Determining Gender

Diamondback terrapins are a little harder to determine their gender than most North American turtles. The males do not have long fingernails like many other species of turtles. They have to be at least 4 inches before they can be positively sexed. Often time people will believe they have a female at 3.75-inch only to find out it was a male a few months later. The best way to determine the gender of a 4 inch diamondback terrapin is to look at their tail. Males have much longer and wider tails than females and the vent on a male’s tail is normally an inch below the bottom of his plastron. Once they reach 5 inches it is very easy to tell the two sexes apart. Females carapaces start to develop a higher dome while males have a much flatter carapace. Females also develop wider and larger head at they grow and males heads remain thin and streamlined. Finally when a males tail is fully developed it will be over three times the size of a female.


Males mature faster than females. Males will normally start trying to mate at only 4.5 inches but they are not normally effective until they are 5 inches. In captivity it normally takes males around 2 to 3 years to reach 5 inches and become sexually mature.

Females on the other hand typically take 4 to 8 years to reach maturity in captivity.  Females normally do not start becoming gravid until they are around 6.5 inches. Most females have a very low fertility rate for the first couple of year. It is very common during their first year being gravid for them to drop them in the water or lay a nest with no fertile eggs.

When they are fully grown a male can reach up to 6 inches and a female as large as 10 inches. Though most captive born females stay around 8 inches.


Males instigate the mating process, they will follow a female around and when she stops moving he will start rubbing his tail on her tail. If she does not swim away he will float to a 90-degree angle and his penis will come out of his tail. The male diamondback terrapins penis looks like a jet-black flower; the flower tip is normally twice the width of his tail. The flower part latches on to the females tail and a small spike in the middle of the flower goes into the females tail vent. Once the male is completely attached to the female, he will fall backwards and lay on his back facing away from the female. The mating process can take over 15 minutes. When they are finished the male detaches from the female and retracts his penis back into his tail.

While a lot of mating happens in the spring they can be seen mating throughout the year. There are even sightings of them mating in the dead of winter when the water temperature is in the 50s.


The first part of nesting process is finding a location. A female will walk around for a while and if she finds a spot that she likes she will start digging with her front claws and rubbing her nose in the sand. It is believed that they use their nose to detect if the soil or sand has enough moisture for the eggs’ needs. After a couple of minutes, if she likes the location the female will move forward and start digging with her back feet. With very soft soil it can take them as little as 15 minutes to dig the hole with their back feet. Once the hole is completed they go into a trance like state as the eggs start coming out. They lay one egg at a time and will catch each egg with one of their rear feet and position the egg in the nest before the next egg drops. 

They normally lay between 6 and 12 eggs. The Northern subspecies typically lay more eggs, sometimes as many as 15 eggs. When she has laid all of her eggs she will hold the ground firmly with her front claws and start gathering sand with her rear claws.  Once she has filled most of the hole, she will start reaching further out with her rear legs and grab any leaves or other derby in the area to camouflage her nest. They are so good at this process that it is often impossible to tell that the ground was ever disturbed. The last step in the nesting process is what some call the “knuckle dance”.  This is when they make a fist out of their rear claw and waddle back and forth, packing down the area.

Females can dig many test holes before deciding on a place to nest, this is all part of the nesting process. They will sometimes dig complete nests and then abandon them for no obvious reason. What is really odd is that they will dig test holes even after they have nested their eggs. They can even go through the entire labor process including catching invisible eggs and covering up the hole.  

A female will usually lay more than one clutch a year. After she lays her first clutch of the season they typically nest again in 2 to 3 weeks. This can continue a couple more times. In the right conditions they can lay as many as 5 clutches in one season. Most of the time the number of eggs does not decrease between clutches, in fact they commonly increase.

Digging Up Eggs

Once a female has nested it is important to dig the eggs up as soon as possible. Chances are if she liked the spot where she laid the eggs another female many feel the same way. Failing to remove clutches quickly can cause the nest to be destroyed by another female nesting right on top of a clutch of eggs.  

Carefully remove the sand from around the eggs and then remove the eggs from the nest. Place them into a container with a substrate. Bury the eggs only halfway in the substrate. NEVER tilt or turn the egg from the original position that it was laid in, otherwise embryo might not survive.

There is a chance that eggs dropped in the water might hatch. Incubate them in the same manner as eggs nested normally.

Egg Containers

Glad or Rubbermaid food containers are commonly used. Drill one small hole in the middle of the lid. Fill the plastic containers halfway with substrate. Hatchrite is a great option that is ready to be used out of the bag. Hatchrite is a type of perlite but it comes pre-moistened and free of chemicals.

