Diamondback Terrapin (Malaclemys terrapin)

Diamondback terrapins (Malaclemys terrapin) have been listed as a globally near threatened species by the International Union for Conservation of Natural Resources (IUCN).  Their status (which varies from state to state) on the east coast of the United States (where this species is endemic) ranges from endangered to a species of special concern.  Massive over-harvesting for food consumption in the late 19th and early 20th centuries lead to huge declines in the North American populations, which continue to be affected by habitat loss, predation, crab trapping activities and commercial harvest for human consumption.

Mature male diamondback terrapin showing a more typical shell colouration and pattern. Note the grey skin with dark freckles; all of Bermuda’s diamondbacks share these same skin characteristics.

Bermuda’s Diamondback Terrapin Project began in 2007 in response to the need to fill an enormous gap in our knowledge of a species that has recently been added to our native fauna list. The origin of diamondback terrapins on Bermuda was tested using a combination of palaeontologic (fossil, radiometric and palaeoenvironmental) and genetic data. These lines of evidence supported the hypothesis that these terrapins are relatively recent (between 3000 and 400 years ago) natural colonizers of Bermuda, most probably having arrived via the Gulf Stream current.  They are quite unique in that they represent the second naturally occurring non-marine reptile that still survives here - the other being the endemic Bermuda skink. Scientist studying their island ecology have provided sufficient information to the Department of Conservation Services that this species was added to the list of species protected under the Bermuda Protected Species Act in late 2011. 

Diamondback terrapin swimming among the prop roots of a red mangrove tree in a brackish water pond. In Bermuda these terrapins are highly dependant on mangrove fringed ponds for their survival. While their former range across the Island is unknown, they are now restricted to only 2 such ponds.

 

Adult female (left) and an adult male (right) diamondback terrapin. This species shows sexual dimorphism (a condition where one sex is clearly physically different than the other). In the case of diamondbacks, females are always much larger in both body size and weight than males.

 

 

Mature male diamondback terrapin clearly showing the concentric rings on each scute of the carapace (top part of the shell) giving the impression of multi-faceted diamonds, hence the name diamondback. Not all terrapins have a uniform set of rings and many have a smooth carapace which occurs with advancing age.

 

 

A diamondback terrapin hatchling. Hatching occurs from July to October and individuals emerge from their nests with an overall shell length of approximately 3 cm, which makes them very vulnerable to predation from yellow-crowned night herons and crows. Individuals keep their colouration and pattern well into adulthood.

 

 

Native Diamondback Terrapin (left) and invasive Red-eared Slider (right). These are the only two species of turtles found in Bermuda's wetlands. The Red-eared Slider can be easily identified by the red stripe behind its eye.

Learn More:   

Bermuda Biodiversity Project Species Profile for the Diamondback Terrapin. 

 

Related Research: