Common map turtle (Graptemys geographica)

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Common map turtle
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The common map turtle was named for the markings on its shell, which were thought to resemble a geographic map.
  • To survive hibernating underwater, the common map turtle is able to take in oxygen through its skin.
  • Common map turtles bask in groups in the summertime, with females sometimes piling upon each other to make the most of space.
  • The common map turtle is a very wary species, and disappears into the safety of water at the slightest disturbance.
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Common map turtle fact file

Common map turtle description

KingdomAnimalia
PhylumChordata
ClassReptilia
OrderTestudines
FamilyEmydidae
GenusGraptemys (1)

The common map turtle (Graptemys geographica) is a moderate-sized species of turtle that exhibits sexual dimorphism, with females reaching larger sizes than the males (2) (4) (5). The females are broad-headed and have a rounded carapace, while males have an oval carapace and long, thick tails (2) (5). The colour of the carapace is olive-green to brown, with reticulated yellow lines that fade with age (2) (4). These lines are the origin of both the common and scientific name of the common map turtle, because of their resemblance to a geographic map (4).

The skin of the common map turtle ranges from olive to dark green or brown-black in colour, and has greenish-yellow stripes (2) (5). The common map turtle is an aquatic species (7), and all four feet are webbed (5). The lower part of a turtle shell is called the plastron (2) (6) and is plain yellow in this species, with a dark seam pattern in juveniles (2) (7).

Common map turtle hatchlings are round in shape with a highly patterned carapace of approximately three centimetres in length (5).

There are no known subspecies of the common map turtle (2).

Also known as
northern map turtle.
Synonyms
Emys lesueurii, Emys megacephala, Testudo geographica.
Size
Male carapace length: up to 16 cm (2)
Female carapace length: up to 27.3 cm (2)
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Common map turtle biology

The common map turtle tends to bask during the middle of the day, and often does so in groups (2) (4) (5) (7). It is very easily startled, and if one member of a basking group is disturbed and moves away, the others will quickly follow (4) (7). This kind of behaviour is observed among most of the turtles of the genus Graptemys (7). Females tend to bask in larger numbers than males and more closely together, sometimes piled on top of one another (2) (4). This is possibly so that they can react more quickly as a group to a perceived threat (2) (4).

The body temperature of the common map turtle is controlled through basking in the summer months and hibernating throughout the winter (4). Common map turtles have been found to uptake oxygen via their skin. This means that they are able to remain in the water for weeks on end and can gain the vital oxygen that they require during hibernation (8).

Annual movements are seen in both male and female common map turtles, possibly to find new nesting and basking sites (4) (7), although summer basking sites are thought to remain the same from year to year (5). These movements are often a series of short distances, less that one kilometre a day, and males move a greater distance, on average, than females (4) (5) (7).

The common map turtle mostly forages for food during the day, in the morning and mid-afternoon (2), and leaves the middle of the day for basking (2). The common map turtle has specialised broad, flat jaws for feeding on molluscs, such as snails and clams, but it is known to feed on insects, crayfish and fish carrion as well (4) (5) (7). Vegetation makes up a small part of its diet (5), and food is always swallowed underwater (4).

Common map turtles mate twice a year, or more, in the spring and in the autumn (2) (5). Average clutches usually contain around 9 to17 eggs (2). The sex of the developing embryos is determined by the incubation temperature (4) (5), as is the case with most species of turtle (6). The emergence of the hatchlings from the nest seems to depend on the nest location, with some emerging in the autumn, and others after winter (2) (9). The nests are generally found in open areas of light soil or sand (2) (5) (7).

Turtle nests in general are predated upon by a range of vertebrates, and this is also the case for the common map turtle (2) (9). Eggs and juveniles have been known to be eaten by racoons, skunks, foxes, otters and rice rats (2) (5). Hatchlings are particularly vulnerable to attacks from birds such as gulls and crows (5). Adult females are at risk of predation when leaving the water to lay their eggs (2) (9), being taken by species such as coyotes (2) (5) (9).

There is very little known about when the common map turtle reaches sexual maturity (2) (5) (9). However, it is thought that females do not mate until they are 19 centimetres in length and around 14 years old (2) (5), while males are thought to mature after 4 to 6 years (5).

The common map turtle is thought to live for up to 20 years in the wild. It does not generally thrive in captivity, but one adult lived to an age of 18 years at Brookfield Zoo, Chicago (9).

