Native turtles under threat in Perth's Hyde Park, infants missing - via Herp Digest

By Gian De Poloni,  ABS.New.au  May 5, 2017, 9:08pm

A native species of turtles living in one of Perth's most popular lakes is in danger of dying out.

Researchers believe not one juvenile has joined the colony of oblong turtles living at the two lakes in Hyde Park in more than a decade and it is unclear why.

A University of Western Australia study into the health of the 300-odd turtles living at the park was triggered in 2015 after anecdotal reports of a drop in the number of sightings.

Roberta Bencini, an associate professor at UWA's School of Agriculture and Environment, said it was an unusual phenomenon.

"That's very strange, it's like going into a city and seeing only old people — you don't see any babies, you don't see any children, you don't see any teenagers," she said.

Ultrasounds conducted on female turtles caught during the study show they were indeed breeding and carrying eggs.

But for some reason, the young are not surviving.

Cannibalism of infant turtles ruled out

UWA graduate Blaine Hodgson was one of the lead researchers in the study and said predators were most likely to blame.

"Between the nests being laid and the hatchling turtles moving into the lake, we are losing the turtles," he said.

"Either the eggs are being predated on once they're buried or they're hatching and being predated on.”

While foxes have been known to prey on the nests of the oblong turtles in rural areas, Mr Hodgson said it was unlikely they were to blame at Hyde Park.

"During trapping we captured a short-finned eel which may have been released by a member of the public some years ago," he said.

"As an opportunistic carnivore, it is quite possible that it was preying on hatchling turtles.”

Mr Hodgson ruled out any suggestion the carnivorous turtles were resorting to cannibalism.

"There are no signs [of that] however it's possible that the older, larger turtles are outcompeting the young ones for resources," he said.

Hatchlings may be in suburban backyards

Mr Hodgson also said the turtles were nesting anywhere up to a kilometre away from the park, making themselves vulnerable to domestic pets and vehicles.

Hodgson said more studies were needed to determine exactly what was happening.

"One possible method to figure out what is predating on these turtles is to use artificial nets and camera traps," he said.

"We plan to radio-track females that are just about to lay their eggs and see what the preferred nesting sites are, whether it's the islands in the middle of the lake, the park land surrounding the water or if they're leaving the park altogether and nesting in people's backyards."

The City of Vincent has flagged financial support for further studies to find out what can be done to improve the turtles' chances of surviving.