The mysterious Cooper Creek turtles

Scientists are continuing their 20 year survey of one of Australia’s most unique turtles which lives in waterholes in the arid zones of western Queensland and north east South Australia.

The Cooper Creek Turtle, also known as Emmotts Turtle, is one of Australia’s largest freshwater turtles and can grow to more than 7.5kg.

Scientists last year camped at Noonbah Station, 160km south-west of Longreach, to collect and tag turtles using nets. The animals were often covered in algae; and exhibited megacephaly – enlarged head sizes – across all ages and sexes, although the researchers say it was “particularly pronounced in adult females”.

Teams from the University of New England and Canberra University have been visiting the region for more than 20 years, camping alongside Waterloo, Fishhole and Broadwater waterholes in one of Australia’s most inhospitable climates. Their latest report was published in Austral Ecology.

The researchers say they are scratching the surface of what they know of the turtles. 

The Cooper Creek Turtle (Emydura macquarii emmotti – E. m. emmotti) lives in the border region of Queensland and South Australia.

The Creek experiences dynamic and unpredictable boom–bust systems: “… that oscillates between periods of bountiful nutrients and periods of extremely limited resource,” the researchers wrote.

Donald McKnight is a biologist who led the research into this rarely surveyed turtle with Deborah Bower, Arthur Georges, and Fiorenzo Guarino.

He says the climate change impact on the Cooper Creek Turtle could be devastating.

“Climate change may end up being really detrimental to the system, especially if you get higher droughts happening. Longer and more severe droughts mean that these waterholes may start going dry more frequently,” McKnight says.

The turtles’ megacephaly was surprising.

“Megacephaly in Latin…literally means big head, ‘mega’ big and ‘cephaly’ head,” says McKnight.

“Usually in turtles, and in a lot of animals, when you get megacephaly, it has to do with what they’re eating.” Females dont eat the same diet as males.

There are other size differences between males and females. Females are larger and males have a longer tail.

Size difference depending on sex/age. Credit: Austral Ecology

With an maximum recorded size of 402 mm (straight-line carapace length) and estimated mass of  over 8 kg, E. m. emmotti is one of Australia’s largest chelid turtles by weight.

”Chelidae” is a family of aquatic or semi-aquatic freshwater turtles. Chelids have distinct ankle joints and webbed feet with four or five claws, and other niche features.

McKnight hopes to continue studying the Cooper Creek Turtle.

“The hope is to really make this a long-term project we [can] go back year after year,  and look at growth rates and individuals as well as the population dynamics itself, and then see if we can correlate good years for turtles with what’s happening with the water cycle.”

It took the team 2 days’ driving to get to Cooper Creek, where they camped for 10 days.

“It could look lifeless at a quick glance, but then you get around these waterholes. They’re full of fish and turtles and birds and kangaroos and dingoes and everything else are coming to [the waterholes].

“We still aren’t sure how far individuals migrate (at least 15 km), but the species is found along nearly the entire length of Cooper Creek (all the way down into South Australia). So Burke and Wills certainly could have encountered (and possibly eaten) them.”

The research hasn’t come without challenges. One year, they went during the dry season, but it didn’t go to plan due to an unexpected downpour.

“We were camped next to the waterhole, and were out watching as the water levels kept rising up and up and up around the campsite.”

The problem with the wet earth in the desert is it is incredibly sticky.

“You try to walk [and] you get kilograms of mud stuck to your feet.”

Bower brought her dog. It was having a miserable time with mud.

“[The] universities weren’t thrilled with us being stuck out there in those conditions, but not much you can do about it once it’s happened.”