Discover Maryland's Herps

Field Guide to Maryland's Turtles (Order Testudines)

Family Emydidae

Northern Diamond-backed Terrapin
Malaclemys t. terrapin


Photo of Northern Diamond-backed Terrapin courtesy of Lori Erb

Size

Adult females, 6 - 9 inches. Adult males, 4 - 5½ inches.

Appearance

  • The color of the carapace (top shell) is highly variable from gray, brown, greenish, yellowish to black.

  • The carapace is wedge-shaped, the widest part being the rear half.

  • Each scute (scale) has a series of concentric growth rings or ridges, which often differ in pigment from the ground color.

  • Many individuals have a series of small knobs running down the centerline of the carapace, which is known as a “keel”.

  • The skin on the head and limbs is grayish flecked with black “comma-shaped” spotting.

  • The lips are yellow to light pink, often with a black “moustache”.

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    Photo of Northern Diamond-backed Terrapin courtesy of John White
    Photo of Northern Diamond-backed Terrapin courtesy of John White

    Habitats

    A turtle of estuaries and tidal rivers. It can be found on sandy beaches and bay islands where it lays its eggs in late May to early July, coastal marshes, and any brackish waters.

    How to Find

    Look for them along coastal bay shorelines, islands and marshes during the breeding season, where they are easily captured.

    They can be observed in the water through binoculars, with their inquisitive heads extended “periscope” fashion.

    Photo of Habitat for Northern Diamond-backed Terrapin courtesy of Rebecca Chalmers
    Photo of Habitat for Northern Diamond-backed Terrapin courtesy of Rebecca Chalmers

     

    Distribution in Maryland

    East of the Fall Line, southern Maryland (Prince George's, Anne Arundel, Charles, Calvert and St. Mary's Counties) to the Eastern Shore.

    Maryland Distribution Map for Northern Diamond-backed Terrapin

     

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    Maryland Amphibian
    and Reptile Atlas Project

    "A Joint Project of the Natural History Society of Maryland, Inc. and the Maryland Department of Natural Resources"

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    The Maryland Herpetology Field Guide is a cooperative effort of the MD Natural Heritage Program and the MD Biological Stream Survey within the Department of Natural Resources and their partners. We wish to thank all who contributed field records, text, and photographs, as well as support throughout its development.