Diamondback Terrapin
(Malaclemys terrapin)
Tanner Nance & Gabriella de Souza
Introduction
The Diamondback Terrapin is a unique species of turtle found in the eastern portion of North Carolina! What makes this species unique that they are a species of brackish water turtle, accepting a wide range of salinities in the marshes they inhabit. The shell of this species ranges from gray to black, with hints of green, red, or brown. These turtles have been referred to as "wind turtles" as they have swirls along each scute of their shell, adding to their beautiful appearance. The scales of the Diamondback Terrapin range from gray to white in color and are filled with black spots. The appearance of this species has contributed to its desirability in the pet trade.
Taxonomy
As mentioned before common names for this species include the diamondback terrapin and the wind turtle, with the scientific name being Malaclemys terrapin. This species of turtle belongs to the Emydidae family, which includes ~50 other species, all of those being considered pond turtles or terrapins. Out of that 50, all species are found in the western hemisphere, with the exception of the European Pond turtle (Emys orbicularis) and the Sicilian Pond Turtle (Emys trinacris). The Diamondback Terrapin is the only species of turtle in the United States that spends its life hanging out in brackish water marshes and estuaries.
Kingdom: Animalia, Phylum: Chordata, Class: Reptilia, Order: Testudines, Family: Emydidae, Genus: Malaclemys, Species: terrapin
Niche and Habitat
The Diamondback Terrapin is considered a secondary consumer and preys on blue crabs and snails. This species primarily resides in tidal creeks and marshes. This terrapin can tolerate freshwater, but prefers saltwater or brackish water.
They typically lay their eggs in the late spring or early summer (May - June). They lay approximately 10 to 15 light pink eggs in shallow sand nests. These eggs take anywhere from 60 to 100 days to hatch. Diamondback Terrapins are known to live in the wild for up to 25 years, but they encounter many life threatening situations such as predation, boat propellers, and crab pots.
This image shows the population distribution of the Diamondback Terrapin. Image Source: http://herpsofnc.org/diamondback-terrapin/
Evolutionary History
Diamondback Terrapins spend most of their lives inhabiting estuaries and marshes, but why are they the lone brackish water turtle species in the United States? This species has evolved to have both physiological and behavioral traits best suited to fit their niche environment. These traits include the addition of salt glands, found under the turtles eyes, which expel excess salt when the waters get too salty. This is a trait shared with sea turtles! Diamondback Terrapins will also move to areas of ideal salinity, and will refuse to drink water in areas where salt content is too harsh for the salt glands to work efficiently. The payoff these complex adaptations is that this species is able to live in an environment packed with hard bodied invertebrates and tons of young fish.
Environmental Impacts
Diamondback Terrapins are known to regulate the Periwinkle Snail populations in salt marsh habitats. When the terrapins eat the snails, their jaws make very loud popping sounds. Periwinkle Snails feed upon many of the marsh grasses, like Spartina alterniflora. This is an ecological example of top down regulation. The predator, Diamondback Terrapin, regulates the snail population allowing the cordgrass (Spartina alterniflora) population to flourish. Coastal marsh habitats depend on this food web interaction in order to retain shoreline structure via cordgrass root systems.
Conservation
These terrapins live in constant danger of human threats such as crab pots, boat propellers, pollution, and dredging in addition to natural threats like predation. One of the number one causes of Diamondback Terrapin death are crab pots, which can trap the terrapin and cause it to drown. According to the International Union for Conservation of Nature, the Diamondback Terrapin is a near threatened species. This means that scientist believe this species could experience endangerment in the future. The NC Wildlife Resources commission has a ban on hunting Diamondback Terrapins and have listed this species as a "non-game species" and have also listed it as a "species of special concern."
Friends or Foes?
The Diamondback Terrapins live in marsh and brackish water environments and feed on blue crabs, periwinkle snails, fiddler crabs and many invertebrates. As mentioned before, these terrapins play a vital role in marsh ecosystems by maintaining the snail populations. The terrapin eggs that are laid along the shoreline are exposed to predators like racoons and foxes. Predation is the second most common cause of Diamondback Terrapin death.
Studies have revealed that Diamondback Terrapins are hosts for many parasitic flatworms and flukes. These parasites can be found throughout the terrapin's body and feed on the blood and other body fluids of their turtle host.
Videos
Video Source: https://www.youtube.com/watch?v=oVLmIbyxxxs
This short clip features a captive specimen eating what they naturally would in the wild, fiddler crabs! This video gives viewers a close look at how powerful a diamondback terrapin's jaws are and how food motivated they can be!
Video Source: https://www.youtube.com/watch?v=oN0fNYwiGHQ
Biologist from the University of Alabama at Birmingham put together a video about the diamondback terrapin's history in Alabama, efforts they're making to conserve this species in a laboratory setting, and some footage of field work being conducted. This video is less than 15 minutes in length and would be a great resource for learning about conservation efforts being made to protect this species!
Web Resources to Explore
This PDF is a very detailed species profile of the Diamondback Terrapin. Information is listed on the terrapin's habitat, diet, history, and more.
Human Impacts on Salt Marshes: A Global Perspective
This book provides an excellent view of salt marsh food web structure and profiles on the organisms that live there.
Herps of NC - Diamondback Terrapin
This webpage consists of a brief species profile of the Diamondback Terrapin as well as a great photo gallery of the terrapins in their natural habitat.
The Coastal Review wrote a detailed article on the Diamondback Terrapin and uses many photos taken along the North Carolina coast.
NCpedia is a web database for all things related to North Carolina. Here, you can find a page about the Diamondback Terrapin in full detail.
The Gap Data Tool provided by NC State University is an online database of GIS datapoints that illustrate various species distributions.
Other Sources:
5E Lesson Plan - Estuary Adventure
Diamondback Terrapin_Lesson Plan.docx