How animals navigate across the ocean to isolated targets has perplexed researchers for more than 150 years, but new research is unravelling the secrets of the endangered hawksbill turtle.
A team of international scientists, including Deakin University marine biologist Professor Graeme Hays, found that the critically endangered hawksbill turtle may swim in circles, often travelling large unnecessary distances, before finding islands and sandbars. This suggests the species may have a poor sense of direction in the open ocean.
“Those turtles that we’re tracking – they most probably hadn’t eaten for four or five months,” Prof Hays told the Guardian.
Previous research has shown that turtles used the earth’s magnetic field to navigate, but now scientists say the turtles usages may be”incredibly limited”, finding one turtle travelling more than 1300km to find an island just 176km away.
Prof Hays said the turtles are using a “geomagnetic map”, but that this doesn’t pinpoint a straight course to their birth area. Turtles return to where they were born to lay their eggs.
It is thought Hawksbill turtles nest every two to four years, laying between one and six clutches of eggs each time with Hawksbill turtles critically endangered and fewer than 8000 nesting females left worldwide.
Founder of the Rosemary Island turtle tagging program and Department of Parks and Wildlife researcher Dr Robert Prince says turtles do have a sense of direction, but don’t travel point-to-point when in the open water.
“When they’re in the ocean, they’re living their own lives, feeding, living on mainly hard reefs where people don’t trawl,” Dr Prince said.
Dr Price has been marking and tracking turtles off the WA coast since the mid-1980s.
The Rosemary Island turtle tagging program is the longest-running of its kind in WA and Dr Price says he has observed mature breeding female turtles return to the same beaches season after season, since 1986.
Rosemary Island and the Dampier Archipelago support a significant breeding population of hawksbill turtles Each October, volunteers spend two weeks recording nesting activities across five beaches in the area.
The public can track the Rosemary Island Hawksbill turtles here.
The hawksbill turtle are threatened by climate change, poaching, marine debris, coastal erosion and being accidentally caught in fishing nets and on fishing lines.