A half-dozen leatherback turtles have been found dead along the Massachusetts coast since mid-September, including three found off Cape Cod Bay in the last two weeks, as this largest turtle species expands its territory northward among warming waters, a researcher said.
In past years, the leatherbacks would have come and gone in August, but “everything seems to be later and later now” as oceans and the atmosphere warm, said Robert Prescott, executive director emeritus and director of the sea turtle program at the Massachusetts Audubon Society’s Wellfleet Bay Wildlife Sanctuary.
“September is the new August,” Prescott quipped. “Water temperatures are staying warmer later, and the jellyfish bloom that the leatherbacks feed on is happening in September.”
The finding of the turtles was first reported in the Cape Cod Times.
Some of the turtles appeared to have become tangled in fishing lines or other materials, but others were too decomposed for scientists to say what may have caused their deaths.
The giant creatures range in weight from 600 to 1,500 pounds, according to the World Wildlife Fund. The International Union for Conservation of Nature officially classifies leatherbacks as a “vulnerable” species, but many subgroups of the turtles are listed as “critically endangered.”
The dead leatherback found most recently was at Sesuit Harbor in Dennis on Monday. One was found Sept. 29 on Breakwater Beach in Brewster, and another on Sept. 27 at Bayview Beach in Dennis. Two earlier leatherbacks were found on Horseneck Beach in Westport and along the Marion coastline, Prescott said.
Last year, a living leatherback washed up in Eastham as late as Nov. 11, but it later died, recalled Prescott, who coordinated the turtle’s rescue.
“To have one in November, alive, is pretty amazing,” he said.
He said that, as more and more data become available, it looks increasingly like the expansion of the turtles’ migratory territory is related to climate change. Going back to the 1980s, sea turtles mostly went no farther north than Long Island Sound, off the coasts of New York and Connecticut, he said, but now some venture as far as the Gulf of Maine.
“The Gulf of Maine had its highest temperatures ever recorded in 2012, and it hasn’t gone down from there. . . . It’s a pretty fast-warming body of water,” Prescott said.
Prescott encouraged anyone who spots a sea turtle — dead or alive — to call Mass. Audubon at 508-349-2615 to help the organization track the creatures. And he asked that boaters exercise caution.
“If you’re on the water, you want to be careful because they are around,” Prescott said. “What is the expression? ‘Autopilot doesn’t see turtles’? ”
Jeremy C. Fox can be reached at email@example.com.