Diamondback Terrapin Fact File
Wild 25 years
Captive 25 years
Diamond terrapins are named after the pattern of diamond-shaped rings which are found along the upper shell against the dark colored background. This contrasts with the beautifully patterned grey and back skin on the head.
They are able to survive in areas of brackish water with high salt levels due to the ability to excrete salt from a gland near the eye.
Eggs are laid in the sand but due to predation and flooding only a small percentage of hatchlings will survive to reach adulthood.
Due to hunting to fuel trade for turtle soup these animals were almost driven to extinction in the 19th century. Today they are threatened by disturbance and habitat destruction.
Read on to learn more about these reptiles.
Diamondback terrapins draw their name from a series of diamond-shaped rings which pattern their upper shell. These rings show the growth of the turtle and can be a different color to the shell. This is highly variable in color being brownish, greenish, grayish or even black. The underside of the shell is yellowish or greenish.
The pattern on their scutes (scales) is unique to each turtle similar to the fingerprints of us humans.
Across the rest of their skin they are a pale gray or whitish with a pattern of blacks spots and streaks across this.
At the end of the body is a horny beak which has a black ‘moustache’ above it. This beak is used to crush their food.
Each leg ends with a foot with webbing between it and strong claws to aid with digging. These large webbed feet and strong legs help them to push their way through the strong currents.
Near the eyes is a salt gland which helps to remove excess salt from the body.
Females grow to a significantly larger size than the males. A diamondback terrapin will measure up to 23cm (9in) long with a weight between 230 and 680g(0.5 and 1.5lbs).
Diamondback terrapins are carnivores. They feed on molluscs, clams, fish, worms, insects and crustaceans. Some plant material, algae and carrion may also be consumed.
They are a predator of salt march periwinkle snails and when the turtles are removed from a habitat it leads to an increase in these snails which will damage the habitat.
While they primarily live in saltwater the diamondback terrapin must drink freshwater to survive.
North America is the native home of the diamondback terrapin. Here they can be found in the following states – Louisiana, Delaware, Texas, Mississippi, Georgia, New York, Massachusetts, Florida, North Carolina, New Jersey, South Carolina, Maryland, Alabama, Connecticut, Rhode Island and Virginia.
An established population exists in Bermuda and is currently considered native but may have been the result of a human introduction.
Their range is highly discontinuous along the east coast. It is as yet unclear if this comes from natural boundaries or is a result of human development.
Diamondback terrapins are found in saltmarshes and mangrove swamps. They mostly inhabit brackish waters along the coast such as estuaries, lagoons and tidal creeks.
They are the only US turtle to live exclusively in brackish water.
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Egg-laying takes place around April and May with some variation in this across their range. It usually occurs in the water during the night.
Across their range they have highly variable clutch sizes from 4 up to 26. These eggs are colored pinkish-white and deposited in sand on the beach or among dunes. In some parts of their range they will produce up to 3 clutches each year.
Incubation length is variable from 60 to 85 days.
Gender at hatching is determined by temperature. Lower temperatures produce males and higher temperatures produce males.
Hatchlings leave the nest and move to the water. Unfortunately they may become stuck in vehicle tracks left in the sand and if they cannot escape they may dehydrate and pass away.
As few as 1-2% of hatchlings are thought to reach adulthood due to the wide range of threats they face.
Sexual maturity is reached at 7 years old. In the north they mature later than those in the south. Males tend to mature younger than females.
When not looking for food the diamondback terrapin will bask on an exposed sandbar or marsh bank.
In parts of their range they will spend the cold winter months buried in mud at the bottom of a tidal creek inactive in a state close to hibernation.
Predators and Threats
Eggs are predated by large fish, birds such as crows and waders along with the animals above.
When threatened these reptiles will move quickly in to the water. Here they are more agile and can hide easier.
Humans present a range of threats to the diamondback terrapin. These include capture in fishing gear and vehicle strikes, development removing their nesting sites, increased predator abundance and loss of habitat. Vehicle strikes increase in number around mating season when females are moving around more.
This species was almost driven to extinction during the late 19th century due to their use for food. To combat this farming operations were established. Eventually demand decreased and their numbers began to increase around the 1930s.
The population of diamondback terrapins is decreasing. Currently around 100 are thought to be part of the population in Bermuda.
The diamondback terrapin is the state reptile of Maryland.
Seven subspecies of the diamondback terrapin are recognized.
Terrapin is an Algonquin word which refers to an edible turtle found in brackish water.
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J.D. Willson, CC BY 2.5 <https://creativecommons.org/licenses/by/2.5>, via Wikimedia Commons
Zihao Wang, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
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