Diamondback Terrapin: Ultimate Guide

Whether you’re interested in owning your own diamondback terrapin or maybe you just want to know more about this special species, then keep on reading to find out everything you’ll need to know in our ultimate guide to diamondback terrapins. 

Male vs Female

Terrapins experience sexual dysmorphism which is when two sexes of the same species display different characteristics such as shape, color, or size as a few examples. 

Female diamondback terrapins are much larger than male ones, with females measuring up to 19cm and males only measuring around 24cm across the tops of their shells. 

Male terrapins tend to have a longer and thicker tail than female terrapins with their vents also being located closer to the tips of their tails than females. This is one of the most obvious clues as to whether a terrapin is male or female. 

Female terrapins will have relatively short claws whereas male terrapins will have long claws which they will use to hold onto the female’s shell when mating. 

It is more difficult to identify a male to a female terrapin when they’re not fully matured.


Diamondback terrapins have a unique appearance which makes them more easily identifiable. Their colors and patterns can vary but their most distinguishable traits are the long snake-like neck and their tiny toenails. 

There are 7 subspecies of diamondback terrapins that can have skin colorations of silver to black and shell colors ranging from black, brown, or pale gray.

They’re commonly found in the water but you may find them hanging out on coastal bays, saltwater marshes, or chilling out on the creek banks.

As a Pet

It is legal to own a diamondback terrapin as a pet but as long as they’ve been bred purposefully in captivity to keep as a pet. It is illegal to find a wild species of diamondback terrapin from the wild and keep it as a pet.

They must be bought as an adult as owning a baby terrapin is against conservation law. 

If you want to breed your terrapin you must apply for a special permit from official authorities. 

You’ll need to make sure your tank is big enough for your terrapin to live a happy life. As a general rule, your tank should have 10 gallons of water capacity per inch of your terrapin’s shell. 


The average lifespan of a diamondback terrapin is around 25 to 40 years in the wild which is less than most species of turtles. They have to avoid predators, diseases, and competition for food to live as long as possible.

However, they’re likely to live over 30 years easily in captivity as long as they’re properly looked after and in the optimum environment.


Diamondback terrapins look very much alike and are sometimes confused with their freshwater relatives – turtles. However, they have several adaptations that allow them to adapt to living in the nearshore marine environment. 

Terrapins have salt glands that are used to differentiate between the salinity of drinking waters around them. Unlike their relatives, terrapins will also swim to the surface to drink the freshwater layer that has been left by rain and you may also catch them with their mouths open catching raindrops. 

Diamondback terrapins can also survive in saltwater environments for long periods as their skin is mostly impermeable to salt.

They also have specially adapted ridges in their jaws that help them crush the mollusks that they find in their natural habitats. 

Breeding Season

Terrapins normally mate during the early spring months and will then nest through till the middle of the summer.

However, female terrapins do not need male terrapins to lay eggs. Female terrapins will already have eggs inside of them which a male will then need to fertilize. Without the male, the egg will be laid unfertilized and will not hatch. 

Female terrapins are sexually mature around 3 years old which is when they can begin mating and laying fertilized eggs. 


Females can lay around 2 to 3 clutches of eggs every year, with their clutch sizes ranging anywhere from 4 to 23 eggs. So in one year, a female terrapin could have over 60 eggs in total. 

It’ll take the eggs 60 to 100 days to hatch and female terrapins will need to incubate their eggs in humid vermiculite, otherwise, they’ll keep the eggs inside of them until the temperature gets warmer.  The eggs will not be moved or rotated at any point during the incubation period. 

The warmer the incubation nest is kept the more female terrapins that will develop. If the eggs don’t hatch before the oncoming winter months, then they’ll overwinter and then hatch in the spring. 

Growth Rate

Mature male diamondback terrapins will weigh around 0.5lbs whilst mature female terrapins will weigh 1.5lbs.

The female growth rate is higher than the male growth rate in terrapins because the females are required to put more energy into egg production and development more than once a year so will require a bigger body. This is why females do not fully mature until they are 6-7 years old.

Life Cycle

Adult diamondback terrapins will mate in the early spring and then the clutches of eggs will be laid in the earliest months of summer. These eggs will hatch later in the summer or the fall when the weather is humid. 

It takes 2-3 for a male diamondback terrapin to mature into an adult whereas it takes 6-7 years for a female to mature into an adult, at which point they will be ready to mate. They will then survive for an average of 25 years in the wild. 


There is no current estimate of the diamondback terrapin. There are many conservation programs currently in numerous states that are seeking to improve marine conditions so the population of diamondback terrapins does not decline too rapidly. 

There are 7 subspecies of the diamondback terrapin which you’ll find across many states of the US. 

However, diamondback terrapins are listed as vulnerable species in the IUCN Red List as they are threatened by development and habitat destruction which puts them at a high risk of extinction.


Meat is the primary source of food for diamondback terrapins. When they live in the wild, they’ll eat a variety of aquatic animals such as fish, crustaceans, marine worms, and mollusks, however, they will eat plants if necessary.

Most captive diamond terrapins will be fed a mix of terrapin pellets, snails, shrimp, and any other seafood during a 20-minute session. They will only really eat once a day every other day.

Do not feed your diamondback terrapin anything they wouldn’t find to eat in the wild as this could cause them serious digestive problems. 


The main predators for diamondback terrapins and their eggs are foxes, seagulls, raccoons, skunks, and rats. However, one of the biggest threats to diamondback terrapins are humans and their insistent need to destroy marine habitats for development. 

Roaming Range

Diamondback terrapins tend to always have a home area which they’ll always return to, however, they can roam up to 150 feet a day to find food and to swim around.


When properly looked after in captivity or with access to everything they need in the wild, diamondback terrapins are generally healthy. Although, their biggest health risk is shell diseases and shell fractures, which could then lead to further problems in the body.

Eye Color

Diamondback terrapins have huge black eyes that stare at you when you’re right up close to them.


Diamondback terrapins may hibernate in the winter month as they are cold-blooded reptiles. In the wild, they’ll bury themselves into the mud at the bottom of creeks until they’re completely submerged and stay inactive for the entirety of winter until the temperature becomes warmer.

Can They Swim?

Yes, diamondback terrapins are strong little swimmers due to their webbed hind feet which helps them survive and swim through strong currents. However, whilst they do love swimming they also do like to chill around, so ensuring there is a platform or some plants for them to cling onto in their water tank will allow them to catch their breath. 


You can house your terrapin indoors or outdoors but housing them indoors is easier as you can ensure their climate is humid for them with a heat lamp. You will also need a filter system for your water tank as terrapins are messy eaters.

Make sure there is a dry dock within their tank so they can bask under the light. They should be housed in slightly salty water. 

They will only need to be fed every other day and you should try to maintain their tank every day and do a deep clean every 1 to 2 weeks. 


To buy a diamondback terrapin as a pet could set you back anything from $50 to over $500 depending on their age, sex, size, and where you buy them from.

Setting up your diamondback terrapin tank and getting all the equipment and food you’ll need to take care of them could cost you an initial cost of $200.

You’ll also need to register your diamondback terrapin at a vet which will then cost you an annual fee to stay registered there.

Fun Facts

  • Female diamondback terrapins will mate with multiple males within a short time and then store the sperm and will then produce a clutch of eggs that have numerous fathers
  • The athletics teams at the University of Maryland have used the diamondback terrapin as their official name