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Our diamondback terrapin group is on display May-August each year. All of the animals in the group are rehab animals that were injured and their injuries prevent their release back to the wild.
The northern diamondback terrapin may be a familiar animal to visitors of the beaches in New Jersey but many people are surprised to learn that this species is in danger. Terrapin populations face a number of dangers – they are still hunted for their meat, they drown in commercial and recreational crab traps, salt marsh habitat is drained and developed, and terrapin females are hit by cars as they cross roads to get to nesting grounds. The Philadelphia Zoo helps terrapins by participating in the Terrapin Headstart Program with Stockton State College and the Wetlands Institute in New Jersey. Staff from Stockton and the Wetlands Institute patrol roads that run through terrapin habitat and look for females that have been hit by cars. If the female cannot be saved, staff harvest the eggs and place them in an incubator. Terrapins that hatch out of these eggs are given to the Zoo to raise until they are large enough to survive release back into the wild.
There is some confusion about the definition of the terms turtle, tortoise and terrapin. Turtles, tortoise and terrapins all belong in the taxonomic order of Testudines and grouped together can be referred to as chelonians. However, the definition of turtle, tortoise and terrapin varies depending on what part of the world you live in. In the United States, the name turtle usually refers to species that live in fresh water, tortoise to land dwelling chelonians and terrapins are those species that live in brackish water. This is not 100% consistent though as evidenced by sea turtles and box turtles who live in salt water and on land respectively. Diamondback terrapins are a distinctive looking species and are unique because they are the only chelonian species native to the United States that lives in brackish (mix of salt and fresh) water. They get their name from the raised diamond shaped rings on the top of their shell that are thought to resemble a cut diamond. Their skin is silvery grey in color with varying spots and stripes in black. The shell has varying shades of tan, yellow, black and olive. They have relatively wide variation in appearance with some animals having very contrasting patterns while others are more muted in coloration. The spots and stripes on the skin are unique to each individual.
Like many chelonians, diamondback terrapins are a slow maturing and long lived species. While no one has been able to document the potential lifespan of a terrapin, a number of specimens have reached over 20 years of age. It is possible that this species could live 40 years or more, especially in the zoo environment where animals are protected from typical threats like predation by humans or bycatch in crab traps.
Diamondback terrapins, like all reptiles, are exothermic. This means that they depend on ambient temperatures to maintain their body temperatures. In the winter, terrapins survive by hibernating in the mucky bottom of creeks, estuaries and salt marshes. In the spring, when temperatures begin to climb, the terrapins will emerge. They are not a social species and congregate in the wild only when it is time to breed. In general, males spend almost all the time in the water while females will venture out in order to nest. This means there are a disproportionate number of road deaths of females in this species.
In their northern range, the diamondback terrapin matures slowly. Males reach sexual maturity first between the ages of 5 and 7 years while females aren't ready to reproduce until 8 to 10 years of age. Breeding and nesting occurs in the spring and early summer and females will venture out of the water several times during this period to lay eggs. This is one of the times that terrapins are most at risk because they frequently have to cross busy roadways to get to nesting locations. Once at the nest site, the female will lay 8-12 eggs per clutch and will usually clutch twice per breeding season. The nest sites are frequently located on sand dunes but are subject to predation and disturbance by humans. Eggs hatch after 7-10 weeks and the temperature of the nest determines the gender of the hatchlings. Temperatures between 86-89 degrees Fahrenheit result in female hatchlings while temperatures between 74-82 degrees Fahrenheit produce males.
Female diamondback terrapins have a shell length of 6-9 inches, with several inches more for head and tail while males are significantly smaller with an average shell length of 4-6 inches.
Female terrapins weigh on average 2 pounds while the smaller males ½ pound on average.
Diamondback terrapins are carnivores. In the wild the terrapins consume mostly insects, worms and fish. At the Zoo, turtles are offered a base diet of Turtle Brittle (a commercial diet made specifically for turtles and terrapins). The Turtle Brittle provides the majority of nutrients the animals require. For activity & enrichment their diet also includes insects, worms & small fish. The rescued terrapin hatchlings raised for release are gradually switched to an all whole prey (insect, worm, fish) diet prior to release to ensure the animals readily recognize whole prey as food.
Diamondback terrapins have a large range but occur in a very narrow section of habitat consisting of brackish water marshes. They occur all along the Atlantic coast of the United States from New England to the Florida Keys. The northern subspecies ranges from Massachusetts to Virginia.
On the 2009 IUCN Red List of Threatened Species, the northern diamondback terrapin is listed as Near Threatened.
To learn more about the conservation efforts at the Philadelphia Zoo, click here.
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