Cold-Stunning and Sea Turtles – Frequently Asked Questions

What does “cold-stunning” mean?

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Cold-stunning is a condition in which sea turtles become very weak and inactive from exposure to cold temperatures. It generally occurs when water temperatures fall below 50˚F (10˚C) where sea turtles are present. Cold-stunned turtles become lethargic and are eventually unable to swim causing them to float at the surface. Wind and/or tides may wash them ashore. If temperatures remain low or turtles are not rescued, they can develop secondary health problems or die. Hundreds or even thousands of sea turtles can be affected by cold-stunning events.

Why do sea turtles become cold-stunned?

As reptiles, sea turtles are not able to strictly regulate their body temperature like mammals and birds do. With several physiological adaptations, the leatherback sea turtle comes the closest to being able to do this. For other sea turtle species, their body temperature is closely related to the environment, which in some areas requires them to seek out warmer water during winter months. They do this by swimming away from shore to deep water or by migrating south. If water temperatures fall below 50˚F (10˚C) and turtles are present in the area, they are at great risk of becoming cold-stunned.

Cold-stunning happens most commonly in specific coastal areas of the U.S. Atlantic and Gulf of Mexico. In general, cold-stunning follows winter weather that causes sudden and prolonged decreases in water temperature. The characteristics of water bodies also plays a role. Cold-stunning is most likely to occur in shallow bays and lagoons where water temperatures can fall relatively quickly, as well as in areas where access to warmer water is limited or obstructed by the surrounding land.

What factors influence cold-stunning events?

Cold-stunning events occur in some years, but not others, and can drastically vary in numbers of turtles affected.  Significant contributing factors include the severity of winter weather events and abundance of turtles within areas of cold water temperatures. However, we do not fully understand why some turtles stay within areas prone to cold-stunning and why others migrate into warmer waters.

How does cold-stunning effect sea turtles?

Cold-stunning can affect sea turtles in different ways depending on how cold they get and for how long. In general, the colder the temperature and the longer the duration, the worse the effects. 

Sea turtles can recover quickly from brief exposures to cold temperatures near the 50˚F (10˚C) threshold with little long-lasting effect. This is common in cold-stunning events that occur in the southeastern U.S. As cold-stunned turtles become lethargic and float to the surface, they are exposed to cold air temperatures, which may worsen their condition, and cause them to drown. Cold-stunned turtle are also vulnerable to predators. 

With colder or more prolonged conditions, as are encountered in the northeastern U.S., sea turtles tend to become more debilitated. This level of cold exposure affects circulation, organ function, and the immune system, and can directly damage the skin, shell, and eyes.  Opportunistic bacterial and fungal infections are common in severely affected turtles.

Where does cold-stunning occur?

Locations where cold-stunning events have repeatedly occurred in recent decades include:

• Cape Cod Bay, Massachusetts;
• Long Island Sound, New York;
• Pamlico Sound, North Carolina;
• Mosquito Lagoon and surrounding areas of the Indian River Lagoon, Florida;
• St. Joseph Bay, Florida; and
• Bays statewide, Texas (including Corpus Christi Bay, Matagorda Bay, Upper/Lower Laguna Madre).

Cold-stunning can happen in other areas during atypical, extreme cold weather events. For example, in 2010 unusually severe cold weather resulted in cold-stunning throughout the state of Florida, including the Florida Keys.

What can be done to help cold-stunned sea turtles?

Cold-stunned sea turtles often require help from people to recover and protect them from the elements. This may include a short stay in captivity until waters warm or transport to a warmer location for release. Severely affected turtles often require veterinary care and rehabilitation before they can be returned to the wild. 

Fortunately, the U.S. has a well-established network of government agencies, wildlife organizations, and volunteers that come together to help sea turtles during cold-stunning events. This network actively plans for cold-stunning events and has alert systems to help organize and deploy people to look for and assist cold-stunned turtles.

Please remember that all sea turtles are threatened or endangered under the U.S. Endangered Species Act; therefore, a permit is required to work with them.

Can cold-stunning be prevented?

No, there is no way to prevent cold-stunning events.  As all sea turtles are threatened or endangered species under the U.S. Endangered Species Act, the goal of response to these events is to save as many turtles as feasible and return them to the wild. This goal requires substantial efforts by a collective network of government wildlife agencies, rehabilitation facilities, stranding organizations, and volunteers.

Are cold-stunning events a new phenomenon?

No. Cold-stunning events were documented in the late 1800’s and are among some of the first accounts of sea turtles in the U.S. There have been considerable changes in sea turtle populations over the last hundred years that may have contributed to the frequency and magnitude of cold-stunning events over time. Some populations have grown in recent years as a result of conservation efforts, and numbers affected by cold-stunning events have also grown larger. Nonetheless, there are many unanswered questions about factors that influence the size and occurrence of cold-stunning events. For example, recent research in the northeastern U.S. suggests that warming sea temperature may be influencing sea turtle movements in a way that increases the chances of cold-stunning.

What do I do if I see a stranded sea turtle?

If you see a sick, injured, stranded, or dead marine mammal or sea turtle, immediately contact your local stranding network.