compared to her body. Males have longer tails with the vent, or cloacal opening, located nearer the tip, beyond the rear edge of the carapace. This allows the vent to extend outward far enough during copulation. Females have narrower tails, with the vent underneath the rear edge of the carapace. Large adult females may develop a humpback due to a slope of the first vertebral scute.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes shaped differently

Development

Graptemys ernsti , like all turtles, reproduces sexually, with internal fertilization. The oval, flexible-shelled eggs are deposited in an underground nest dug by the female, and are then left to incubate and hatch without further adult involvement. Sex is presumably influenced by nest temperatures (temperature-dependent sex determination; TSD), as has been demonstrated in other species of Graptemys .

• Development - Life Cycle
• temperature sex determination

Reproduction

See notes on mating behavior included in next section.

A male G. ernsti may reach sexual maturity in as few as three years, while females are not considered to be mature until about thirteen to eighteen years of age. Mating activity has been observed throughout September to November. Courtship takes place in the water. The male will swim in front of the female and vibrate his head on the female’s snout in a vertical motion. The female will withdraw her head slightly, and the male will swim behind her to begin copulation.

Females nest from late April to late July, when water levels are the highest. Eggs are usually laid in sandbars along river bends. The female will dig a small hole a few inches deep with her hind feet, and about 10 to 50 feet from the water’s edge to lay a single clutch of elliptical, soft-shelled eggs. Eggs may absorb water and later become nearly spherical. Clutch size is dependent on female carapace length. Larger females will produce larger clutches. Clutch size varies from 6 to 13 eggs; average clutch size is about 7 eggs. The average number of clutches per season laid by a single female is about four. This is also dependent on female size.

• Key Reproductive Features
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• oviparous oviparous

Graptemys ernsti females invest significant resources in yolking (provisioning) their eggs and invest energy (and entail risk) when they leave the water to seek nest sites and then dig the nest chamber and deposit and bury their eggs. But there is no parental care of eggs or young once the eggs are covered and abandoned.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning

Lifespan/Longevity

There appears to be no data on lifespan of G. ernsti , but this species was once considered conspecific with Graptemys pulchra , which is known to have lived for 15 years in captivity. In addition, the closely related Graptemys barbouri has a notable longevity record of over 31 years for a captive specimen that was acquired as an adult. It is likely that G. ernsti could live as long.

Behavior

Escambia Map Turtles are diurnal, and have been seen basking in every month of the year. They can withstand water temperatures as low as 11°C, but are generally inactive at temperatures below 19°C. They prefer to bask on sunny days when water levels are higher, and air temperatures exceed water temperature, typically in early spring. They can be found basking at any time during the day, and usually spend many hours at a time basking. Offshore basking sites are usually preferred. Deadwood near deep water is used as a basking perch most of the time. Females and juveniles have been known to bask in shaded areas as opposed to direct sunlight. Basking activity decreases in midsummer to early fall. Basking turtles are alert and shy, and drop into the water at any disturbance.

Graptemys ernsti generally becomes dormant during the colder months, from November through February, at this time sitting on the bottom or wedged among submerged rocks or trees.

• Key Behaviors
• diurnal diurnal
• motile motile

Home Range

A number of G. ernsti were displaced 24 km up or downstream from their capture point; half of recovered females returned to their capture points, but no males returned. However 42% of non-displaced males were recaptured near their original capture points (Shealy, 1976).

Communication and Perception

These turtles are presumably highly visual animals, but also appear to perceive sound and/or vibration. Use of chemical cues is possible but unknown.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• visual visual
• infrared/heat infrared/heat
• tactile tactile
• acoustic acoustic
• vibrations vibrations

Food Habits

Graptemys ernsti is carnivorous. Females are able to feed primarily on mussels, snails, and sometimes crayfish due to having wider, more powerful jaws than males. Males will also feed on mussels occasionally, but will mostly feed on fly larvae, dragonflies, snails, and beetles. Juvenile females will eat mostly insects, but will transition to mussels and snails when they reach optimal size.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• insects
• mollusks
• terrestrial worms

Predation

As in most turtle species, G. ernsti suffers significant destruction of their eggs due to nest predators such as raccoons, foxes, skunks, and fish crows. Nest-seeking females are killed by raccoons and bobcats. Hatchlings and small juveniles are vulnerable to large fish, snapping turtles ( Chelydra and Macrochelys ), and herons. Humans are serious predators of these turtles, sometimes using basking turtles as shooting targets.

