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Sea Turtles Face Challenges in Warming Waters

Photo © Esther Horvath. Lea Desrochers, Turtle Research Assistant at Mass Audubon’s Wellfleet Bay Wildlife Sanctuary rescues a Kemp’s Ridley sea turtle at at Corn Hill Beach, Truro, MA.

Every November and December, for more than 30 years, sea turtles strand on the bayside beaches of Cape Cod. At first there were only a few. But since 1999, hundreds of turtles have washed ashore each year. In 2014, more than 1,200 sea turtles were rescued or recovered.

Cold Stunning in Cape Cod Bay

Sea turtles strand on the Cape in the fall because of “cold-stunning”, a kind of hypothermia. Most are young Kemp’s Ridleys, the most endangered sea turtle in the world, transported north by the Gulf Stream. Ridleys feed along the New England coast during the summer. As they move south in the fall, some may become trapped by the hook shape of Cape Cod. Unable to find their way out of the bay and chilled by falling temperatures, turtles’ systems start to shut down.

For years, the staff and volunteers at Mass Audubon’s Wellfleet Bay Wildlife Sanctuary have patrolled beaches to rescue cold-stunned turtles and transport them to the New England Aquarium for lifesaving medical care. Most of the rescued turtles will eventually return to the ocean. 

Warming Waters May Play a Role

Before 1990, sea turtles generally didn’t travel north of Cape Cod because the water was too cold. Young turtles making return trips south in the fall would cold-stun on Long Island, New York, but rarely along the Massachusetts coast. That started changing in the 1990’s. Since then, the Gulf of Maine, which includes Cape Cod Bay, has been warming even faster than the global average. Warmer waters have encouraged sea turtles and many other forms of marine life to take advantage of abundant food resources in New England and even eastern Canada. Unfortunately, for some turtles, the outstretched arm of the Cape can be a deadly trap.

Warming Temperatures Pose More Threats

Green Sea Turtle covering a nest. Photo © United States National Park Services.

Climate change threatens sea turtles well beyond Cape Cod. Warming temperatures on nesting beaches, especially those in tropical regions, could skew sea turtle sex ratios since a hatchling’s sex is determined by the incubation temperature of its nest. Warmer nest temperatures tend to produce females and, in some locations, nests are producing too few males. If the sand at a nesting beach becomes too hot, it can weaken hatchlings or even kill them. Nesting turtles can also be overcome by heat in the process of digging their nests or laying eggs.

And the beaches turtles use to nest are themselves at risk. The increasing rate of sea level rise, more intense coastal storms, erosion, and flooding are likely to accelerate the loss of sea turtle nesting habitat.

Hope for these Resilient Reptiles

Sea turtles have been on the planet for 100 million years and managed to survive the mass extinction that killed the dinosaurs. But can they survive all the human-made problems that confront them? Sea turtles are also threatened by ocean pollution, entanglement in fishing gear, and extensive development along their nesting beaches. The good news is that sea turtle populations have been bolstered with help from conservationists, including Mass Audubon, and there are significant legal protections in place for them. There’s been progress, but a great deal of work remains.

A cold-stunned sea turtle that washes up on a Cape Cod beach has already dodged a number of obstacles in its life. Rescuing that turtle supports a second chance at survival. But we also have a special opportunity to make a difference in helping it to overcome larger challenges like climate change.

Jenette Kerr, Wellfleet Bay’s Marketing and Communications Coordinator.

Rescuing Sea Turtles on Cape Cod

As winter approaches, the water temperature of Cape Cod Bay slowly drops, and sea turtles should make their way south to warmer tropical waters. However, each year since the late 1970s, some juvenile turtles do not make the journey in time. Trapped by the hook of the Cape, the turtles become disoriented. When the water reaches about 50° by mid-November, the turtles are too cold to eat, drink, or swim, and become “cold-stunned.”

Maureen Duffy, a member of the Wellfleet Bay Turtle Team, monitors a rescued Kemp’s Ridley sea turtle.

And every year, staff and volunteers from Wellfleet Bay Wildlife Sanctuary patrol the beaches, rescuing these turtles. This year is no different. Since the season began earlier this fall, Wellfleet has encountered more than 630 cold stunned sea turtles.

During the Thanksgiving freeze, when temperatures plummeted overnight, more than 220 endangered sea turtles stranded on Cape Cod. Wellfleet Bay’s dedicated team of rescuers patrolled the beaches day and night in search of cold-stunned turtles trapped in the surf, and had to deal with the full force of the weather for more than 48 hours straight.

Of the 220, only approximately 50 were alive when rushed to the wildlife sanctuary’s turtle intake unit for weighing, measuring, and assessment. Volunteer drivers were lined up to transport the turtles to the Animal Care Center in Quincy operated by the New England Aquarium, Mass Audubon’s partner in this important rescue-and-rehabilitation mission.

Typically, cold-stunned turtles rescued in November are still alive with a very good chance of recovery. But the unusual cold-snap produced conditions more common in late December when most of the turtles that strand are dead.

Wellfleet Bay Wildlife Sanctuary Director Bob Prescott, who has been monitoring sea turtles for more than 35 years, notes climate change is causing more and more strandings. Back in the 1980s and 1990s, the water in the Gulf of Maine was too cold for sea turtles. But warming ocean temperatures have allowed sea turtles to enter the Gulf of Maine and some cannot get out before the water temperature drops.

There’s still several months left in the season and the team on the Cape will be hard at work. Be sure to follow Wellfleet Bay on Facebook for the latest information. You can also learn more about sea turtles and how to support the Sea Turtle Rescue Project.