Northern Map Turtle
Graptemys geographica

Common Name:

Northern Map Turtle

Scientific Name:

Graptemys geographica

Etymology:

Genus:

Graptemys is derived from the Greek word grapho which means "write" and emys which means "freshwater tortoise".

Species:

geographica is from the Greek word geo which means "earth" and grapho which means "write". referring to the reticulated pattern on the carapace.

Average Length:

females 7 - 10.8 in. (18 - 27.3 cm), males 3.5 - 6.3 in. (9 - 15.9 cm)

Virginia Record Length:

9.6 in. (24.4 cm)

Record length:

10.8 in. (27.3 cm)

Virginia Wildlife Action Plan Rating Tier IV - Moderate Conservation Need - The species may be rare in parts of its range, particularly on the periphery. Populations of these species have demonstrated a significant declining trend or one is suspected which, if continued, is likely to qualify this species for a higher tier in the foreseeable future. Long-term planning is necessary to stabilize or increase populations.

PHYSICAL DESCRIPTION: This species is somewhat large-sized freshwater turtle. Carapace is generally smooth with a keel (may be slightly knobby) and a jagged posterior edge and a maximum carapace length of 244 mm (in VA) . It is flattened and brown to olive with fine, yellow markings in a reticulate pattern resembling a chart of canals and waterways. Carapacial scute pattern is 12 marginals on each side, 4 pleurals on each side and 5 vertebrals. Plastron is yellow to cream with no pattern in adults and it has a maximum length of 213 mm (in VA) which is 85-87 % of the carapace length. It is hingeless. Skin is brown to olive and is patterned with thin yellow markings, the most distinct being a longitudinal yellow blotch behind the eyes that varies in size and shape between individuals *10760* *11407*. Juveniles are similar to the adults but the shell is rounder for the first 1-2 years of life. Carapace length of 13 Virginia hatchlings was 30.7-33.4 mm (avg. = 32.1+/-0.8), plastron length was 27.9-37.1 mm (avg. = 28.9+/-0.8) and mass averaged 8.0 grams *10760*.

SEXUAL DIMORPHISM: Females are much larger than males averaging 206.9 +/-33.7 mm CL, 179.0 +/- 27.4 mm PL and 1,052.7+/-408.5 g body mass. Males on the other hand average 96.9 +/- 14.4 mm CL, 82.4 +/- 11.0 mm pl, and 106.7 +/- 42.1 g body mass. The anal opening in males extends past the posterior edge of the shell , and females have a rounder carapace *10760*. Map turtles may be confused with Chrysemys picta, Pseudemys concinna concinna, and Trachemys scripta trootsii, especially from a distance. Chrysemys picta have an unkeeled carapace, and 2 yellow spots instead of one behind the eye. The patch behind T. s. troosti's eyes is large and elongated and each pleural scute has a streak. P. c. concinna has no yellow blotches behind the ears *10760* *11332* *11343*.

REPRODUCTION: Nesting occurs from May to July with mating occurring in late summer and fall. Nesting is done in soft soil or sand usually in full sunlight. The females usually nest before 8 am. A clutch is usually between 10-16 eggs with an average of 12. Eggs hatch in August and September. Females apparently produce up to 2 clutches per year as evidenced by the presence of oviductal eggs and enlarged follicles in three females. Clutch size in Virginia is 13-16 (avg. = 15.0+/-1.7, n = 3). Egg size averaged 35.0+/-1.0 x 21.3+/-0.9 mm (33.2-36.6, 19.5-22.4, n=29) and weighed 8.1-9.8 g (avg. = 9.0, n=2). A single clutch hatched on 4-6 September after a 74 day incubation period in the laboratory. Hatchlings have been known to overwinter *10760,11624*.

BEHAVIOR: This turtle is nocturnal to slightly crepuscular remaining asleep in the sunshine most of the day. They rarely leave the water except during nesting. This species is extremely reluctant to hibernate and has been known to be caught on the beach after the lake freezes over. When they do hibernate they burrow under rocks and ledges in slow, deep water. It is usually active from April to September throughout its range. The species is extremely gregarious sometimes piling 4 deep. The map turtles primary food item is freshwater mollusks but they will also eat aquatic insects, dead fish and some vegetation. Map turtles are wary baskers and will dive off basking sites with little provocation; when one dives in, others will follow. Large turtles will often displace smaller ones at the best basking sites and large ones will bask further away from shore than small ones *10760*.

POPULATION PARAMETERS: Population ecology of this turtle in Virginia is unknown. A study in Wisconsin indicated that the microhabitat the nest is in affects the sex ratio. Low nest temperatures (23-28 degrees C) produce males and high nest temperatures (30-35 degrees C) produce females. Home ranges in a Pennsylvania river was 170-6070 m for males and 0-5290 m for females. Movements along the river were associated with summer foraging and nesting behavior *10760,11624*.

AQUATIC/TERRESTRIAL ASSOCIATIONS: Prefers to use larger water bodies and usually rivers. They prey heavily on freshwater mollusks. The young turtles and eggs are preyed on by otters, raccoons, opossums, wading birds, other turtles, and snakes. The loss of wetland habitat has greatly affected the numbers of this turtle *10760,11407*.

References for Life History

  • 1027 - Carr, A.F., 1952, Handbook of Turtles. Turtles of the United States, Canada, and Baja California, 542 pgs., Comstock Publ. Assoc., Cornell Univ. Press, Ithaca, NY
  • 2988 - Ernst, C.H., R.W. Barbour, 1972, Turtles of the United States, 347 pgs., Univ. Press of Kentucky, Lexington
  • 3067 - Conant, R., 1978, Field guide to reptiles and amphibans of eastern and central North America 2nd.ed., 429 pgs., Houghton Mifflin, Boston
  • 10760 - Mitchell, J. C., 1994, The Reptiles of Virginia, 352 pgs., Smithsonian Institution Press, Washington, DC
  • 11407 - Conant, Roger and, Collins, John T., 1998, Peterson Field Guide: Reptiles and Amphibians, Eastern/Central North America, 616 pgs., Houghton Mifflin Company;, Boston
  • 11624 - Mitchell, J. C., 2001, Personal Communication, Expert review for GAP Analysis Project, Mitchell Ecological Research LLC

Photos:

*Click on a thumbnail for a larger version.


Verified County/City Occurrence

Hampton City
Lee County
Prince William County
Russell County
Scott County
Smyth County
Tazewell County
Washington County
Verified in 8 Counties/Cities.



FROGS

Virginia is home to 28 species of frogs and toads.

SALAMANDERS

We have a large diversity of salamanders consisting of 56 different species and subspecies.

LIZARDS

Virginia is home to 9 native lizard species and two introduced species, the Mediterranean Gecko and the Italian Wall Lizard.

SNAKES

The Commonwealth is home to 34 species and subspecies of snake. Only 3 species are venomous.

TURTLES

Virginia has 25 species and subspecies of turtle. Five of these species are sea turtle.