Earth's Magnetic Field Helps Turtles
This is the VOA Special English ENVIRONMENT REPORT.
American scientists have found strong evidence that baby sea turtles are born with the ability to recognize and measure Earth's magnetic fields. They found that the sea turtles use the magnetic fields to guide them as they swim great distances across the ocean.
Scientists at the University of North Carolina at Chapel Hill did the research. Science magazine reported the findings.
The scientists say the baby sea turtle is one of the great wonders of the animal world. Baby turtles swim directly to the open sea shortly after breaking out of their eggs. The young turtles follow complex paths that often lead across large areas of seemingly endless ocean. Baby sea turtles swim across the Atlantic Ocean and back all by themselves. People have wondered for years how they do this.
The longest and most surprising trips are made by young loggerhead turtles. Young loggerheads in the North Atlantic Ocean swim more than fifteen-thousand kilometers across the ocean before returning to the North American coast.
Loggerheads in the state of Florida follow a huge, circular current of warm water known as the North Atlantic gyre. The gyre moves from the East Coast of the United States across the North Atlantic and then south along the coasts of Spain and Africa before turning west to complete the circle. Water in the gyre is generally warm and food there is plentiful. Turtles that leave the gyre often die from the cold water.
The scientists wanted to find out if baby loggerhead turtles could recognize the magnetic fields in different parts of the North Atlantic gyre. They used turtles that had never been at sea before. They placed the turtles in a container filled with saltwater. They put wires around the container. The wires produced magnetic fields similar to those found in different parts of the gyre.
Whenever the turtles were in a magnetic field like that found in the ocean, they swam in a direction that would keep them in the warm current.
One of the scientists, Kenneth Lohmann, says the findings provide direct evidence that turtles can use Earth's magnetic fields as markers. He says similar systems might exist in other ocean creatures and even some birds.
This VOA Special English ENVIRONMENT REPORT was written by George Grow.