First ‘cold-stunned’ sea turtles of the season wash up on Cape Cod

A Kemp’s ridley sea turtle at the New England Aquarium's Animal Care Center in Quincy, in 2010.Globe Staff/file

Four endangered sea turtles were found stranded along beaches in Eastham and Brewster on Monday, marking the beginning of “cold stun” season along Cape Cod, officials said.

Staff members from Mass Audubon’s Wellfleet Bay Wildlife Sanctuary rescued the turtles and brought most of them to the New England Aquarium’s Animal Care Center in Quincy, where they will receive treatment before being released back into the wild, officials said.

Cold stunning — a hypothermic reaction caused by prolonged exposure to cold water temperatures — can be fatal in turtles, according to the National Oceanic and Atmospheric Administration. The condition is marked by decreased circulation and heart rate, as well as lethargy.

All four rescued animals were Kemp’s ridley sea turtles, the most endangered of the eight species of sea turtle, according to Mass Audubon spokeswoman Jenette Kerr.

Kemp’s ridleys feed in Cape Cod Bay during the summer, but become trapped by the Cape’s hook-shaped geography, Kerr said. Unable to make their way south, the turtles begin to suffer from lowered body temperatures and stop actively swimming.

“That’s when a strong wind can bring them ashore,” Kerr said.

Cold-stun strandings don’t usually begin until the surface temperature of Cape Cod Bay drops to 50 degrees, but started at higher temperatures the past two years.

“At the moment, the bay’s just a smidgen above 57 [degrees] so we figured we had a week or so before we’d see turtles strand,” Kerr said. “The cold front that moved in Sunday afternoon probably helped things along.”

Last year, a total of 420 cold-stunned sea turtles washed up along Cape Cod beaches, officials said. About 80 percent were Kemp’s ridleys.

Sea turtle strandings in the fall have been rising since 1979, officials said, with the record set in 2014. It’s not clear what is causing the increase, although warmer waters in the Gulf of Maine could be a factor.

Three healthy Kemp’s ridleys were also spotted near Cape Cod in the past couple of weeks, Kerr said.

“These weren’t cold-stunned turtles, but finding them (which is pretty unusual) suggested that the coming rescue season could be a busy one,” she said. “However, it is not an exact science by any means!”