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News: Night observations shed light on turtle nesting at Gnaraloo

A team of scientists have collected nine years of data on the nesting numbers and behaviour of the endangered loggerhead turtle on the WA Ningaloo Coast World Heritage Area.

From 2008/09 to 2016/17, Gnaraloo Turtle Conservation Program scientists have undertaken day and night surveys at the Gnaraloo Bay and Gnaraloo Cape Farquhar rookeries located in a 65km stretch of coastline on the southern end of Ningaloo Reef—to record the numbers and nesting behavior of the turtles and the threats to them.

It was estimated that approximately 405 nests are dug by 85 female loggerhead turtles in the Gnaraloo Bay survey area annually. Similar levels of activity were reported in the Gnaraloo Cape Farquhar survey area north of Gnaraloo Bay.

The work took place as part of the Gnaraloo Turtle Conservation Program, which is funded by the Gnaraloo Station Trust and the Australian Government’s National Landcare Programme. Rangelands NRM supported this work up until June 2015, and continues to help support feral animal control at Gnaraloo.

The researchers found that track examinations may result in accuracy errors, as during the day, due to the windswept nature of the area, many of the track features would deteriorate, making it easy to misclassify a nesting activity.

The nocturnal surveys, which involved turtle sightings, directly identified the turtle species and nesting activity which was then used to ensure the accuracy of the track data from the day surveys.

Rangelands NRM Program Manager (Southern Rangelands) Kieran Massie said Rangelands NRM said the predation of turtle eggs and hatchlings by European red foxes, feral cats and wild dogs has been a problem for decades at Gnaraloo, affecting the sea turtle survival.

Project manager Karen Hattingh said one of the Gnaraloo feral animal control project’s great successes this season was another year of zero feral animal interference with the turtle nests, for the seventh year running.

“In 2008, we had 100 per cent of turtle nests taken by foxes in parts of the Gnaraloo Bay Rookery. from the 2010-11 season to now, we’ve had zero disturbance or predation by feral animals of the turtle nests,” she said.

“Foxes don’t know how to dig; they’re taught. So as soon as you eliminate the older population they lose that. They may smell something, but they don’t know how to get it. So the project targeted individual animals who could teach the younger ones.”

The southern extreme of the Ningaloo Coast contains significant and previously unrepresented nesting aggregations of the loggerhead turtle. Despite relatively low nesting numbers, the GTCP researchers said small and isolated sea turtle rookeries such as those at Gnaraloo Bay may still play an influential role in the dynamics of populations and, therefore, have high conservation value.

“Monitoring, research and protection of the Gnaraloo nesting beaches is critical for the successful conservation of sea turtles,” Mr Massie said.

Notes

Original research paper: Thomson Jordan A., Hajnoczky Nora, Hattingh Karen (2016) ‘The Sea Turtle Rookery at Gnaraloo Bay, Western Australia: Using Nocturnal Observations to Validate Diurnal Track Interpretations’, Chelonian Conservation and Biology. 2016 15(2). p.187. [http://www.bioone.org/doi/abs/10.2744/CCB-1219.1]