Cape Cod Corral

How sea turtles are getting trapped in Cape Cod Bay, and how science is saving them

A 32-degree breeze chilled the coastline of Eastham as staff of the Mass Audubon’s Wellfleet Bay Wildlife Sanctuary (WBWS) waded into the ocean. I watched alongside other volunteers through the small gap between my scarf and winter hat as they reached toward a motionless sea turtle floating in the choppy surf—like a leaf being tossed in the wind. The turtle was one among hundreds belonging to an unlucky cohort that washes ashore Cape Cod beaches every year when the water temperature plummets, but it is because of institutions like WBWS that sea turtle mortality along Cape Cod can be considered a success story.

The path is not certain, but perhaps following the warm Gulf Stream waters northward, juvenile Kemp’s ridley, loggerhead, and green sea turtles are drawn to the Gulf of Main and Cape Cod Bay’s nutrient-rich waters every year during the warm summer months while feasting on local crabs, shellfish, marine vegetation and other fruits de mer until late fall—an Old Country Buffet for sea turtles. By November, however, hundreds of these critically endangered and threatened turtles wash up on Cape Cod shorelines either dead or entirely incapacitated, as victims of the little-known phenomenon of cold-stunning.

Part of this anomaly is described by the physiology of reptiles; a sea turtle’s body temperature is regulated by the temperature of their environment. Like a car engine, turtles are susceptible to overheating in extreme heat or losing function in the cold. Cold temperatures cause decreased circulation and nerve function, and lethargy, rendering the turtles immobile—subject to the mercy of winds and currents. As water temperatures begin to fall, sea turtles typically migrate to warmer, southern waters; however, the distinctive arm-shaped geography stretching from Sandwich to Provincetown traps turtles within Cape Cod Bay, making it difficult to navigate back to open waters.

The geographic labyrinth of Cape Cod and dropping water temperatures work in concert to corral and create hypothermic conditions for sea turtles. In 2014, Cape Cod experienced its largest stranding event of over 1,200 sea turtles; 2018 got off to an early start and reached well over 600 strandings by the end of November. Thanksgiving proved to be especially deadly, bringing in a staggering 220 dead, cold-stunned sea turtles, almost all of which were Kemp’s ridleys. “November 22^nd was the coldest Thanksgiving in a decade,” according to Bob Prescott, founder of Wellfleet Bay Wildlife Sanctuary’s sea turtle rescue initiative. “An unusual storm system caught [the sea turtles]. Such a precipitous drop in air temperature is lethal for these animals when they wash ashore.”

The numbers of sea turtles stranding on Cape Cod have been steadily increasing, and scientists point to climate change as the main culprit. The Gulf of Maine is the most rapidly warming ocean basin in the world, recording a temperature of 68.93°F in August of 2018, according to an ocean surface temperature report by NASA’s Earth Observatory. Temperature and turtles work in tandem: As water temperature increases in the north, sea turtles follow. However, as the summer season ends and waters gradually cool, sea turtles may not make it south quick enough to avoid getting caught in a seasonal cold-snap. 

Scientists across Massachusetts are working against the clock—and the tides—to find answers about these species, and they have an arsenal of tools at their disposal. Dr. Maureen Conte of the Ecosystems Center of the Marine Biological Laboratory (MBL) in Woods Hole plays a key role in this research, using biochemistry as a way to learn more about cold stunning. Conte specializes in lipid and stable isotopic analysis at MBL, using tissues from dead sea turtles to peek into each turtle’s personal history. The chemical signature of each tissue and turtle provides unique, individual-specific information, like a barcode, using chemicals in the turtle’s tissues to identify what the turtle was eating, where it has been, if it was starving, how far it migrated, etc. “Lipid composition and stable isotopes ultimately help us understand how sea turtles use Cape Cod waters as a habitat,” says Conte. “Cape Cod is very unique because we have access to a critically endangered, enigmatic species (Kemp’s ridley), and this research helps us learn how to effectively manage these animals.”

The research doesn’t end in Cape Cod though—many major institutions are processing data from Cape Cod’s cold-stunned turtles, including Yale University, NOAA research laboratories in Woods Hole, Mississippi and Seattle, and locations even as far as South Africa. “We collaborate with a lot of different research groups,” shares Bob Prescott. “[Scientific research] is one of the great benefits of having access to these turtles. We now have access to knowledge about an animal that is very difficult to study, which is very valuable in deciding how to manage them.” The work emerging from labs across the country is being used to inform conservation efforts that may see legislation involving how to partition land protection to support conservation.

On the frontlines of the sea turtle rescue initiative is the staff at Wellfleet Bay Wildlife Sanctuary and an army of volunteers patrolling beaches at crucial times. “Every year since 2014, we prepare to receive 1,200 turtles,” Prescott says. “We need to be equipped to process large numbers of turtles at a moment’s notice, just like we saw on Thanksgiving this past year.”

The volunteer network involved in sea turtle rescue is admirable and remarkably effective. With a head count of 200-225 loyal volunteers, the Cape Cod locals donate their time to comb beaches day and night in search of cold-stunned turtles from late October through December. A distinct local interest and compassion for these endangered creatures is what makes sea turtle recovery and rescue on the Cape so successful. According to Prescott, about 85 percent of cold-stunned sea turtles that survive the first 24-48 hours after rescue will recover—these odds are made possible by the participation of vigilant citizens who find the turtles before it is too late, providing hundreds of extra eyes and mobilizing action across the Cape.

Local involvement in sea turtle recovery is a testament to the power of citizen science. An interest in the natural world brings hundreds into the Wellfleet Bay Wildlife Sanctuary nature center every year. With a full schedule of educational programs that explore local wildlife and train volunteers, WBWS prioritizes education and uses the natural world to bring awareness to urgent issues. The vigor and initiative of the staff and volunteers is a refreshing reminder of the privilege it is to live on Cape Cod, and the responsibilities we all share in protecting the natural world. 

The approval of a Massachusetts Environmental Trust grant for sea turtle research, partnering Wellfleet Bay Wildlife Sanctuary with Coonamessett Farm Foundation, NOAA Northeast Fisheries Science Center and the Marine Biological Laboratory, is promising for the dire situation facing Cape Cod’s unlucky late-season visitors. However, the sobering reality of this issue is that there is no immediate solution, only ways to better prepare and act more efficiently to reduce the number of turtle fatalities when late fall arrives.

With the Gulf of Maine warming faster than any other oceanic region in the world, global climate change is the hand that bids turtles farther north every year, and its palm tells an unsure future. Since there is no immediate solution to turtle cold-stunning, citizen science is at the crux of the turtle-rescue initiative on Cape Cod; thus we all play a crucial role in deciding the fate of these sea turtles.