Wildlife Profile:

DIAMONDBACK TERRAPIN

Courtesy John R. Quinn,
Fields of Sun and Grass

By Kathy Urffer

Diamondback Terrapin populations can be found along the Atlantic and Gulf Coasts of the U.S. Although their range covers thousands of miles, terrapins only inhabit the thin strip of estuaries and coastal marshes right along the coast, so their actual habitat area is quite small. Terrapins are the only species of turtle, of the approximately 270 species in the world that are exclusively adapted to live in brackish water.

Terrapins were once highly prized for their meat. In the mid-1800s, they were harvested in huge numbers to make soup which led to severe declines in many local terrapin populations. By the mid-1930s terrapins had become so rare in the region that they were considered locally extinct.

Terrapin populations have steadily recovered in many areas but are still threatened by intense coastal development. Dredging, filling, and marshland alterations have maimed the environment that is critical to terrapin survival. In our area, lawns and bulkheads now replace many of the areas that were once suitable nesting beaches leaving only the shoulders of heavily trafficked roads adjacent to salt marshes. Consequently, large numbers of females are killed by motor vehicles during their nesting season from May to mid-July.

In May 2001, Hackensack Riverkeeper began working on the Diamondback Terrapin Mortality Reduction Program, which was begun in 1998 by the Edison Wetlands Association (EWA) and the New Jersey Turnpike Authority. Our staff monitors barrier fences at four locations along the Turnpike. The fences discourage terrapins from crossing the busy roadway and instead guide them back to the creeks that flow underneath the highway. The females can then access their nesting grounds in safety.

Terrapins grow slowly, taking 3-8 years to mature and during the incubation and hatchling stages survivorship is very low. Predators, such as raccoons and foxes, destroy many nests. Root predation, another peril, occurs when the roots of beach plants invade a nest, penetrate the eggs, and absorb their nutrients. Once hatched, juveniles tend to avoid open water, and they prefer burrowing under shoreline debris, mud and tidal wracks of cordgrass.

In south Jersey efforts have been made to promote the survival of diamondbacks by the Wetlands Institute in cooperation with Richard Stockton College. The partners operate a "head-starting" facility for baby terrapins from undamaged eggs taken from road-killed females during the nesting season. The juveniles are eventually released back into the salt marshes from which their perished mothers emerged. For information on educational programs at The Wetlands Institute, call 609-368-1211.

While releasing turtles from pet stores and food markets might seem like a humane action, it is illegal and may be dangerous to local populations. Released turtles may introduce new diseases into native populations, with disastrous results. If you have a diamondback terrapin or find one that has been hurt, please call NJ Endangered and Non-game Species Program at 609-292-9400.

If you would like to learn more about terrapins or about opportunities to participate in the on-going research at Jamaica Bay Wildlife Refuge, please contact Dr. Russell Burke, Department of Biology, Hofstra University, Hempstead, NY, 11549, (516) 463-5521.

This article has been adapted from information provided by Dr. Russell Burke and The Wetlands Institute.


Five dinner plate-sized terrapins sun themselves on a mud flat at low tide.

Photos by Bill Sheehan
 
Snow-fencing erected along the side of the Turnpike prevents pregnant terrapins from crossing the busy thoroughfare and instead directs them back to the creek where they can swim underneath the highway to their nesting grounds beyond.

DID YOU KNOW?

1) Terrapins are sexually dimorphic which means that males and females look markedly different from each other. Females are much larger and their shells range from 6 to 9 inches in length. The shells of adult males rarely exceed five inches in length.

2) The amount of variability in colors and markings within populations of the northern diamondback (Malaclemys terrapin terrapin) is far greater than is typically seen in other turtle species. The color of the shell and skin may range from pale yellow or pale green to tan, brown, orange, gray or coal black. Their body may be uniform in color or it may be decorated with a variety of spots, stripes, splotches, or irregularly shaped concentric rings.

3) Terrapins, like many other species of turtles have temperature dependent sex determination. Rather than sex chromosomes, the gender of terrapins is determined by the temperature at which the eggs are incubated. Higher temperatures create females.

4) Terrapins hibernate during the winter. Some bury themselves in the mud along creek banks in the intertidal zone. Others simply sink to the bottom of marsh creeks and become inactive.

5) Terrapins are broad-spectrum carnivores, which puts them at the top of the salt marsh food web. Mature terrapins forage for a variety of small mussels, clams, fiddler crabs, and snails, which they crush in their powerful jaws. Occasionally they will munch on minnows.


In our region research on nesting terrapins has been conducted at Jamaica Bay Wildlife Refuge. Mating occurs in May and June, when aggregations of more than 100 terrapins can sometimes be seen in the offshore channels. In June and July, female terrapins come on shore to nest, most commonly in dunes, grassland, shrubland, beaches, and sand and gravel trails. Females lay 3 to 18 eggs per nest. Some females can lay two nests per year. Eggs take 70 days or more to hatch. Some hatchlings emerge in the late summer and early fall, whereas, other hatchlings overwinter in their nests and emerge the following spring. No one knows how long terrapins may live.

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