Baby turtles don't just go with the flow

EarthSky.org reported on research published in Marine Biology in 2011 by Rebecca Scott, a PhD student at Swansea University’s College of Science, http://earthsky.org/earth/baby-turtles-dont-just-go-with-the-flow. The work has shown how hatchling loggerhead turtles can navigate the Atlantic Ocean’s powerful currents and influence their direction of travel by paddling for a few hours each day and using the Earth’s magnetic field to orient themselves.

Rebecca added “Being further south has clear benefits for the hatchling turtles. It can help them avoid being carried towards northern Europe, where the water is too cold and would kill them, and the warmer water in the south also boosts their metabolism and feeding rate. As long as there is plenty of food, any turtles that reach warmer waters can grow faster than if they were stranded in cooler seas.

Laboratory experiments carried out by other scientists have shown that loggerhead turtle hatchlings change their preferred swimming direction when they are exposed to the Earth's magnetic field present at different locations in the North Atlantic ocean. The Earth's magnetic field changes across the surface of the Earth and the observed directional swimming responses of hatchlings have been proposed to help hatchlings stay within favourable warm watered development habitats. But, until now, there was no evidence that such tiny animals with such weak swimming abilities could actually influence their destiny with a small amount of directional swimming.

The loggerhead turtles that hatch on beaches in Florida immediately take to the oceans. Ocean currents then enable hatchlings to quickly disperse away from predator rich coastal habitats to safer oceanic development habitats, where they will remain for seven or eight years before returning to coastal sub adult development habitats around Florida. They depend on the eastward flowing ocean currents at the northern boundary of the North Atlantic Gyre to cross the Atlantic ocean and reach the Azores, whose warm, food-rich waters provide an ideal environment for the young turtles. The location of the Azores also provides easy access to the westward flowing return leg at the southern boundary of the North Atlantic Gyre, which then helps turtles return to Florida.

The findings that a little swimming can have a big impact on the dispersal of small organisms such as hatchling loggerhead sea turtles, has big implications for a range of other species that also disperse in ocean currents. It will also help conservationists to better understand the dispersal of key species, for example invasive species and species of conservation concern, and therefore better design effective conservation measures.”