Metro

Turtle rescuers blame climate change, geography for unprecedented stranding numbers

A Wellfleet Bay staff member, Maureen Duffy, observed a Kemp’s ridley turtle that survived.
Mass Audubon Wellfleet Bay Wildlife Sanctuary
A Wellfleet Bay staff member, Maureen Duffy, observed a Kemp’s ridley turtle that survived.

When animal rescuers and volunteers arrived at Cape Cod beaches during a three-day span this week, they were expecting to find some cold, stranded turtles — but not more than 220 of them.

From Wednesday to Friday afternoon, 227 turtles were found stranded on Cape beaches, primarily in Brewster and Wellfleet, Mass Audubon spokesman Michael O’Connor said. Of that number, 54 of the turtles were alive, O’Connor said.

Almost all the stranded reptiles were Kemp’s ridley sea turtles, but there were several green turtles as well, O’Connor said. About 440 turtles have been stranded on the Cape since October, he added.

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Bob Prescott, the director of the Mass Audubon Wellfleet Bay Wildlife Sanctuary, which has been leading turtle rescue efforts on Cape Cod for more than 30 years, suggested the number of turtle strandings this week is unprecedented.

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“We’ve never had anything like that before,” he said.

The number of sea turtle strandings around Cape Cod has risen exponentially over the past five years, and experts say climate change seems to be a major catalyst for the trend that Prescott has dubbed “turtlegeddon.”

In the 1990s, wildlife rescuers were responding to 30 to 50 sea turtle strandings around Cape Cod every sea turtle season, which is between November and December. That number jumped to 80 to 100 strandings by the 2000s.

The rate of strandings rose again around 2011 and peaked in 2014, when about 1,200 sea turtles stranded over a two-month stretch, officials said.

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Since that outlier year, the average has been about 400 strandings per sea turtle season. This season, that average has been surpassed, Prescott said, and there’s still about a week to go before December.

“Up until 2014, our record for a day was in the low 30s,” said Tony LaCasse, spokesman for the New England Aquarium, which treats many stranded turtles at its sea turtle hospital in Quincy. “Now we have days when we have 80 to 100 a couple of times a year.”

The Cape’s unique geography is the greatest contributor to marine animal strandings in Massachusetts, but the number of incidents has skyrocketed recently because ocean temperatures are generally warmer, meaning that Cape Cod waters aren’t getting colder until later in the fall every year, Prescott said.

“Turtles live in Cape Cod Bay through the summer, having a great time, and by the time the weather changes, they’re compromised and can’t migrate, and when winds pick up, they strand,” Prescott said.

Sea turtles can go as far north as the Gulf of Maine, which is the fastest-warming body of water in the world right now, Prescott said. Turtles swim and feed there, thriving in the warm water, and when temperatures begin to drop to around 50 degrees, they head south and become hopelessly trapped by the Cape’s signature hook, causing chronic hypothermia.

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“They can’t figure out the way out until they’re already compromised,” Prescott said. “In September, they could probably get around it. In November, they can’t.”

Sea turtles, while not alone in their strandings, are the only species that has seen a significant increase in the number of strandings around Cape Cod as a result of climate change.

Fish also have optimum water temperatures that they need to live in to survive, but they’re much more resilient, LaCasse said.

Ocean sunfish, sand tiger sharks, saury bait fish, and shortfin squids have also been known to strand when water temperatures drop, but not to the same extent as sea turtles, Prescott said.

The kind of turtle that washes up most commonly in Massachusetts, Kemp’s ridley sea turtles, are the smallest kind of sea turtle and the most endangered. The turtles that washed up just before Thanksgiving were almost all Kemp’s ridleys, with the exception of three green sea turtles and one loggerhead sea turtle, officials said.

But because so many of the sea turtles that strand are so young, their deaths on shore don’t have a huge effect on overall population numbers.

So despite the increased strandings, sea turtles are doing relatively well. They were close to extinction in the 1940s, and over the decades, thanks to increased global awareness, changing fishing policy, and more active turtle search and rescue teams, sea turtles have started making a comeback, LaCasse said.

“The prognosis is for turtles to continue to do well and recover, and 20 years from now, we’ll look back and say, ‘That was a tough Thanksgiving. We lost a lot of turtles, but that was the only one that happened,’ ” Prescott said.

Danny McDonald of the Globe staff contributed to this report. Andres Picon can be reached at andres.picon@globe.com. Follow him on Twitter at @andpicon.