Ecosystem Roles

Escambia Map Turtles are predators that presumably impact or control populations of aquatic insects and mollusks. They are, in turn, predated by numerous species of birds, mammals, and other reptiles. Aquatic turtles are also host to many parasites, both internal and external (such as leeches, Placobdella sp.).

Economic Importance for Humans: Positive

Some map turtle species are known to help control invasive mollusk species, but this aspect is presently unknown for G. ernsti . Many humans enjoy seeing these turtles, especially while basking along waterways, and thus they provide a positive aesthetic component in the environment. This species has been collected for the pet trade and perhaps for food.

• Positive Impacts
• pet trade pet trade
• food food
• ecotourism ecotourism
• controls pest population

Economic Importance for Humans: Negative

These turtles are completely harmless to human interests.

Conservation Status

As of 2011, Escambia Map Turtles are listed as "near threatened" (IUCN Red List of Threatened Species). They are losing their habitats to human expansion and water pollution; survival rates have decreased due to water pollution in certain areas brought on by nearby factories. The water pollution affects them primarily by decreasing their prey base, and thus causing them to die of starvation. Use of basking turtles as targets for firearms is deplorable, and can quickly reduce populations. Some commercial collection for the pet trade may also be affecting their numbers.

Additional Links

Encyclopedia of Life

Contributors

Marissa Tetzlaff (author), Michigan State University, James Harding (editor), Michigan State University.

References

Enders, S. 2016. "Natural history: Description and identification" (On-line). Accessed November 28, 2016 at https://theturtleroom.com/species-profiles/graptemys-ernsti/ .

Enge, K., G. Wallace. 2008. Basking survey of map turtles (Graptemys) in the Choctawhatchee and Ochlockonee Rivers, Florida and Alabama. Florida Scient. , 71(4): 310-322.

Ernst, C., J. Lovich. 2009. Turtles of the United States and Canada . Baltimore: JHU Press.

Lindeman, P. 2013. The Map Turtle and Sawback Atlas: Ecology, Evolution, Distribution, and Conservation . Norman, OK: University of Oklahoma Press.

Lovich, J., J. Godwin, C. McCoy. 2011. Graptemys ernsti Lovich and McCoy 1992 – Escambia Map Turtle. Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group A.G.J. Rhodin, P.C.H. Pritchard, P.P. van Dijk, R.A. Saumure, K.A. Buhlmann, J.B. Iverson, and R.A. Mittermeier, Eds. Chelonian Research Monographs , 51: 1-6.

Lovich, J., C. McCoy. 1992. Review of the Graptemys pulchra group (Reptilia: testudines: emydidae), with descriptions of two new species. Annals of Carnegie Museum , 61(4): 300-302.

Powell, R., R. Conant, J. Collins. 2016. A Field Guide to Reptiles and Amphibians of Eastern and Central North America, 4th Ed. . Boston: Houghton Mifflin Harcourt.

Sasser, M., J. Godwin. 2014. "Escambia Map Turtle" (On-line). Accessed October 21, 2016 at http://www.outdooralabama.com/escambia-map-turtle. .

Shealy, R. 1976. The natural history of the Alabama map turtle, Graptemys pulchra baur, in Alabama. Bull. Florida St. Mus , 21: 47-111.

Slavens, F., K. Slavens. 1999. Reptiles and Amphibians in Captivity: Breeding— Longevity and Inventory Current January 1, 1998 . Seattle, Washington: Slaveware.