Wild sea turtle hatchlings are confused by artificial light

Michele Thums

Baby sea turtle hatchlings are born with an instinct to follow the light. When they first emerge from their nest they use natural light sources around them, such as the Moon, to help guide them to the ocean.
However with more and more light pollution finding its way into our skies and near our beaches, baby sea turtles are finding it more difficult to get where they need to go. Artificial light can lead baby sea turtle astray and will even follow it in the opposite direction of the ocean.
“It is widely known that artificial lighting near turtle nesting beaches attracts turtle hatchlings as they emerge from nests and can cause them to have trouble finding the sea,” Professor Pattiaratchi said.
“But understanding what happens once they reach the sea and how lights on water from sources such as boats, ports and wharves affect them has been unknown up until now because we lacked a simple means to track them.”

A loggerhead hatchling heads toward hotel lights in Florida | Credit: Sea Turtle Conservancy

The theory was tested in a recent study conducted by a collaboration between the University of Western Australia, the Australian Institute of Marine Science, and the Department of Parks and Wildlife, and the findings were published in the journal Royal Society Open Science.
Green turtle (Chelonia mydas) hatchlings were tagged with miniature acoustic transmitters and their movements tracked within an underwater array of 36 acoustic receivers placed in the near shore zone. A total of 40 hatchlings were tracked, 20 of which were subjected to artificial light during their transit of the array.
The team monitored current speed and direction while also tracking the movements of the tiny turtles.. The found that 88% of the turtles followed the artificial light and spent up to 23% more time in the tracking array that turtle under ambient conditions. They also found that currents speed had little to no effect on the direction the hatchling took when artificial light was present.
The findings show that hatched sea turtles are getting confused between the light they need to be following to get to the safest place possible, and the light that could be leading them to further danger. So remember next time you are on the beach at night for the magical appearance of baby turtle, leave the flashlight at home!