Turtle tracks tell a story

On a hot September day, the propeller of a six-seater plane shudders to a stop on a tiny flat, treeless island. From the air, hundreds of resident juvenile green turtles were spotted feeding along the surrounding reef.

Troughton Island or Wudaibiri in Wunambal Gaambera language, is about 80 km from Kalumburu, off the north Western Australian coast on Wunambal Gaambera Country.

Desmond Williams, Senior Uunguu Ranger, jokes, “Sometimes crocodiles try to board the planes here.” During the wet season the area around the airstrip becomes an oasis for thousands of shorebirds – or a potential feast for local crocodiles. Desmond continues to care for Country as his ancestors have for tens of thousands of years.

“Turtles (mangguru) are a key priority in the Wunambal Gaambera Healthy Country Plan due to their cultural significance. Six species of turtles are found in these waters and four of those nest here,” explains Dr Tom Vigilante, Wunambal Gaambera Healthy Country Manager, employed by Bush Heritage.

“It’s a significant area for turtle conservation, but there isn’t enough scientific data to understand the population, nesting locations and the impacts of climate change.”

To help overcome this challenge, Wunambal Gaambera received an Australian Government grant through the Marine Turtle Climate Change Resilience and Nest Protection Program. The project involves deploying sand temperature loggers to track nest temperatures and the analysis of aerial imagery taken during the peak of summer and winter nesting seasons across their saltwater Country.

“Climate change is causing feminisation of some turtle populations. Turtles have temperature dependent sex determination. At 29 degrees Celsius there is a one-to-one ratio of male and female hatchlings in the nest. Warmer temperatures produce more females, while cooler temperatures produce male – ‘hot chicks’ and ‘cool dudes’,” explains Dr Melissa Staines, a turtle biologist working with Wunambal Gaambera Aboriginal Corporation (WGAC).

Climate change can also increase rates of hatchling mortality and impact food sources like coral, algae and sea grasses. As sea levels rise, there will be less nesting habitat available to turtles.

The Kimberley has experienced a record-breaking heatwave this past winter, and the sun’s power is felt by the team walking the beach looking for tracks and signs of nesting.

“You need trained eyes to differentiate hatchling tracks from crab tracks. And to see the difference between the butterfly-style parallel marks of a Green or Flatback Turtle, and the freestyle alternating marks of a Hawkbill or Olive Ridley Turtle.”

Prior to the island trip, WGAC’s Uunguu Ranger team honed their tracking skills – from a digital bird’s eye perspective. They scanned through hundreds of high-resolution aerial images of the region’s beaches and logged data, including signs of nesting or false crawls – when a nesting mission is aborted – as well as evidence of predators. The data analysis will continue, covering thousands of kilometres of the Uunguu Coast. Every beach, every cove, is another opportunity to better understand and protect the turtle population. •

We gratefully acknowledge Wunambal Gaambera Aboriginal Corporation for their partnership and Wunambal Gaambera Traditional Owners for welcoming us to their Country.