Turtles swim across an ocean – and back
THE first little turtle did a loop around Lord Howe Island before heading east towards New Zealand.
The second one sped down the Australian coastline, riding the Pacific Ocean’s superfast highway – the East Australian Current, just like the turtles in the movie Finding Nemo.
The journey of these little ‘‘dudes’’ is a rare insight into the life of the mysterious, and endangered, Australian loggerhead turtle.
‘‘Nothing is known about the Australian loggerhead,’’ says Libby Hall, the manager of the wildlife hospital at Taronga Zoo.
After leaving their nesting beaches, hatchlings are rarely seen until the females of their clutch return to lay eggs on the same shores three decades later.
To build a travelogue of these creatures, Hall has teamed with international biologists to satellite track several turtles during these ‘‘lost years’’.
The team hopes the tracking data will eventually be used to alter commercial fishing routes and reduce the number of turtles killed as bycatch, a major cause of their dwindling population.
A young turtle being tracked, named George, who was released at Lord Howe Island in January, had travelled down the Australian coastline via the EAC and was now somewhere south of Sydney.
‘‘We don’t really know where it is going,’’ Ms Hall said.
‘‘Each time it surfaces that’s when [the tracker] connects to the satellite.’’
While it was probably using the EAC for a free ride, the area where the current’s warm waters converged with the surrounding cooler water was an important turtle feeding ground, she said.
‘‘They swim along with the currents, but they’re not just being swept along,’’ Ms Hall said.
The first turtle the team tracked in 2010 swam a different route, taking 221 days to circle Lord Howe Island before heading to New Zealand where its tracking device stopped relaying data.
‘‘The devices stay on for a bit over a year. They shed as the animal grows,’’ said Ms Hall, who hoped the program would track more turtles.
The researchers, including a biologist from the Pacific Island Fisheries Science Centre in Hawaii, George Balazs, and one of the zoo’s vets, Kimberly Vinette Herrin, have some clues about where the turtles may go.
In 2009, Queensland geneticists found loggerheads swimming in waters off the coast of South America had the same genetic background as Australian loggerheads, who can live to 50 years of age.
While female loggerheads were sexually mature from six years of age, they generally returned to nest on Queensland’s beaches when they were 25 to 30 years old.