Turtle Migration Influences by Drift Experiences as Hatchlings

New research has found that adult sea turtles determine where they migrate to and which feeding sites they inhabit is influenced by their drift experiences along ocean currents as little hatchlings.

When they breed, adult sea turtles return to the beach where they were born. And after breeding, they typically migrate hundreds to thousands of miles to their feeding habitats. But scientists never knew what it was that would drive them to migrate to certain spots.

Some adult sea turtles migrate far and wide to find feedings sites, while others don't migrate at all or feed in the open ocean.

Researchers from the University of Southampton looked at what habitats the turtles would have experienced as young hatchlings to get to find out.

They relied on what ocean currents the new-born turtles drifted on once they emerged from their shells and made their way to the open ocean.

By comparing tracking data on adult turtles with models of how the world's sea water moves past nesting sites, the team found that adult sea turtle migrations and foraging habitat selections were based on their past experiences drifting with ocean currents.

"Hatchlings' swimming abilities are pretty weak, and so they are largely at the mercy of the currents. If they drift to a good site, they seem to imprint on this location, and then later actively go there as an adult; and because they're bigger and stronger they can swim there directly," lead investigator Dr. Rebecca Scott explained in a statement.

"Conversely, if the hatchlings don't drift to sites that are suitable for adult feeding, you see that reflected in the behavior of the adults, which either do not migrate or they feed in the open ocean, which is not the normal strategy for most turtle species."

Some juvenile whales and birds learn migration routes by following their mothers or more experienced group members, whilst other bird and insect species are born with the information or a map sense that informs them where they should migrate - but not the turtle. Once a young turtle is hatched, it's on its own.

The findings were published in the journal Ecology.