Diamondback Terrapins Endangered in Lower Hudson River
A diamondback terrapin seen crawling along the ground. Source: Kat Brask Unspash.
Treading brackish waters with muscular legs and a stout pink nose are the diamondback terrapins. While their greatest threat to their survival used to be commercial harvesting and pollution, now it’s habitat loss and drowning in crab pots, a wire mesh cage used to catch crabs.
Exclusive to coastal salt marshes, lagoons and bays in North America, these turtles can be identified by their speckled, gray to dark colored skin and unique shell pattern. The diamond-shaped scutes, hard plates that make up their shell, are what compose their one-of-a-kind carapace, protective shell covering.
Their ability to survive in these saltier environments comes from their specialized glands that allow them to eliminate excess salt from their bodies. Like sea turtles in this way, they maintain osmotic homeostasis by these glands that keep their body concentrations at balance.
When spotted, an adult female diamondback terrapin can be as large as 12 inches in length while an adult male may be half that. The female has a wider jaw and larger head than her mate, but the male will have a longer tail. A female can lay about 25 to 40 eggs per year after mating in early spring.
Their turtle duties to reproduce new offspring remain incomplete because of their susceptibility to predators. The newly laid eggs in the summer are often prone to predation from racoons, foxes, skunks, gulls and herons that reduce the survival rate of the eggs.
After a long day of swimming in a salt marsh, they may snack on crabs, shrimps and/or mollusks to fill their stomachs and nurture their body. Indirectly, as they eat periwinkle snails, often spotted in the lower Hudson valley, they can keep marshes healthy and limit the snail population.
One of the many reasons the hunting season for diamondback terrapins in New York State was closed in May of 2018 was because of their vital importance and decline in population. This endangered species has an act of aiding health in its natural habitat.
"Diamondback terrapins depend upon a steady diet of mollusks and crustaceans, making them an excellent indicator for the health of New York's estuarine habitats," DEC Commissioner Basil Seggos said in a press release. "If diamondback terrapins are doing well in a bay, you know you have a healthy population of blue mussels, clams, and blue crabs, too."
Since one of the primary foods in the diet of a diamondback is crabs, many of them are near their food but are often caught in crab pots that induce harm. Diamondbacks can’t breathe underwater, and the cage inhibits these turtles from catching a breath of oxygen above water.
“The crabs, of course, have gills, so they can breathe underwater,” Joseph Butler, Professor of biology at the University of North Florida, told WJCT News. “The turtle has lungs. So, it’s just gonna drown eventually.”
Butler and George Heinrich, Executive Director of the Florida Turtle Conservation Trust, developed a bycatch reduction device back in 2007 that saves terrapins from getting caught in the crab pots that they published in Estuaries and Coasts.
Their research showed that a little over 70% of terrapins can be saved using their bycatch reduction devices, BRDs. These BRDs are generally in the shape of a rectangle made of plastic or metal placed at the entrance of the cages.
Under the Magnuson-Stevens Act, fisheries are required to reduce bycatch—catching undesired organisms in gear—to reduce mortality of unwanted creatures and promote the conservation and management of U.S. federal waters.
However, these coastal wetland reptiles remain threatened even with enforced regulations today; 15 years later.
“It is our hope that all 16 states within the range of the terrapin will eventually require the use of BRDs on all crab pots,” Butler and Heinrich said in their 2007 paper.