Do sea turtles use maps?
By Brianna Forte
When a nest of baby sea turtles hatches, it may seem like a magical event. With nests of more than a hundred eggs, the magnificent little creatures all hatch and crawl over each in an attempt to reach the safety of the sea. Although the ability of these tiny turtles to reach the ocean and their knowledge of where to go may seem like magic, there is a scientific explanation.
According to the National Oceanic and Atmospheric Administration, when baby sea turtles hatch they are able to find their way to the ocean based on the slope of the sand and the reflection of the moon on the water. The downward slope of the sand along the shore indicates the direction of the ocean. In addition to the declining slope, the light of the moon reflecting on the water creates the brightest source of light. The reflection almost functions as a giant, neon “Enter Here” sign for the baby sea turtles.
When humans introduce other bright light sources such as streetlights, cars, or beachfront lighting near sea turtle nesting sites, we’re inhibiting the baby sea turtles’ sense of direction. According to SeeTurtles.org, this process is called disorientation and could lead the hatchlings to crawl in the wrong direction away from the water.
Even though baby sea turtles can get confused because of light pollution, they are still expert navigators. In a study based on genetic data conducted by Kenneth Lohman and J. Roger Brothers in 2018, evidence was gathered to support the theory that baby sea turtles imprint on the geomagnetic signature of the beach where they hatched.
According to the National Aeronautics and Space Administration, the magnetic field of earth is caused by the electrical current within the earth’s molten core. Each place on earth has a unique magnetic signature, and baby sea turtles memorize the distinct magnetic field of the beach where they hatch. When these sea turtles reach maturity and are ready to pass on their genes, they return to the same beach to mate and lay their eggs. According to the Sea Turtle Conservancy, most females return to the same beach each year to nest, and sometimes nest within a hundred yards of where they previously nested.
In addition to using geomagnetic imprinting to find where they are going to nest, sea turtles use the earth’s magnetic field for navigation and seasonal migration. Sea turtles are known to have a magnetic compass sense that helps them navigate the open ocean. In another study conducted by Kenneth Lohman and Larisa Avens in 2004, it was found that both juvenile and adult green sea turtles and loggerhead sea turtles use their magnetic compass sense to home to specific locations and aid in seasonal migration.
In this study it was found that when sea turtles were captured during the summer months, the sea turtles returned to their “home” capture site after being displaced 30-167 kilometers. This displayed that both juvenile and adult sea turtles have the ability to determine their homeward direction using magnetic fields. In this study, it was also found that when sea turtles were captured during autumn, the sea turtles oriented themselves southward as soon as they were released. Their orientation coincides with the sea turtle migration behavior of swimming south toward warmer waters in autumn. This study provides evidence that juvenile and adult sea turtles use magnetic fields to navigate and home in on locations, as well as for seasonal migratory orientation.
Although sea turtles are majestic creatures that may seem magical, their immaculate sense of direction is actually developed through navigating the Earth’s magnetic fields!