Graptemys

Genus of turtles

Graptemys is a genus of freshwater turtles containing 14 species, commonly known as map turtles. Graptemys are small to medium sized turtles that are significantly sexually dimorphic, with females in some species attaining as much as twice the length and ten times the mass as males. Depending on the species, adult males range from 7–16 cm (2.75–6.25 in), adult females 10–29.5 cm (4–11.62 in), and hatchlings 2.5–3.8 cm (1–1.5 in), although some sources indicate female Barbour's map turtles (Graptemys barbouri) grow to 33 cm (13 in) in length. Most species have a distinctive dark pigmented keel that is often notched or serrated running down the center of the carapace and serrated scutes on the rear margin. The head, neck, and limbs exhibit bold patterns of yellow (occasionally orange or red) lines and spots against darker green, olive, or black base colors. The patterns on the head can be important characters in identifying the various species. The common name "map turtle" is derived from the intricate patterns on their shells that are suggestive of topographical maps, although the patterns are more apparent in some species than others, and often become obscure in older specimens. Some species are occasionally called "sawbacks", in reference to the serrated keels on their shell. They are endemic to North America, where most species occur in the rivers of the Gulf Coast of the United States, although three species are more wide ranging, dispersed throughout the eastern two thirds of the greater Mississippi River basin, into the Great Lakes region, and east to New York and southeast Canada. Most Graptemys are lotic (river) turtles, having a preference for moving water and larger lakes, and with long legs, broad feet, and long fully webbed digits they are well adapted for swimming in currents. They primarily feed on fresh water mussels, clams, snails, insects (including larva and eggs), bryozoans, sponges, algae, and various vegetation. Fish only appear in the diets of a few species and then only in a relatively small percentage of the diet. Within this spectrum of food items there is significant niche partitioning among the sexually dimorphic males and females, and microcephalic, mesocephalic, and megacephalic species occurring in the same river drainages. Like all turtles, map turtles are oviparous, typically laying eggs from late June to August. Females lay two to 15 eggs per clutch and depending on a number of variables such as species, size, and age among other factors, may skip a year between clutches, or lay as many four clutches a year. and two species, the yellow blotched map turtle (G. flavimaculata) and the ringed map turtle (G. oculifera) are listed as threatened by the U. S. Federal Government.

The following species and subspecies are recognized as being valid (listed alphabetically by specific name and subspecific name). Nota bene: A binomial authority or trinomial authority in parentheses indicates that the species or subspecies was originally described in a genus other than Graptemys.

The generic name Graptemys is derived from two compounded Greek words, graptos, meaning inscribed or in writing, in reference to the patterns on the turtles shells, and emydos, meaning a freshwater turtle. Three species are named for the rivers in which they were first discovered: Ouachita River (G. ouachitensis); Sabine River (G. sabinensis); Pearl River (G. pearlensis). G. geographica, geographica = geographic map like; G. nigrinoda, niger = black, nodus = knot, node, or knob; G. oculifera, oculus = eye, fero = to bear (eye shape rings on the pleurals scutes); G. pseudogeographica, pseudo = false, geographica = geographic map like; G. pulchra, pulchra = beautiful; G. versa, vers = to change (probably referring to the contrasting head patterns compared to G. pseudogeographica).

Graptemys species superficially resemble many other species of aquatic turtles, including sliders (Trachemys) and cooters (Pseudemys). However, they are distinguished by a keel that runs the length of the center of the carapace. In some southern species, the keel can result in vertebral spines, resulting in the map turtle's other common name — "sawback". They also typically grow to a smaller size at maturity. They are given the common name "map turtle" due to the map like markings on the carapace. Map turtles are known for intricate head markings and strong sexual dimorphism with mature females twice the length and 10 times the mass of mature males.

