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This Month in Science: Sea Turtle Season

Baby sea turtles are currently hatching all along the North Carolina coast. Sea turtle nesting season runs from April to September, and peaks during the month of June1. As of August 17, 2018, 770 nests have been cataloged this season by the North Carolina Wildlife Resources Commission. There are four species of sea turtles (loggerheads, leatherbacks, greens, and Kemp’s Ridleys) that nest on the coast of North Carolina, but the majority of the nests (738) are loggerhead turtles.

Loggerhead turtles, scientific name Caretta caretta, get their name because of their very large heads2. They have reddish-brown heart-shaped shells that can grow up to 3.5 feet in length and typically weigh between 155 and 375 pounds. Loggerheads have very strong jaws that allow them to eat hard-shelled fish like horseshoe crabs and mussels1.

It takes about 30 years for a female to reach sexual maturity. Once mature, females will travel back to the beaches where they hatched to make their own nests and lay their eggs3. In some cases, this means the turtle will travel hundreds to thousands of miles to return “home”. A mature female will only nest in spring or summer every two to four years, but they will nest multiple times in that season. She will lay 100-126 eggs per nest4. Almost half of nesting attempts will result in a false crawl- when a sea turtle climbs onto the beach, but returns to the ocean without nesting. Although researchers are not certain as to why this occurs, it is thought that something (predators, human activity, excessive lighting) disturbs their nesting behavior, prompting them to return to the ocean and try again at another time5. After nesting, the female returns to the ocean, leaving her offspring to fend for themselves.

The temperature of the nest determines whether the hatchlings will be male (82°F) or female (89°F)6. Temperatures in between that range will produce a nest of mixed male and female hatchlings. Eggs take about 60 days to incubate in the nest before hatching. Hatchlings will break out of their eggs and remain in the nest for a few days to absorb their yolk. The yolk gives them the energy they will need trek into the ocean and deeper waters7.

Once they reach the water, loggerheads will migrate thousands of miles to get to the safety of the open ocean, often within the Sargasso Sea located between the United States and the west coast of Africa within the Atlantic Ocean. This migration is extremely dangerous, and it is estimated that only 0.1%-0.4% of turtle hatchlings will survive the journey8. Because the hatchlings are not strong enough to dive, they must remain at the surface, making them particularly vulnerable to coastal predators.

How exactly does a baby turtle navigate the open ocean without any guidance? Loggerhead turtles are born with an innate ability to detect magnetic fields and navigate via subtle changes in the fields around Earth8. Using fluctuations in magnetic fields as “landmarks”, loggerheads traverse the ocean by making specific turns to conserve energy by taking advantage of currents. Once they reach sexual maturity, turtles will mate in coastal waters, and females will travel back to their original nest to start the cycle again.

The average lifespan of a loggerhead is thought to be around 50 years in the wild, however there are many threats to their survival. All sea turtle populations are in decline mainly due to unregulated fishing, pollution, and destruction of habitat. Loggerhead turtles have been listed as threatened since 19781. There are many conservation efforts underway to encourage growth in their populations, but there are also some things that you can do personally9:

  • Use a red flashlight if you are out on the beach at night to avoid disturbing nesting turtles
  • Stay away from known nesting sites
  • Make sure plastic trash gets thrown away properly, so it doesn’t end up in the ocean
  • Keep all dogs on a leash
  • If you’re on the beach, make sure outdoor lights and any motion sensors are turned off at night during nesting season

If you want to see a live sea turtle, you can visit the North Carolina Aquarium at Fort Fisher or the Karen Beasley Sea Turtle Rescue and Rehabilitation Center.




Previous Columns

July: Plastic Free July
June: All About Alligators

Loggerhead hatchlings trek toward the ocean
Image credit: Paul F. Boniface
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