Sea turtles use sunrise to set their internal compass, researchers say
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Sea turtles may be using the sun to set their internal compasses, new research suggests.
The marine animals have a remarkable ability to find their way home, and the research from James Cook University suggests they make significant directional adjustments at sunrise.
Scientists tagged 22 turtles, dropped them in unknown waters 28 kilometres away and tracked their journey home.
Dr Takahiro Shimada said the turtles use of sunrise to adjust their direction came as a surprise.
"We didn't expect that at all because there's no studies showing their directional correcting in relation to sun," he said.
"But we found something is happening around in the hours around sunrise."
What exactly is happening is still unknown, but Dr Shimada said the research suggested turtles used the sunrise to calibrate their cognitive map and directional information.
"One theory is, obviously the sun comes up from the true east, so they may be using the direction of the sunrise to calibrate their internal compass," he said.
"The other possibility is that they may be using the polarised light, which we see in other animals like birds when the sun is on the horizon.
"So that's something we could look into in further research."
Turtles navigate home from hundreds of kilometres away
Dr Shimada said turtles displayed a striking travel pattern which involved alternating between long travelling and stationary periods.
"The median travelling period of eight hours was followed by a median resting period of close to nine hours," he said.
"The turtles would change direction when the resting period ended, usually early in the morning."
Dr Shimada said previous research has shown turtles can be dropped in unknown waters up to a few hundred kilometres away and always return to their home area.
"There is strong evidence that turtles use geomagnetic and possibly wind or current-borne cues for orientation as well," he said.
But Dr Shimada said the most significant correction to their direction of travel occurred at sunrise.
Topics: environment, environmental-impact, environmental-policy, environment-education, environmental-health, science-and-technology, research, research-organisations, townsville-4810, james-cook-university-townsville-4811, gladstone-4680, qld
