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Critterguy / Critter Field Guide / Turtles
Critter Field Guide: Turtles of Michigan

Identification Key

To identify a turtle in hand, close by, or in a photograph, use this quick key.
Each numbered stop below has two statements; pick the one (A or B) that best applies to the turtle in hand. This will lead you either to an identification, or directions to go to another numbered stop. Keep going until you have a proper name for the turtle you are identifying. Click on the name of the turtle to see a photo and detailed description, this should help confirm the identification.


Here are some words which will help you use the key:
Click on the words for an audible pronunciation. (Links open a new window.)
carapace
a turtle's top shell

plastron
a turtle's bottom shell

keel
a raised ridge along the middle (front to back) of the carapace of some turtles

scute
the large, separate scales on the carapace and plastron of most turtles

hinge
a flexible, straight dividing line between two parts (scute pairs) of the plastron of some turtles that allows one of both sections of the plastron to lift up, protecting the head and feet.

The following steps will help you to identify your turtle:
  1. SHELL SHAPE

    1. carapace and plastron very smooth, without separate scutes; shell soft and rubbery at the edges, nose of turtle extended into pig-like snout...
      You have a spiny softshell turtle (watch out—they can bite!!).


    2. carapace and plastron hard or stiff, and divided into separate scutes...
      Continue to Step 2 and look at the TAIL.

  2. TAIL

    1. tail very long, with large scales sticking up along the midline; also note: scales on back edge of carapace form sharp, tooth-like points; plastron very small; mouth has a pointed beak...
      You have a snapping turtle (watch out—they can bite!!).


    2. tail does not have large, thick scales sticking up along the top...
      Continue to Step 3 and look at the BOTTOM SHELL.


  3. BOTTOM SHELL

    1. turtle has skin showing between some plastron scutes; plastron rather small; also note: tail short; snout rather pointed; turtle less than 5 inches long; carapace high and narrow; turtle may open mouth and give off a bad smell when handled...
      You have a common musk turtle.


    2. turtle does not have skin showing between the plastron scutes...
      Continue to Step 4 and look at the COLOR PATTERN.


  4. COLOR PATTERN

    1. turtle has thin yellow or red stripes on its head, neck, and legs...
      Continue to Step 5 and look for RED MARKINGS.


    2. turtle does not have pattern of thin stripes on head, neck, and legs...
      Continue to Step 7 and look for a HINGE.


  5. RED MARKINGS

    1. red markings along the edge of the carapace (on top or underneath, or both); often red striping on neck and front legs; also note: plastron yellow or reddish with dark central blotch or pattern; carapace smooth and without a keel...
      You have a painted turtle.


    2. no red markings on top or bottom edge of carapace and no red striping on legs or neck; carapace faintly to strongly keeled...
      Continue to Step 6 and look at the HEAD & LEG STRIPES.


  6. HEAD & LEG STRIPES

    1. legs, head, and neck with thin yellowish stripes; no red markings on head or legs; also note: carapace has a low to moderate keel and a faint circular pattern of light lines; plastron plain yellow, without dark blotches in centers of scutes...
      You have a common map turtle.


    2. red or orange stripe behind each eye, otherwise only yellow stripes on head and legs; note: old males may become very dark, with shell and skin colors obscured; also note: plastron yellow with a dark blotch in each scute; carapace usually with a very low keel and light streaks on greenish or brown background color...
      You have a red-eared slider.


  7. HINGE

    1. plastron with flexible hinge line between third and fourth pair of plastral scutes (counting from head end); carapace rather high and domed, or "helmet-like"...
      Continue to Step 8 and look for UPPER JAW.


    2. no flexible hinge or plastron...
      Continue to Step 9 and look for a TOP SHELL.


  8. UPPER JAW

    1. upper jaw hooked (like a hawk); also note: head and neck variably spotted or streaked, but throat NOT plain yellow; tail very short; carapace helmet-like...
      You have an eastern box turtle.
      Note: A protected "species of special concern" in Michigan.