Females of all map turtle species can be partitioned into three groups based on head (alveolar) width and corresponding ecology and phylogeny. Microcephalic females are narrow headed, sympatric with a broader headed species, and consume few mollusks. Microcephalic species include yellow blotched, black knobbed, ringed, Ouachita, and Sabine map turtles. Mesocephalic females have moderately broad heads and tend to eat mostly mollusks along with softer bodied prey. Mesocephalic species include Cagle's, northern, false, Mississippi, and Texas map turtles. Megacephalic females have exceptionally broad heads, and feed almost exclusively on mollusks. Megacephalic females include Barbour's, Escambia, Pascagoula, Pearl River, and Alabama map turtles. Males do not fit neatly into the three groups describing head width, with differences in head width likely not influencing diet. Due to these differences in head size and jaw strength, females tend to eat much larger prey than the males such as snails, clams, and crayfish whereas the males eat insects and smaller crustaceans. The natural meandering of rivers, riparian forest, and fallen trees and deadwood in the water are all key and vital elements to sustain most map turtle populations, particularly the Gulf Coast species. The outer bend in a river is typically the deeper side, with the stronger current of the main channel, eroding and cutting into the outer bank and falling trees of the riparian zone forest as it does. While the inside of the bend is shallower, with a slower current, dropping silt deposits and building beaches and sandbars. The meandering course maintains a diverse spectrum of water depths, temperatures, currents, soft and hardpan bottoms, as well as fallen trees and logs that get lodged in the bends. Beaches and sand bars are essential nesting sites. The presence of partially submerged deadwood and trees are critical, not only for basking, but for the growth of algae, bryozoans, sponges, snails, insects and their eggs larva that live in the growth, which are important food items for turtles.

Complete and accurate longevity records for map turtles are lacking. A review of zoo records published in 1992 identified the maximum period of time that many species of Graptemys lived in captivity in North American zoos, ranging from eight to 35 years, including: Barbour's map turtle (G. barbouri) 31 years 8 months; false map turtle (G. pseudogeographica ssp.) 32 years and 6 months; Mississippi map turtle (G. pseudogeographica kohnii) 35 years 5 months. However, it is important to note that in every example these records involve turtles that were acquired by the zoos as adults from the wild, or of unknown origins and of undetermined ages. Therefore the records only reflect the period of time that an individual turtle was maintained at the institutions before it died, not the full lifespan of the individual. Subsequently, the longevity of two female Barbour's Map Turtles (G. barbouri) of unknown ages and origin at the Columbus Zoo were reported at 37 and 43 years. Herpetologist Carl Ernst noted northern map turtles (G. geographica) and Alabama map turtles (G. pulchra) likely live well over 20 years in the wild, Based on records of other turtles in the Emydidae family, it is likely Graptemys longevity exceeds these records significantly, perhaps by decades. The state of Louisiana list the ringed map turtle (G. oculifera) as threatened and the Ouachita map turtle (G. ouachitensis) and Sabine Map Turtle (G. sabinensis) as vulnerable. The state of Mississippi list the yellow blotched map turtle (G. flavimaculata) as threatened and the ringed map turtle (G. oculifera) and black knobbed map turtle (G. nigrinoda) as endangered. In Alabama, all six species of map turtles occurring in the state are classified as nongame species protected by the state. In Georgia the Barbour's map turtle (G. barbouri) is as threatened and the northern map turtle (G. geographica) and Alabama map turtle (G. pulchra) are considered rare species ranked S1 and S3 respectively. In Florida Barbour's map turtle (G. barbouri) is state designated as threatened. The Government of Canada list the Northern Map Turtle (G. geographica) is a species of special concern. Seven of the 14 Graptemys species are listed as either, near threatened, vulnerable, or endangered by the IUCN Red List as of 2021

Throughout the pet trade, the Mississippi map turtle, the northern map turtle, and Ouachita map turtle were bred and hatched out by the thousands in the 1970s. Various other turtles were available, but as the salmonellosis Four inch Law was established, map turtles and others slowly decreased in popularity. Today, these same three still hold the title for most common among the pet trade. Other species being captive bred more often include the Texas map turtle, Cagle's map turtle, and the black knobbed map turtle. Some harder to find map turtles include the yellow blotched map turtle and the Pearl River map turtle.