Australia's disappearing sea snakes

4 May 2012

A turtleheaded sea snake [Image: Dr Vimoksalehi Lukoschek]
A turtleheaded sea snake [Image: Dr Vimoksalehi Lukoschek]

Australia's sea snakes may be more in danger of extinction than previously thought, marine scientists from the ARC Centre of Excellence for Coral Reef Studies say.

New research by Dr Vimoksalehi Lukoschek from James Cook University with Professor Rick Shine from the University of Sydney, on turtleheaded sea snakes, has found that they are strongly attached to their home reef and rarely venture even a few kilometres to neighbouring reefs.

The turtleheaded sea snakes occur in shallow-water coral reef habitats from the Philippines to the Great Barrier Reef and from New Caledonia to north western Australia.

The researchers used genetic 'fingerprinting' to show that the turtleheaded sea snakes behaviour has resulted in significant genetic differentiation in populations living on adjacent reefs.

The study has been published in the latest issue of Ecology and Evolution.

The researchers found that the genetic divergence confirms that snakes rarely travel to other locations to mate, regardless of the distance. This means that if one population were to decline or disappear, it is unlikely to be 'replenished' by neighbouring snakes, because snakes rarely move between reefs.

"For eight years, sea snakes on two reefs that are adjacent to each other in New Caledonia have been captured, tagged with a microchip device and released," says Professor Rick Shine.

"In almost all instances, the snakes were repeatedly recaptured on the same reef during summers and winters.

"This finding matches with the genetic dataset, which showed that snakes on their home reefs were more closely related to each other genetically, than they were to snakes on the neighbouring reef. Similar genetic patterns have also been documented for other coral reef sea snake species."

The implications are that coral reef sea snakes are extremely vulnerable to disturbances in their local habitats, which could be caused by human activities or environmental changes.

This is of great concern, according to the researchers, given that some Australian populations of turtleheaded and other reef-associated sea snakes have undergone massive declines or local extinctions in recent years, particularly at Ashmore Reef in the Timor Sea, and also on some reefs in the southern Great Barrier Reef.

While the reasons for this behaviour of sea snakes are still unknown, physical barrier is not one of them, the researchers say.

The findings raise doubts on the ability of Australia's coral reef sea snake populations to recover from serious setbacks and highlight the need for greater awareness about the conservation status of these species.

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