    2. upper jaw notched (giving the turtle a built-in "smile!"); chin and throat plain yellow; also note: carapace elongated and dome-like; plastron usually yellow with a dark blotch at the outer edge of each scute...
      You have a Blanding's turtle.
      Note: A protected "species of special concern" in Michigan.


  9. TOP SHELL

    1. carapace smooth and black with few or many round yellow spots; head black with bright yellow or orange spots and blotches...
      You have a spotted turtle.
      Note: A protected "threatened specie" in Michigan.


    2. carapace brownish or grayish-brown (sometimes, with yellow ray-like markings), with deep circular growth rings crossed by ray-like ridges on each scute; also note: head black, with yellow or orange skin on lower neck and under legs and tail...
      You have a wood turtle.
      Note: A protected "species of special concern" in Michigan.


  10. START OVER

List of Turtles in Michigan
    Blanding's turtle (Emydoidea blandingii)
    Description: Blanding's turtle is a medium-sized turtle with an elongated, dome-like carapace and a long neck. The smooth carapace is usually black with a variable number of yellowish spots and streaks. The head is also dark, with brown or yellow spots, but the chin and the underside of the neck are bright yellow. The yellowish plastron has a dark blotch at the outer edge of each scute, and there is usually a flexible hinge between the pectoral and abdominal scutes. A frightened turtle may use this hinge to lift the front and back of the plastron and close up its shell. Hinge flexibility varies greatly among individuals, with some specimens having little or no shell closing ability.
    Adult Carapace Length: 6 to 10.5 inches (15.2 to 26.8 cm).

    common map turtle (Graptemys geographica)
    Description: The map turtle has a greenish, olive, or brown carapace with a low keel and an irregular pattern of yellowish lines that suggest roadways on a map. This pattern may be obscured in older specimens. The skin on the head, neck, and legs is olive or brown with thin yellow stripes, and there is usually a small yellow spot behind each eye. The plastron is light yellow, though young specimens often have dark lines running along the scute edges. Females are bigger and have much wider heads than males.
    Adult Male Carapace Length: 4 to 6.3 inches (10 to 16 cm).
    Adult Female Carapace Length: 6.7 to 10.7 inches (17 to 27.2 cm).

    common musk turtle (Sternotherus odoratus)
    Description: This is a very small turtle with a narrow, high-arched brown or black carapace and a pointed, protruding snout. They usually have two yellowish stripes on each side of the head. (In older specimens these stripes may fade.) Two or more soft, pointed barbels are usually visible on the chin or throat. The yellow or brownish plastron is very small, with many of the scutes separated by skin. The male musk turtle differs from the female in having broader areas of skin between the plastral scutes and a longer, thicker tail tipped with a stiff spine.
    Adult Carapace Length: 3.25 to 5.37 inches (8 to 13.7 cm).

    eastern box turtle (Terrapene carolina carolina)
    Description: This is a small land turtle with a domed, helmet-shaped carapace and a hinged plastron. Coloration of the shell and skin is extremely variable. The carapace is usually brown with a radiating pattern of yellow or orange markings in each scute. The plastron can be yellowish, tan, brown, or black, and either plain or marked with lines or blotches. Skin of the head and legs is usually brown or black with streaks and spots of yellow, but some (especially males) may have the yellow or orange color covering most of the head and forelimbs. The plastral hinge allows the box turtle to close the shell tightly, completely hiding the head, legs, and tail. Most male box turtles have red eyes, while most females have brown eyes.
    Adult Carapace Length: 4.5 to 7.8 inches (11.5 to 19.8 cm).

    painted turtle (Chrysemys picta)
    Description: This is a common, small, dark-shelled turtle with a yellow-striped head and red and yellow stripes on the neck, legs, and tail. The smooth black or olive carapace has red markings along the edge, especially underneath the marginal scutes. The plastron is usually yellow, sometimes tinged with red, with a long, dark central blotch. In some specimens this blotch is nearly absent, while in the western subspecies (see "Distribution and Status") the blotch is wider and more complicated and extends along the seams between the scutes. Males are smaller and have longer front claws than females.
    Adult Carapace Length: 4 to 7 inches (10 to 18 cm).

