Tuesday, January 31, 2023

After study shows sea turtles navigate using magnetic fields, group moves away from metal

BHI Conservancy has been protecting sea turtles eggs from predators for a while. But a new study has them changing their tactics.

Bald Head Island Conservancy has avoided using metal cages in its sea turtle conservation efforts to avoid any potential harm. New research reveals sea turtles rely on magnetic fields to navigate. (Port City Daily /FILE PHOTO)

BALD HEAD ISLAND—New research has helped shape how local conservationists handle sea turtles.

Every few years, the same sea turtles will return to the same beaches. How?

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According to a recent study produced by UNC-Chapel Hill researchers, the reptiles of the ocean rely on the magnetic field of the earth to find their way back home.

It found that sea turtles exhibit a behavior called “geomagnetic imprinting” to seek out “unique magnetic signatures along the coast.” This leads them to return to their natal beaches to reproduce, which ultimately shapes the species’ population structure.

Metal to plastic

On Bald Head Island, researchers have already incorporated information shared in the process of releasing the UNC-Chapel Hill study.

So as to not interfere with the turtle’s magnetic sensory systems, BHI Conservancy pre-emptively incorporated plastic cages over metal cages in its efforts to protect nests. 

Bald Head Island Conservancy’s sea turtle coordinator, Natalie Monnier, said the transition started last summer.

“Because of what they were working on and because of their findings we thought it would be best to transition to plastic,” Monnier said. 

New research has lead the team to avoid metal cages in case they are harmful to the hatchlings.

“We started last summer using plastic cages along with our metal cages,” Monnier said. “Before, we were just using metal.”

Through its conservation efforts, the BHI Conservancy has a network of tagged sea turtles that it monitors throughout the years. The group is able to monitor when a female sea turtle is preparing to lay her nest.

A cage — now plastic — is installed about a foot deep. It protects the eggs from foxes, raccoons, coyotes and most other predators.

“The cages have big enough holes that the hatchlings are able to get out on their own,” Monnier said.

Monnier said last summer, the group sent over a couple hatchlings from the newly adopted plastic cages to UNC-Chapel Hill’s Lohmann Lab for researchers to study.

As for the turtles that return to the region’s beaches, Monnier said BHI Conservancy has identified several “legacy turtles.”

Though turtles nest every two to three years, the group has still seen the same turtles return to lay their eggs.

 “We’re seeing that pattern in them coming back,” Monnier said. “Some turtles have been coming for 15 years now.That’s really good for us because our beaches are good enough for them to keep coming back.”

After analyzing years of data gained from tagging sea turtles, Monnier said the group has seen an increase of nests on Bald Head Island. 

Johanna Ferebee can be reached at johanna@localvoicemedia.com or @j__ferebee on Twitter

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