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Common map turtle range

The common map turtle is found in the east-central United States and southern Canada. It is found as far north as southern Quebec and northwest Vermont, west through the Great Lakes and south to Alabama (1) (2) (4) (8) (9). The common map turtle has the widest distribution of any species in the Graptemys genus (2).

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Common map turtle habitat

The common map turtle is generally found in large bodies of water, such as rivers and lakes, particularly in the north of its range (1) (2) (4) (9). It is an aquatic species (7), and only leaves the water to bask and lay eggs (4).

This species prefers habitats with abundant basking sites of exposed rocks and fallen trees (2) (4) (5) (7) (9), where it frequently basks together in groups during the summer (4) (7). Larger adult common map turtles tend to be found in deeper water with less vegetation than smaller individuals, and bask farther from the shore (1) (2) (4) (5) (7). Deep, slow-moving bodies of water are used as hibernation sites over the winter months (4) (7).

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Common map turtle status

The common map turtle is classified as Least Concern (LC) on the IUCN Red List (1) and is listed on Appendix III of CITES (3).

IUCN Red List species status – Least Concern

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Common map turtle threats

The common map turtle is still widespread, but its sensitivity to habitat change, as well as its delayed maturity, makes it vulnerable to ongoing development by humans. Common map turtles are habitat specialists, which means that they are unable to adapt if their habitat is altered (4). As such, human impacts on the land through building or farming are not well tolerated, and may cause a reduction in this species’ population size (4) (9). The survival of the common map turtle may also be affected by water pollution that can kill its primary food source of molluscs. In addition, roads near nesting grounds can kill females and young moving to and from the nests (2) (4) (9).

Trade in wild animals also poses a threat to the common map turtle, although this species is difficult to catch because of its extreme wariness (2) (4). Limited historical records mean that it is difficult to assess whether there has been a significant decline in this species (4).

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Common map turtle conservation

The common map turtle is currently listed on Appendix III of the Convention on International Trade in Endangered Species (CITES) (3). This means that the common map turtle is protected in at least one country, which has asked CITES for help in controlling the trade of this species (3).

The common map turtle is protected in most states in its range, and is present in various protected areas (4) (9). Suggestions for the protection of suitable habitats include building platforms for use as basking sites and preventing too many logs being cleared from beaches (4). It has been noted that the accidental introduction of non-native Asian clams might have helped reduce population decline in the common map turtle in some areas by providing it with an alternative food source (5).

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Find out more

Find out more about the common map turtle and other turtle species:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Carapace
The top shell of a turtle or tortoise. In arthropods (insects, crabs etc), the fused head and thorax (the part of the body located near the head), also known as the ‘cephalothorax’.
Carrion
The flesh of a dead animal.
Genus
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Hibernation
A winter survival strategy in which the animal passes the winter in a resting state. This period of inactivity is characterised by specific biological and biochemical changes including lowered blood pressure and respiration rate. In reptiles, this is also known as brumation.
Incubation
The act of incubating eggs; that is, keeping them warm so that development is possible.
Molluscs
A diverse group of invertebrates, mainly marine, that have one or all of the following; a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
Plastron
The lower shell of a turtle or tortoise.
Reticulated
Marked with a criss-cross or network-like pattern.
Sexual dimorphism
When males and females of the same species differ in appearance.
Subspecies
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
Vertebrates
Animals with a backbone, including mammals, birds, reptiles, amphibians and fish.
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References

  1. IUCN Red List (September, 2013)
    http://www.iucnredlist.org/
  2. Ernst, C.H. and Lovich, J.E. (2009) Turtles of the United States and Canada. Second Edition. The John Hopkins University Press, Baltimore.
  3. CITES (September, 2013)
    http://www.cites.org/
  4. Roche, B. (2002) COSEWIC Status Report on the Northern Map Turtle Graptemys geographica in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa.
  5. Jensen, J.B., Camp, C.D., Gibbons, W. and Elliott, M.J. (Eds.) (2008) Amphibians and Reptiles of Georgia. University of Georgia Press, Athens, Georgia.
  6. Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.
  7. Trauth, S.E., Robison, H.W. and Plummer, M.V. (2004) The Amphibians and Reptiles of Arkansas. University of Arkansas Press, Fayetteville, Arkansas.
  8. Jackson, D.C. (2011) Life in a Shell: A Physiologist’s View of a Turtle. Harvard University Press, Cambridge, Massachusetts.
  9. CITES Prop. 10.59 - Consideration of Proposals for Amendment of Appendices I and II (September, 2013)
    http://www.cites.org/eng/cop/10/prop/E-CoP10-P-59.pdf
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Common map turtle  
Common map turtle

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