Today, diamondback terrapins (Malaclemys terrapin) are fairly common along the east coast United States. They were practically eaten out of existence earlier this century, but fortunately these heavily exploited turtles
have made a good recovery and have re-established themselves over much of their former range.
Few people in Southern California keep diamondback terrapins, but we've been keeping these turtles for eight years. Our first diamondback terrapin, a female, came from our veterinarian and was quickly named Terry by the kids. A mate
for Terry was obtained through a CTTC member, and was probably from a commercial wholesaler. Later, we acquired a
second younger male from New Jersey and a second female that had been raised from a hatchling by another Club member.
Diamondback terrapins show a wide morphological variation. Seven subspecies are recognized that vary in their coloration, markings and behavior as well as their ranges. For instance, there is a Florida form of the diamondback
terrapin which is slate-black in color with a widened head and jaw for eating barnacles off the roots of mangrove
trees. Diamondback terrapins may change in appearance as they get older. For example, our female Terry was very dark
when she was young; now her shell color has lightened up a lot. Because these turtles were collected and transported
to be commercially raised for food in the past, specimens of some subspecies derived from escaped or released captives
may be found outside their expected range and may have influenced the appearance of local populations.
Diamondback terrapins have a wide tolerance of salt in their water, and are the only North American turtles native to brackish (salty, but not as salty as the ocean) waters. They live in salt marshes as far north as Cape Cod, all the
way down to the Florida Keys and around the Gulf Coast from Florida to Texas. Salt concentrations in their wild
habitats have been measured at 28 parts per 1000. Some of their marshes are totally tidal while some are fed by
freshwater springs. Wild hatchlings may spend their first years upstream in creeks. These creeks are sometimes
brackish and sometimes relatively fresh water. As the hatchlings age, they seem to move down to the salt marshes where
nutrients are plentiful and there are good nesting sites. Surfers have found grown terrapins swimming beside them in
the Atlantic Ocean.
Our terrapins are housed indoors in large aquariums with basking areas, filter systems, incandescent lights and
Vitalites. We add salt to their water, 1/4 cup salt to 20 gallons water, and slightly acidify it (to pH 6.8) using
commercial kits available at tropical fish stores. Terry, our egg-laying female, behaves oddly when it's time for her
to lay her eggs. At the appropriate time of year, when she claws and scratches at the glass wall of the aquarium we
place her outside in our box turtle enclosure so she can dig her nest and lay eggs. She lays her first clutch in
January, with up to 3 more clutches laid about a month apart.
In years past, our incubation method was very casual. We would put the eggs on a damp paper towel in a margarine tub and simply leave them in a cupboard over the refrigerator. Last year (1992) was the first year that we used an
incubator for our turtles' eggs. The incubator was a 10-gallon aquarium heated with 15 and 25 watt incandescent light
bulbs to keep the temperature at 80°-83°F (26.6°-28.3°C). The eggs were placed on moistened paper towels in margarine
tubs with tight fitting lids with no holes. A dish of water was placed in the incubator for added humidity. The
containers were checked regularly to ensure that the paper towels remained damp.
Two clutches of five eggs were incubated for about 90 days. Two eggs hatched from the first clutch; all five eggs hatched from the second clutch. Two other clutches were found too late to incubate. While cleaning up in the box turtle yard one day, we were surprised to find a tiny live terrapin among a clutch of dried out eggs! I brought it inside and put it in water. It started to swim right away, and has thrived. We named it Serendipity.
We start the hatchlings on live brine shrimp and then switch them to Tetra Reptomin. The older terrapins eat Purina trout chow and turtle "meat-loaf".
We've had few health problems with the terrapins. Shell rot showed up in a couple of animals obtained through
wholesalers. This was treated fairly aggressively. First, the affected areas were gently scraped with dental tools to
remove all signs of rot. Then concentrated Gentian Violet was painted onto the affected spots. They were kept dry for
few days, then put them back in the water. Their shells healed perfectly. We had two females which were lost when they
became egg-bound. Once a juvenile terrapin had a broken leg, found after an X-ray by the veterinarian. The fracture
probably occurred during a fight with its brother.
Overcrowding can pose a definite problem. Chewed toes and tails can result when turtles are provided with insufficient space. The relative size of cage-mates is a concern as well. We've had situations where we put hatchlings
in with older terrapins, and after about five minutes of not being sure whether the older terrapins were just curious
or being aggressive, we've had to take the hatchlings out for fear that they would be bitten.
Generally, diamondbacks are sweet, gentle but curious turtles. They have a very habitual nature, and learn quickly what times people are normally around. They seem very sociable except when their cage is too small. They enjoy basking
together, often on top of one another, and it isn't always the largest one on the bottom. Our female, Terry, will
threaten to bite her mate when she has had enough of his attentions. They're only aggressive to people when they think
we're something good to eat, and may occasionally mistake fingers for food.
Cape Cod, Massachusetts, is the northern end of the terrapin's range. At Wellfleet Bay, the Audubon Society is
studying the wild diamondback terrapin. They weigh, measure and mark female terrapins captured as they crawl out of
the water to nest in June and early July. There is a tremendous variety of food in the salt marshes and in the spring
the wild terrapins feed well and often. The females are very dense by the time they are ready to lay their eggs.
The Wetlands Institute at Stone Harbor, New Jersey, is head-starting terrapins. In this program, researchers
retrieve eggs from female terrapins killed by road traffic. The researchers incubate and hatch the eggs, and raise the
hatchlings until they are yearlings. The yearling terrapins are then released back into the wild. The yearlings are
much larger and stronger and, hopefully, have a better chance of surviving than hatchlings. Researchers at the
Wetlands Institute have incubated diamondback terrapin eggs at various temperatures. They have found that at 26°C
(78.8°F) the hatchlings are predominately male. At 32°C (89.6°F) the hatchlings are all females, although at this high
temperature some scute abnormalities occur.
Research on terrapins is going on in the Carolinas and elsewhere up and down the East Coast. An unusual method for getting through the coldest part of the year has been found in New Jersey, where terrapins have been found
congregating in sinkholes in mud during February. Terrapins may hibernate in their northerly ranges but do not seem to
hibernate in their warmer southerly ranges.
Although terrapins are recovering from the exploitation of earlier this century, there are several threats to them. Crab nets cause many terrapin deaths by drowning. Seaside development has led to the loss of nesting beaches. Tire
tracks from vehicles used on the sand pose a hazard to hatchlings: they get trapped in the tire tracks and can die
before reaching water. Diamondbacks are protected in several states. Interestingly, in some places the native
beachgrass is now also protected and removal of it is against the law. Researchers have found that the presence of the
beachgrass lowers the temperature of the nesting areas and can affect the sex of the hatchlings.
We would like to part with this suggestion: do not buy terrapins in a pet store. This is a great way to end up with sick animals which will only be of grief to you. Let's kill the demand for pet store turtles and tortoises by not
buying them. Through clubs such as CTTC learn how to take good care of your animals. Get new animals from other club
members that have bred them or kept them for a long time. The result will be healthier and well cared for turtles.
Originally published in the Tortuga Gazette 29(3): 1-3, March 1993