Ask a BioTech – All About Sea Turtles: Sea Turtle Nests
Sea turtle nesting season at Cape Hatteras National Seashore has begun! We reached out to our Biological Technician friends to learn more about the sea turtles that visit the Seashore each year. We are pleased to introduce you to Paul Doshkov, Supervisory Biological Technician (Bodie Island) and Scientific Research and Collecting Permit Coordinator at Cape Hatteras National Seashore, who this month answers your questions about sea turtle nests! This is Part I of a two-part series on sea turtles.
How do female sea turtles know where to lay their eggs?
It is believed that adult sea turtles return to the region where they were born, or their “natal beach.” They crawl up onto the beach and find the type of sand, density, slope and other conditions that they prefer. Precluding any disturbance to the turtle, she will dig the nest and lay her eggs. Sea turtles nest four to six times in a season, but only every two or three years. There are nests on Cape Hatteras National Seashore beaches every year, but not from the same sea turtles as the year before.
Adult sea turtles also rely on magnetic navigation, celestial cues, chemical concentrations in the water and memory of landmarks to assist them in finding their beach.
A loggerhead sea turtle crawl coming out of the ocean, leading biologists to the first nest of the season on Bodie Island. Photo: NPS/P. Doshkov.
At what age do female sea turtles lay their nest? How many eggs are in a single nest? How many eggs does a female sea turtle lay in the nesting season?
It depends on the species:
|Species||Age (years)||How often they nest (years)||Clutch Size (number of eggs)||Clutches/year||Time between clutches (days)|
How long does it take a sea turtle nest to hatch?
The average nest will hatch after 60-65 days. It can be a shorter period if the weather has been very warm or longer if:
- The weather has been cooler than usual.
- There is a lot of heavy rain (rain cools the nest).
- There is heavy overwash from the ocean.
When the nest is warm development speeds up, when it is cool development slows down.
How do the embryos breathe in the eggs?
A sea turtle embryo develops inside an eggshell that keeps it from drying out but allows for gas exchange. As the turtle develops, a chorioallantois membrane is formed that facilitates embryonic “breathing” by the process of diffusion. Movement of oxygen into the egg and carbon dioxide out of the egg is forced from an area of high concentration to low concentration. The carbon dioxide that is now in the nest cavity is diffused into the open air.
How long can hatchlings stay under the sand? What do they eat? How do they get out of the nest?
Once a turtle is pipped it remains in its shell to absorb the rest of its yolk and waits for its siblings to hatch, which may take up to two days. As a group, it is easier to climb out of the nest cavity. If they are alone, they usually become trapped and are not strong enough to climb out by themselves. It takes 24-48 hours for them to reach the surface once they start their trek.
Occasionally, sea turtles lay their nests in precarious locations, such this nest laid below the average high tide on Bodie Island Spit. If left in place, the nest would undoubtedly be washed over by the ocean multiple times, which would result in the drowning of the embryos and ultimately the loss of the nest. Seashore biologists have the option of relocating nests such as this to an area higher up the beach and farther from the ocean to give the nest a better chance of survival. This particular nest was subsequently relocated to a more suitable area nearby. Photo: NPS/P. Doshkov.
How do you know where the nest is?
Resource Management staff members at Cape Hatteras National Seashore patrol the beach every morning looking for the crawl tracks that sea turtles make while on land. These marks are formed by their flippers digging into the sand while pulling their weight up the beach. When these tracks are found, the staff members dig to verify the presence of eggs. The location is recorded by GPS, and a radio transponder ball is buried near the nest. After covering up the eggs, the area is enclosed to protect it from people, pets, and vehicles.
What type of sea turtles will hatch from the nests?
The most common species of nesting sea turtle at Cape Hatteras National Seashore is the loggerhead. We do get occasional green sea turtle nests and rarely, a leatherback or Kemp’s ridley sea turtle nest.
How can you tell if a sea turtle nest is going to hatch?
There are three signs to look for:
- Smell: The scent of the eggs clings to the hatchlings and can be smelled by humans 1-2 feet away up to half an hour before they emerge. Animals such as dogs and raccoons have a keen sense of smell and can smell the nest well before humans and much further away.
- Depression: A depression is created from sand and eggs getting stamped onto the floor of the nest.
- Temperature of nest cavity: The temperature will drop; some places have temperature probes to detect this change.
Sea Turtle Nest Safety Tips
- Dogs off leash have been known to dig into sea turtle nests. If a dog is loose when the hatchlings emerge, they may chase the hatchlings and injure them. Please keep your dog on a leash while spending time on Cape Hatteras National Seashore beaches.
- People have walked in or driven through sea turtle nest enclosures. The weight of stepping or driving on the nest can compact the sand making it difficult or even impossible for the hatchlings to dig out of the nest. Please avoid marked nest enclosures.
- All fireworks, including sparklers, are illegal on Cape Hatteras National Seashore beaches. The bright lights can cause sea turtle hatchlings to become disoriented when they emerge from their nests.
- If you are walking along the beaches of Cape Hatteras National Seashore at night and see a sea turtle hatchling repeatedly going the wrong direction (away from the ocean), please shine a small flashlight close to the ground in front of the hatchling to lead it to the surf. Never shine the light directly at the sea turtle hatchling!
- If you come across an injured, sick, or deceased sea turtle or sea turtle hatchling or a damaged sea turtle nest, please call the Cape Hatteras National Seashore Stranding Hotline at (252) 216-6892 and refrain from touching the sea turtle, hatchling or nest.
To learn more about the sea turtles that call Cape Hatteras National Seashore home, click here.
Paul has served as a Biological Science Technician at Cape Hatteras National Seashore for 15 field seasons and is primarily involved with shorebird management, sea turtle management and marine mammal (whales, dolphins, porpoises, seals and the occasional manatee) stranding coordination including seal observations during the winter months. Paul is based out of Nags Head near Coquina Beach and has also recently began coordinating the Seashore’s Research and Collecting Permit program. For any interest in conducting research on the Seashore, please contact Paul at firstname.lastname@example.org.