Perlite can be used as well as long as it is chemical free. A lot of the perlite available at the large hardware stores contains Miracle Grow. If a chemical free perlite is available it will be sold dry. To moisten the perlite as equal parts perlite and water by weight.

Bury the eggs only halfway in the substrate and close the lid firmly. There should be no need to add water to the container during the incubation process.

Temperature Sexing

First attempts at temperature sexing can be a little tricky and it is not always 100% accurate. With practice it can become rather reliable. The most important factor is having accurate thermometers. Also having more than one thermometer in the incubator can aid in receiving the most actuate temperature reading possible.

Incubating diamondback terrapin eggs over 83F should produce mostly female hatchlings. The higher the temperature the higher the chance that they will be females.  Unfortunately higher temperatures also cause scute deformities and other deformities.  About 25% of the eggs incubated for female will also have extra scutes.

Incubating diamondback terrapin eggs at or under 79F will produce nearly 100% male hatchlings.

The cooler the temperature the longer an egg will take to hatch. Diamondback terrapin eggs normally take about sixty days to hatch when they are incubated at around 83F. at 79F the eggs will take about 75 days to hatch.


There are several options to consider when getting an incubator. The first is the size of incubator needed and where it can be stored at. It is best to keep the incubator in a cool location, some where that doesn’t get over 79F is ideal. A lot of incubators will require minor adjustments to make them work for turtle eggs.

Hova-Bators Incubators

Hova-Bator incubators have been used in the turtle hobby for a very long time. I used them for several seasons in the late 90’s and early 2000’s. Hova-Bators can be purchased at most feed stores or online. Make sure it is not the type that rotates the eggs! Use plastic containers to hold the each of the clutches and poke a small hole in the top of the lids. 

Large Cooler Incubator

Another method of incubating is the do it yourself cooler incubator. Use a very large cooler that with heavy insulation (for example 55 gallon Igloo 40 L X 18 W X 20 D). Fill the bottom with four inches with water and made a shelf out of egg-crates. The shelf should keep the eggs at least one inch above the water level. Put a 50-watt submergible heater in the water and set the temperature for the desired gender. Inside the cooler add a couple of mercury thermometers and a digital thermometer that monitors the coolers temperature from outside.     

The main issue with this type of incubator is the humidity level stays very high inside the cooler, nearly 100%.  Perlite in this situation is a great substrate, because of it’s aeration and drainage properties. 

Large Incubator

For a large egg number of turtle egg converting a small refrigerator into an incubator is an excellent idea. Refrigerators work better than wine chillers as they have more insulation.

For the heating element use Flexwatt 11 inch wide heat tape. Run a strip of Flexwatt down the rear of the refrigerator and freezer compartment.  Attached the heat tape to  the housing with Aluminum Foil Duct Tape, typically used for home air conditioning vent system. Use cramping metal connectors to connect Flexwatt to an electrical cord. Flexwatt heat tape supplies are available from BeanFarm.

To improve airflow replace the shelving through out the refrigerator with egg-create.  Added two 4 inch computer CPU 12VDC fan in the refrigerator compartment to also aid with greater air circulation. 

The drawers in the bottom of the refrigerator can filled with a couple of inches of water to provide humidity. In the freezer added a tray with water for humidity.

Each compartment has needs it’s own Helix temperature regulator. The temperature should remain extremely stable.

Hatching Process

In the wild hatchlings need to dig their way out of the nest. This process can take them several days. Depending on the time of year they can even stay under ground in the nest and not emerge until the spring. In captivity they basically just need to get out of the eggs and they are free from their nest. Because of this they have large yoke sacks when they hatch. Leave them in their egg container until their yoke sack is completely gone, this can take up to 2 weeks. Once their yoke sack is gone they can go right into a 10 gallon tank.


The start of hibernation will vary based on location. For setups outdoors, basement or garage as the temperature start dropping in the Fall feed them every three days instead of every other day. Switch the lighting cycle from 13 hours a day to 5 hours a day. Replace the 100-watt basking bulbs with LED bulbs. By the first of November feed them once a week and towards the end of November stop feeding them all togethers. This could be even earlier in the year for colder locations.

Hibernation is not immediate and will take time. They will become less active as the weeks go on. Depending on the water temperature it can take them well over a month to go into hibernation. 55F is a good water temperature for them to hibernate in. The Northern subspecies can handle lower water temperatures.

When the weather starts warming in the Spring set the light cycle back to 8 hours a day. They come out of hibernation much faster than they go into it. Within a few weeks they will be eating every day.

If they are housed indoors they will likely not every hibernate.