Cold Stunning Causes & Effects

Cold stunning is when sea turtles become weak and prone to health issues after being exposed to rapidly cooling waters. This typically occurs in late fall when water temperatures drop below 50 degrees. While sea turtles may recover quickly from a brief chill, if they're exposed to icy water over several days, it can be life threatening.

What Happens When Sea Turtles Become Cold-Stunned?

Cold-stunned sea turtles are weak, disoriented and unable to regulate their buoyancy. Sea Turtles in this condition often float to the water's surface, where they're vulnerable to predators, boat strikes and injuries. These sick and injured sea turtles can wash up on the shore and become stranded.

Cold-stunned turtles have weakened immune systems and a range of health issues. These issues can include infections, lesions and parasites. Young sea turtles are more likely to suffer the effects of cold stunning. They're also more likely to require human care to survive.

Why Does Cold Water Affect Sea Turtles?

Sea turtles, like other reptiles, are ectotherms. This means that their body temperature isn't internally regulated. Instead, they move to warm waters when they're cold and retreat to cooler waters when they're overheated. In general, sea turtles prefer water and air temperatures ranging from the low 60s to high 80s.

What is a Cold-Stunning Event?

A cold-stunning event is when many sea turtles are affected at the same time in the same area. This can be caused by a sharp, extended drop in air and water temperatures. These events most often occur in shallow bays and lagoons, and in areas where geography blocks a sea turtle's path to warmer water.

Map Showing the Common U.S. Sea Turtle Stranding Locations along the East Coast

In the United States, cold-stunning events tend to happen in these areas:

  • Cape Cod Bay, Massachusetts
  • Long Island Sound, New York
  • Pamlico Sound, North Carolina
  • Mosquito Lagoon and areas around the Indian River Lagoon, Florida
  • St. Joseph Bay, Florida
  • Bays in Texas (including Corpus Christi Bay, Matagorda Bay, Laguna Madre)

Cold-Stunned Sea Turtle Rescue

Each fall, representatives from organizations such as Massachusetts Audubon Wellfleet Bay Wildlife Sanctuary Volunteers patrol areas where stranding events have become common. These volunteers walk the beaches of Cape Cod looking for sea turtles. When they find one, they transport it to a nearby triage facility such as the New England Aquarium where veterinary staff assess it. Sometimes, volunteers must address emergency issues on the spot. Once a sea turtle patient is stable, volunteers can transport it to a facility like the National Aquarium for long-term rehab and care.

Experts at a network of rescue and rehabilitation facilities provide care for rescued sea turtles in need of treatment. These facilities are located across the country, but mostly along the East Coast. When the seasons change and temperatures drop, these organizations, including National Aquarium Animal Rescue, are on standby awaiting the arrival of cold-stunned sea turtles. These teams sometimes receive and begin treating cold-stunned sea turtles within 24 hours of their rescue. This quick response helps speed sea turtles' recovery.

Warming Ocean, Cold Turtles

As ocean temperatures continue to rise due to climate change, sea turtles follow warmer waters further and further north in summer. This often takes them beyond their traditional migratory routes. This puts them at risk of being too far north when fall arrives. Others become disoriented and trapped by geological features of coastlines, unable to make their way south.

The Gulf of Maine, which is bounded to the north by Cape Sable Island on the tip of Nova Scotia and to the south by Cape Cod, continues to warm faster than almost any place else on the planet. Sea turtles drawn there by warm water and abundant food can be caught by wintry weather and face a truly challenging route back to the southern Atlantic. This explains why so many of the sea turtles treated at the National Aquarium come to us from the crook of Cape Cod, where the geography can trap turtles as they attempt to head south from the Gulf of Maine.

Are Cold-Stunning Events Happening More Often?

People observed and recorded cold-stunning events as early as the 1880s. While cold-stunning events are not perfectly consistent year after year in any one location, they are occurring more frequently. As ocean temperatures rise at an unprecedented rate, scientists are seeing more sea turtles in areas where they're at risk of cold stunning.

This increase may be related to growing sea turtle populations thanks to conservation efforts. However, combined with rising ocean temperatures, it has set the stage for more frequent and more intense cold-stun seasons.

According to data from Mass Audubon, the number of cold-stunned sea turtles in the Northeast has increased dramatically over the past 10 years—and it's not expected to slow any time soon. Experts predict that by 2031, more than 2,300 sea turtles may experience cold stunning annually on Cape Cod.

What Should I Do if I See a Stranded Sea Turtle?

Through a federal permit from the National Oceanographic and Atmospheric Administration (NOAA), the National Aquarium manages sea turtle and marine mammal rescue response in our region. If you encounter a sick or stranded sea turtle in the mid-Atlantic, call our team at 410-576-3880. Please be prepared to share your location and a description of the sea turtle and its condition. This will help us determine if it's in need of medical attention or just resting. Even if you're not sure the sea turtle is in distress, we are still interested in knowing about sightings. We continue to learn about animal populations in our area and how these animals use our beaches and waterways. If the sea turtle is sick or injured, National Aquarium Animal Rescue will respond and transport it to the Aquarium in Baltimore for rehabilitation. Elsewhere, you can contact your state's natural resources agency for information about animal rescue in your area. NOAA Fisheries also offers a resource for reporting a stranded or injured marine animal.

How Can You Help?

Wherever you live, you can give rescued sea turtles a fighting chance by supporting legislation to help fund rescue efforts. Legislation like the bipartisan Sea Turtle Rescue Assistance Act will use federal funds to aid organizations working to maintain sea turtle populations.

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