Sunday, 22 May 2016

Ningaloo turtles struggle with bright lights

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The researchers glued the smallest acoustic transmitters available onto 40 baby sea turtles so they could follow the 5cm hatchlings without affecting their swimming ability. The researchers glued the smallest acoustic transmitters available onto 40 baby sea turtles so they could follow the 5cm hatchlings without affecting their swimming ability. Image: U.S. Fish and Wildlife Service Southeast Region
  • 90 per cent of turtle hatchlings became disoriented from artificial lights
  • Failing to reach deep waters means the turtles are less likely to survive
  • Researchers suggest using a spectrum of lights that won’t attract turtles

BABY turtles born on a WA beach are having trouble navigating into deep water because of artificial lights such as those from ships and offshore resource projects.

study of green turtles (Chelonia mydas) near Ningaloo Reef has discovered 90 per cent of turtle hatchlings swam towards an artificial light and became disoriented during their journey out to sea.

UWA oceanographer Charitha Pattiaratchi says turtles lay their eggs on the beach and the hatchlings emerge at night.

“They navigate themselves, basically, by the Moon to make sure that they go offshore,” he says.

“If you have artificial light, what we’ve shown is that they actually don’t go out to sea, they get attracted to the light.

“So if you’ve got a ship or a drill point or a drill rig, they change their path.”

The researchers glued the smallest acoustic transmitters available onto 40 baby sea turtles so they could follow the 5cm hatchlings without affecting their swimming ability.

Half the turtles were subjected to artificial light and the scientists tracked where they swam using an array of acoustic receivers.

They also measured ocean currents at the time of the turtles’ release.

A sea turtle hatchling. Credit: Joan Costa.

 

“We had to take the currents out of the equation so that we know that they actually get attracted because of the light and not because they get swept by the currents,” Prof Pattiaratchi says.

While previous studies have shown baby turtles are attracted by lights on land, the research—published in Royal Society Open Science on Wednesday—claims to be the first experimental evidence that wild turtle hatchlings are attracted to artificial light after entering the ocean.

Prof Pattiaratchi says the hatchlings’ survival is compromised if they fail to navigate offshore.

“They get more predators and they get disoriented, so the success rate of them becoming an adult diminishes quite a lot,” he says.

But there are ways to reduce turtle hatchlings’ exposure to artificial light.

“[We could] find different ways of lighting, a different spectrum and also shade them so they’re less visible to turtles,” Prof Pattiaratchi says.

A 2005 study of turtles nesting on Barrow Island, the Lowendal Islands and the Montebello Islands found sea turtle hatchlings are able to see both ultraviolet and visible light.

It suggested the threat to hatchlings from artificial light depends on its brightness and wavelength, with turtles responding most strongly to blue and green light.

Turtle hatchlings were also more attracted to artificial lights when there was less moonlight.

Notes:

The research carried out by the Australian Institute of Marine Science, UWA and the Department of Parks and Wildlife.

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