Can Sea Turtles Get Too Cold During the Winter in North Carolina?

This post was written by University Communications intern, and NC State student, Erin Ferrare.

With colder months moving in, changing water temperatures off the coast of North Carolina pose a threat to sea turtles who live off the coast of the Tar Heel state. Cold shock, also known as cold stun, is a condition that affects sea turtles and causes them to become very weak and unable to swim.

To learn more, we talked to Dr. Craig Harms, professor in the Department of Clinical Sciences and Director of the Marine Health Program at the North Carolina State University Center for Marine Sciences and Technology (CMAST). Harms also provides veterinary services and support at the Karen Beasley Sea Turtle Rescue and Rehabilitation Center.

What kind of sea turtles live off the coast of North Carolina?

“We have three to five species of sea turtle that are found off the coast of North Carolina,” Harms says. “The ones commonly found are loggerheads, which feed and nest here. Then we also have green sea turtles, which rarely nest but as juveniles are coming into the sounds to feed. This is also like Kemp’s ridley, which almost never nest here but are very common in the summertime for growing and maturing.”

While those are the three main species that are common off the coast, other species make an appearance every now and then. Leatherback sea turtles migrate past North Carolina between their breeding grounds in Florida and the Caribbean and their feeding grounds close to the Chesapeake Bay. They can even go as far north as Nova Scotia, Canada, to reach good feeding locations. Also, hawksbill sea turtles are generally found in warmer tropical and subtropical waters, but there have been a few recorded cases of their nests on the sandy beaches of North Carolina.

What is cold shock?

“It is basically hypothermia in sea turtles, so they get too cold for them to operate,” Harms says. “They are cold-blooded, which is an advantage since they can operate at several different body temperatures without expending a lot of extra energy to maintain their metabolic rate. But at some point, it gets too cold for their cells to operate efficiently, and they just shut down.”

That’s when the cold shock sets in, which normally happens when the water temperature is around 53 to 59 degrees Fahrenheit. If the water temperature drops rapidly, like it does in the shallow waters in the sounds of North Carolina, the turtles are more likely to develop cold shock at a slightly higher temperature than they otherwise would.

What happens to a turtle when it has cold shock?

Sea turtles can’t stop cold shock from happening when the process starts, so how does the condition really effect the animal?

“When sea turtles cold stun they really just shut down,” Harms says. “Fortunately, their reflexes are good, and they can grab a lung-full of air so that they float on the surface of the water. They also can lift their head above the surface as the last reflex before they are completely stuck, which helps for breathing.”

These reflexes help with the rewarming process, because if the turtle stays on the surface of the water they are in direct sunlight. Even if the water is cold, if the sun comes out the turtles have a chance to warm up and hopefully swim toward warmer waters.

Now, imagine you’re on a nice beach in North Carolina during the winter months and you see a turtle laying on the shore. What are some symptoms to check for to see if this turtle is in cold shock?

“You can almost always assume that a turtle on a beach in the winter has cold shock,” Harms says. “It depends on the environmental conditions, but if you see a turtle on the beach, you can assume that this is a case of cold shock. In the ‘transition months’ it’s not a sure thing.”

One clue Harms mentions is to look at the number of turtles on the shore. If it is a single turtle there might be some other factor that led to its stranding but if there are numerous turtles it is more likely to be a cold shock event.

The turtles will feel cold to the touch and have little reactions to being touched. They also might sustain injuries in the surf because once a turtle is in cold shock it gets tossed around by the waves and surf wherever they are.

How do veterinarians treat cold shocked turtles?

The first step is getting the turtles from the beach to the treatment facilities, which include CMAST, the Karen Beasley Sea Turtle Rescue and Rehabilitation Center, and the Sea Turtle Assistance and Rehabilitation (STAR) Center on Roanoke Island.

“Getting the turtles to the facilities might include driving them or taking a boat because we get a lot of cold shocked turtles from Cape Lookout National Seashore,” Harms says. “Within that whole transfer process, it’s important not to warm the turtles up too fast. When that happens, a reperfusion injury might occur which is when the affected tissue suddenly gets circulation quickly and this can cause problems.”

When the turtles make it to the facility the veterinary teams start the turtles close to the temperature they are at when they arrive, so that the turtles do not heat up too quickly. When cold shock occurs, these are typically “mass casualty events,” which means there can be 50 or more turtles at once, so the doctors split the animals up into treatment groups.

“Step one is thermal control and making sure the turtles’ temperatures come up gradually,” Harms says. “Step two is getting blood samples from a representative proportion of the turtles to see if there are any fluid or electrolyte imbalances. We tailor fluid therapy for each group. Finally, we focus on any individual problems like injuries the turtles might have obtained in the stranding process.”

There are two different types of cold shock according to Harms: acute cold shock and chronic cold shock. Acute cold shock sea turtles are the ones who are otherwise healthy and doing great and don’t need much medical attention other than a slow warming up. Chronic cold shock means that the sea turtle has been out in the water for some time and might have gone through a few cycles of warming and cooling. They typically are not in good nutritional health and could have complications emerge from the cold shock process, including bacterial and fungal infections.

“The number of turtles every year fluctuates wildly,” Harms says. “We’ve had over 100 turtles one year and then in the low dozens as well. Usually there are more cold shock cases in Cape Cod, Massachusetts but sometimes North Carolina has the most depending on when the cold weather hits.”

What do you do if you find a cold shocked turtle?

In North Carolina there are multiple stranding hotlines to call including the official North Carolina Sea Turtle Stranding Hotline (252-241-7367), along with area-specific hotlines that include Ocracoke & Hatteras Island (252-216-6892), Oregon Inlet (252-441-8622), and Wrightsville Beach (833-488-7853).