Riverhead marine life experts responded to two sightings of dead leatherback sea turtles Wednesday, including one in Southampton.
One was reported at about 1 p.m. at the end of Atterbury Road in Southampton, leading into Shinnecock Bay.
"It probably had been deceased for over 24 hours," said Kimberly Dunham, Rescue Program director for the Riverhead Foundation. "It was an adult male approximately seven feet in length and, based on its size . . . 700-plus pounds."
The animal appeared to have been struck by a propeller blade, she said.
"There was a very significant laceration to the carapace" or the top of the shell, Dunham said. "The damage to the shell was consistent with a propeller strike and it would have been a mortal strike."
A crew of researchers from the foundation had also been called to the South Beach boardwalk in Staten Island at about 11 a.m. Wednesday, where they discovered another carcass of a leatherback sea turtle, said Dunham.
"It was fairly decomposed," she said, adding that the experts took samples from the body, but have not yet determined the cause of death.
Dunham said that the leatherback sea turtles feed on jellyfish, which have been particularly numerous near the shores this year.
"This is the time of year that sea turtles are in our area," she said, including other types of sea turtles. "The leatherback gets all the attention. They're just big, amazing animals."