Reptiles

Map Turtle

Graptemys · also called map turtles, sawback turtles

Least Concern ↓ omnivorecarnivore Rivers & wetlands

A map turtle carries the pattern of its name across its own shell, fine pale lines wandering like the contours on a topographic chart. It is a river specialist that piles up on basking logs in groups and plunges away at the first disturbance, and in several species the female grows two or three times the size of the male, with a head broad enough to crush mussels the smaller male could never manage.

Overview

Map turtles are the genus Graptemys, about 14 species of river turtles in eastern and central North America, named for the contour-line pattern etched across the shell. They eat insects, mollusks, and other invertebrates, favouring rivers with sandbars, current, and fallen timber for basking, and are shyer and quicker to flee than pond turtles like the painted turtle.

Two sexes, two diets

Female map turtles of several species grow far larger than males, with a much broader, mussel-crushing head, while smaller narrow-headed males specialise on soft prey like insects — one of the most extreme size splits between the sexes of any turtle, letting each avoid competing with the other.

A genus of single rivers

Many map turtle species are found naturally in only one river drainage, such as the Pascagoula or Pearl systems in the southeastern US — a narrow endemism that leaves them unusually exposed to a single dam or pollution event.

Status

Widespread species like the common map turtle are Least Concern, but several single-river species — the ringed and yellow-blotched map turtles among them — are Vulnerable, Endangered, or Critically Endangered, hit by dams, dredging, and habitat loss on the one river each calls home.

Map Turtle: common questions

Why do male and female map turtles look so different?

The size and head-shape difference is tied directly to diet. In several map turtle species, adult females grow much larger and develop a noticeably broader head with powerful crushing jaw muscles, which lets them tackle hard-shelled prey such as freshwater mussels and large snails that a smaller, narrower-headed male cannot break into. Males, staying small and lightly built, instead specialise on softer food like insects, and this division lets the two sexes exploit different food resources in the same river rather than competing directly with each other for the same prey.

Why is it called a map turtle?

The name comes from the pattern on the shell, where fine, pale, often yellow or orange lines run across the dark carapace in wandering, concentric patterns that resemble the contour lines used on topographic maps to show elevation. The pattern is clearest on younger turtles and can fade or darken with age in some species, but it remains one of the most useful features for identifying a map turtle at a glance, along with the low sawtooth ridge many species carry down the centre of the back.

Are map turtles good pets?

They can be kept by experienced aquatic turtle keepers but are a demanding choice, especially for the larger-growing female of several species, which needs a very large, well-filtered tank or pond with strong water flow to mimic river conditions, plenty of basking space, and UVB lighting. Map turtles are generally shyer and more easily stressed than more commonly kept species like red-eared sliders, and because a number of species are narrowly restricted in the wild and some are threatened, buyers should make sure any turtle is captive-bred rather than wild-caught, and should check local regulations, since some species and localities have legal protections.

Why are some map turtles so endangered when others are common?

The difference comes down to range size. Widespread species such as the common map turtle occupy huge river systems across much of eastern North America, so localised threats in any one place affect only a fraction of the total population. Several other map turtle species, however, evolved in isolation in a single river drainage in the southeastern United States and are found nowhere else on Earth, so a dam, a major pollution event, or sustained habitat degradation in that one river can threaten a very large share, or even the entirety, of the species, which is why narrow-range map turtles are disproportionately represented among threatened turtles.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 11, 2026. Last updated September 11, 2026.

Quick facts

Scientific name: Graptemys
Diet: An omnivore that eats aquatic insects, crayfish, snails and mussels, small fish, and carrion, along with algae and aquatic plants, with the diet split sharply by sex in many species, since large-headed females crush hard-shelled molluscs that narrow-headed males cannot manage, leaving males to specialise on insects and other soft prey
A shell like a map: The carapace is marked with fine, pale, concentric or wandering lines that resemble the contour lines of a topographic map, giving the group its common name, and many species also have a low, saw-toothed keel running down the centre of the back, earning some the alternative name sawback turtle
Extreme size difference between the sexes: Female map turtles grow dramatically larger than males, in some species two to three times the male's length and many times the weight, along with a proportionally much wider head and stronger jaw, one of the most pronounced examples of sexual size dimorphism in any turtle
A river specialist: Map turtles are strongly tied to rivers and large streams with a good current, sandbars, and abundant basking logs, basking in large groups that slip into the water at the first sign of disturbance, and they are generally shyer and harder to approach than pond-dwelling turtles such as painted turtles
Many species from single river systems: The genus Graptemys contains around 14 species, and several are found naturally in only one river drainage each, such as the Pascagoula, Pearl, or Escambia systems in the southeastern United States, a pattern of narrow endemism that makes the group unusually vulnerable to local habitat change
Basking in numbers: Map turtles are highly social baskers, often piling several individuals deep on a single favoured log, and a startled group will plunge into the water almost simultaneously with an audible series of splashes, a behaviour that makes them easy to detect from a distance but hard to observe closely
Hatchlings that may overwinter in the nest: In parts of their range, map turtle hatchlings emerge from the egg in autumn but remain in the underground nest through the winter rather than digging out immediately, surviving cold temperatures before emerging the following spring when conditions improve
Range: Rivers and large streams of eastern and central North America, from the Great Lakes and the upper Mississippi basin south through the Gulf coastal plain, with individual species often restricted to a single river drainage in the southeastern United States, generally favouring large, flowing water with sandbars, snags, and fallen timber for basking.
Conservation status: Least Concern ↓ ≈ Map turtles as a genus show a wide range of conservation status. Some widespread species, such as the common map turtle and the false map turtle, remain numerous across large river systems and are assessed as Least Concern, while several species confined to a single river drainage are Vulnerable, Endangered, or Critically Endangered, including the ringed map turtle of the Pearl River and the yellow-blotched map turtle of the Pascagoula system. The main threats to the more restricted species are dam construction and water level management that destroys basking and nesting sandbars, dredging, pollution, boat strikes on basking turtles, and collection for the pet trade, and because so many species exist in only one river, a single dam or pollution event can threaten a large share of a species' entire population in the wild