    red-eared slider (Trachemys scripta elegans)
    Description: The red-eared slider is named for the broad red or orange stripe behind the eye, which may extend onto the neck. Otherwise, the head, neck, and legs are greenish with yellow stripes. The olive or brown carapace usually has yellow and black longitudinal bands and stripes. The plastron is yellow with a dark, rounded blotch in each scute. Males are slightly smaller than females and have longer claws on the forefeet. Old specimens, especially males, may become very dark, with black coloration obscuring the striped pattern on the skin and shell.
    Adult Carapace Length: 5 to 11 inches (12.5 to 27.9 cm).

    snapping turtle (Chelydra serpentina)
    Description: This large aquatic turtle has a big head with a pointed nose and hooked upper jaw, and a long, thick tail with a row of thick scales along the top. The carapace is black, brown, or olive, with pointed marginal scutes along the rear edge. (The shell is often covered with algae or mud.) Young snappers have three lengthwise keels on the carapace, but large adults may have shells that are nearly smooth. The yellowish plastron is small and cross-shaped and leaves much of the turtle's underside uncovered. This lack of protection may partly explain the snapping turtle's well-known biting defense. This is Michigan's largest turtle, often reaching 10 to 35 pounds (4.5 to 16 kg); the record weight was 86 pounds (39 kg) for a captive specimen.
    Adult Carapace Length: 8 to 18.5 inches (20 to 47 cm).

    spiny softshell turtle (Apalone spinifera)
    Description: This medium to large turtle is unmistakable, with its flat, smooth shell and long pig-like nose. The rounded tan, brown, or olive carapace is marked with black dots or circles in juveniles and males, and dark blotches in adult females. The plastron is white, with gray patches over the plastral bones. Both carapace and plastron lack scutes and are quite soft and flexible. The name "spiny" comes from the small spines at the front of the carapace. The neck is very long, and a yellowish, black-bordered stripe is usually visible on the sides of the head. Females are larger and darker and have shorter tails than males.
    Adult Male Carapace Length: 5 to 9 inches ( 12.7 to 23 cm).
    Adult Female Carapace Length: 7 to 19 inches (18 to 48 cm).

    spotted turtle (Clemmys guttata) Threatened
    Description: The little spotted turtle has a smooth, black carapace with a variable number of rounded yellow spots. The plastron is yellow or orange with a black blotch in each scute; the blotches may cover most of the plastron in some specimens. The head, neck, and legs are black above, usually with a few scattered yellow spots, and there are usually one or more irregular orange or yellow bands on the side of the head. The skin under the legs and neck is orange or pinkish. Occasional specimens have no spots on the carapace; others may have only one spot per scute. Males usually have brown eyes and brown or black lower jaws, while most females have orange eyes and yellow or orange lower jaws.
    Adult Carapace Length: 3.5 to 5 inches (9 to 12.7 cm).

    wood turtle (Glyptemys insculpta)
    Description: The scientific name of this species means "sculptured turtle", and its rough, brownish carapace does look as if it was carved from wood. Each scute has deep, circular growth rings crossed by ray-like ridges. The plastron is yellow with a black blotch at the outer edge of each scute and has a V-shaped notch at the base of the tail. The head and upper legs are mostly black or dark brown (rarely speckled with yellow or white), while the neck, lower legs, and other soft parts are yellow or orange. Mature males have higher shells and longer, thicker tails than females.
    Adult Carapace Length: 6.3 to 9.4 inches (16 to 24 cm).


Recommended Books

Michigan Turtles and Lizards by J. H. Harding and J. A. Holman. 1990. Michigan State University Cooperative Extension Service, East Lansing, Bulletin E-2234.

Amphibians and Reptiles of the Great Lakes Region by J.H. Harding. 1997. University of Michigan Press, Ann Arbor.

A Field Guide to Reptiles and Amphibians of Eastern and Central North America by R. Conant and J.T. Collins. 3rd Ed. (1998, 1991) Houghton-Mifflin, Boston.


Acknowledgement

James Harding
MSU Museum
Michigan State University
East Lansing, MI 48824
(517) 353-7978
hardingj@msu.edu

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