Turtle Tradition

How sea turtles find their nesting sites

As they scuttle across the sand toward the ocean, newborn sea turtles are already creating decades deep memories. They imprint on the chemical specifics of the sand, coast, and ocean. These become a coordinate system of directional cues that, ten to fifteen years later, will guide the mature females back to their birthplace. Just as the tide predictably rolls on and off the shore, the females will return year after year to the same beach to lay their own eggs.

Researchers think the reason why sea turtles do this is to ensure they lay their eggs somewhere with all the nesting necessities—sand type, temperature, accessibility, and low predator presence. They trust the beach their mothers chose for them. How exactly, at ten to fifteen years old and across over 1000 miles, they end up at the same spot they were born is still unclear. Sea turtles are presumed to have magnetic particles in their brains that detect and respond to planetary angles of inclination and declination. By picking up on their birthplace’s unique magnetic features, they seem to create their own compass that points back to their first beach. This magnetic imprinting is repeated generation after generation, making nesting site a sea turtle tradition. Shifts in Earth’s magnetic field occasionally cause sea turtles to miss their target, but, overall, the animals have remarkable accuracy across their entire reproductive decades.

Even people have enlisted sea turtles’ internal compasses for conservation. From 1978 to 1988, after the Kemp’s ridley sea turtle’s nest numbers in Tamaulipas, Mexico, reached unsustainable lows due to human interference, conservationists moved eggs from Mexico to Padre Island, Texas, to provide a new nesting site for the critically endangered species. In 1996, a female Kemp’s ridley, who was relocated and hatched in 1983, returned to Padre Island. Since then, Kemp’s ridley sea turtles have continued to return to the Texas nesting site to lay their eggs. Twenty-five years after the relocation project, Kemp’s ridley worldwide nest counts increased from 702 to 20,000. Since then, oil spills and pollution have taken a toll on the species, but if we continue to conserve the Kemp’s ridley—and all other sea turtles— hopefully, beyond our own lifetimes, sea turtle hatchlings will crawl across the same stretch of shoreline we see their ancestors traveling today.

 

Sources

Emslie, Karen. “How do sea turtles find their way home?” Discover Wildlife, https://www.discoverwildlife.com/animal-facts/reptiles/how-do-sea-turtles-find-their-way-home/

“How Baby Sea Turtles Find Their Way Home.” WETA, https://weta.org/watch/shows/its-okay-be-smart/how-baby-sea-turtles-find-their-way-home

“The Story of the Kemp’s Ridley.” National Park Service, 10 Oct. 2020, https://www.nps.gov/pais/learn/nature/kempsridleystory.htm