WELLFLEET — A petition submitted to the National Marine Fisheries Service on Sept. 19 by a coalition of 20 nonprofit organizations led by the Tucson, Ariz.-based Center for Biological Diversity seeks to list diamondback terrapins as a federally endangered species under the Endangered Species Act.
The designation could bring benefits to local research and conservation efforts such as those underway at Audubon’s Wellfleet Bay Wildlife Sanctuary as well as challenges when it comes to future harbor dredging.
The listing could also be a long way off. First, the petition will undergo a multistep review by Marine Fisheries. If the agency determines terrapins are a good candidate, the average time between an endangered species petition being filed and a listing being completed is 12 years, according to a 2016 study.
Diamondback terrapins are saltwater turtles that thrive in the salt marshes of Wellfleet and Eastham and are seen periodically in Truro and Provincetown. Their numbers have declined substantially in the last 150 years, and the species is already listed as threatened under Mass. state law. This affords the turtle some protections: killing, harassing, collecting, or otherwise interfering with terrapins is illegal, and projects in terrapin habitat must undergo review before they can go forward.
Because of these existing protections, a federal “endangered” listing might have a less dramatic effect in Massachusetts than it would elsewhere.
Terrapin Troubles
Diamondback terrapins are found in estuaries from Cape Cod to the Florida Keys and along the Gulf of Mexico to south Texas. According to the International Union for Conservation of Nature, which inventories the conservation status and extinction risk of species globally, the terrapin population’s decline is steeper in the southern part of their range. In both coastal South Carolina and the Chesapeake Bay, local populations have declined as much as 75 percent in 20 years.
One of the most severe threats to terrapins is blue crab pots, as the turtles enter them in search of food and then drown when they are unable to escape. This isn’t a major concern in Massachusetts, where there is no commercial blue crab fishery, but recreational blue crabbing is still present here, and the arrival of the invasive European green crab has created a bait fishery for them.
Bob Prescott, director emeritus of the Wellfleet Bay Sanctuary, said that federal listing would likely mean a requirement that “bycatch reduction devices” be used on all crab traps. These plastic panels attach to the opening of crab traps and cost between $2 and $5 each. A Virginia-based study demonstrated that the devices exclude up to 94 percent of terrapins without preventing even the largest crabs from entering.
Barbara Brennessel, who lives in Wellfleet and is professor emerita of biology at Wheaton College and author of a book on terrapin biology, Diamonds in the Marsh, said that the biggest human-caused threats that local terrapins face are habitat loss caused by development, climate change-driven marsh dieback, and being hit by cars.
Local Impact
If terrapins were to be listed as federally endangered, it would shift the burden of overseeing protections to the federal government. It might also make more money available for restoring the population: the U.S. Fish and Wildlife Service’s budget for endangered species conservation is $329 million.
Currently, most research, protection, and habitat restoration work is undertaken by land trusts and organizations like Mass Audubon. “There is a lot of federal funding for restoration, but it doesn’t seem to apply to terrapins,” Prescott said.
Prescott pointed to Brennessel’s work protecting terrapin nests on Indian Neck, where nest mortality from predators is particularly high, as an example of where more money would help. “If she had an extra tech or two in the summer, more time could be spent on protecting nests,” he said.
“Frankly, we don’t know all that much about terrapins in Massachusetts,” said Prescott. Habitat usage in embayments, the importance of uplands where young terrapins grow, and even population size are unknown, he said.
Researchers do have evidence that turtles could be affected by harbor dredging here. Before the federal channel in Wellfleet Harbor was dredged in 2020, researchers attached radio tracking devices to terrapins to determine where they underwent “brumation,” which resembles hibernation. They found that some brumated in the mud that would be dredged and would likely be killed or injured by the dredging.
To mitigate that loss, the town agreed to pay a fee of $30,000 that would be put toward terrapin research and conservation.
According to Will Harlan, the southeast director of the Center for Biological Diversity, if terrapins were federally listed, any future dredging projects “would certainly be possible and would likely continue,” though they would require a habitat conservation plan and would have to demonstrate that they avoided killing or harassing terrapins however possible.
Future fees for dredging projects aimed at mitigating the damage to terrapin populations would likely increase, based on information in the petition. Or they could be offset by another conservation easement project, such as restoring another piece of terrapin habitat.
Prescott said that the current $4.48-million mitigation fee that the Army Corps of Engineers is charging for dredging the Wellfleet Harbor mooring field, a project that has been repeatedly delayed, is not aimed at mitigating harm to terrapins.
Missing Mitigation Funds
A preliminary inquiry by the Independent has found no evidence that the $30,000 mitigation fee for the 2020 federal channel dredging was used for terrapin conservation.
Brennessel and Prescott, two of the most prominent terrapin researchers on Cape Cod, both said they never received any money and do not know what happened to it. “It was supposed to be used for terrapin research and conservation, but I don’t know who has access to that money,” said Prescott, who was on the town’s dredging task force in 2020.
An inquiry with Town Accountant Suzanne Moquin, Assistant Town Accountant Frank Destino, and Town Administrator Tom Guerino resulted in no leads. None of them was employed by the town in 2020.
