Marine turtles shun spotlight

First published 4 December, 2012

James Cook University scientists have been the first to calculate the effect of light pollution on Australian marine turtles.

The findings were part of a project by JCU PhD student Ruth Kamrowski, and were published recently in International Journal Endangered Species Research.

Dr Mark Hamann, the JCU biologist who supervised the research, said light pollution had long been one of the challenges of marine turtle ecology in Australia.

“Under dark skies, hatchling turtles use the horizons to navigate down the beach and offshore,” he said.

“So when exposed to artificial light, hatchling turtles trying to escape to the sea can become disorientated and cause them to wander inland, be confused and possibly swim parallel rather than perpendicular to the coast. This then results in higher mortality,” he said.

Dr Hamann said while even small lights like torches could disorientate hatchlings, the light pollution they studied originated from larger sources such as urban settings, coastal development and industry.

“This finding alters our understanding of the field, to say the least,” Dr Hamann said.

“Although it is well known that turtle hatchlings are disorientated by artificial light, this is the first study to quantify the magnitude of impact.

“The results demonstrate that there are two regions light pollution impacts on marine turtles – the north west shelf of Western Australia and south east Queensland.

“We were amazed at the sheer scale of impact in these two main locations when we made the discovery.”

Dr Hamann said four of the six species of Australian marine turtles were affected across much of their nesting habitat.

“Certain management units appear to face high levels of risk, with 99 percent of hawksbill turtle nesting sites and 87 percent of flatback turtle nesting sites in Western Australia determined to be at risk from light pollution. And of the 10 nesting sites - by species - in Australia at highest risk from light exposure, six occurred in south east Queensland and four in WA.

“The study indicates that rigorous light pollution management is vital, particularly given the importance of the turtle populations which nest here.”

Dr Hamann said a better understanding of the effects of light pollution may help scientists plan more successful strategies for the management of development in and around key habitat for marine turtle populations in the future.

“The research results have important implications for how the Government and developers deal with cumulative light pollution for all the sites a species use, rather than addressing them within development footprints one at a time as is current practice.”

The full details of the findings can be found at http://www.int-res.com/articles/esr_oa/n019p085.pdf

For interviews, contact – Mark Hamann, James Cook University 07 4781 4491 or 0415 298 238 or Ruth Kamrowski on ruth.kamrowski@my.jcu.edu.au or 0488 535 923