Hyde Park oblong turtles study launched over fears of dwindling numbers
The first-ever study of native oblong turtles living in one of Perth’s most popular parks is underway to find out why the population appears to be declining.
Spotting turtles in the Hyde Park lakes has been a popular picnic activity for decades, but in recent years the number of sightings, particularly of juveniles, has dropped.
Concerned about the health of the turtles, the Claisebrook Catchment Group lobbied the City of Vincent for a study by the University of Western Australia (UWA).
The initial findings from researchers suggest increased predators and people may be to blame.
By using ultrasounds we can see if they have eggs or follicles. If we can find that out then we can rule out other reproduction problems in the population.Roberta Bencini
Volunteer Dudley Maier said the group did not want to rely on citizen observations about turtles if the population was diminishing.
« Future decisions need to be based on real, hard science, not just the observations from a few people. There are some good citizen science programs but this study is going to be a good base, » he said.
« So in five years’ time, 10 years’ time, we can say the population is stable or increasing or it’s decreasing, and if it is decreasing try and work out is it water quality, habitats or predators? »
The Hyde Park turtles lived in swamps at the same location before the park was constructed in the 1890s, but a census has never been done.
In the last month, researchers from UWA have assessed and microchipped more than 20 of the oblong turtles so they can be tracked for future reference.
The females have also had ultrasound scans by the lake side to check fertility.
Hatchlings may not be surviving, research suggests
University of Western Australia associate professor Roberta Bencini said the team had found several adult females carrying eggs.
« By using ultrasounds we can see if they have eggs or follicles. If we can find that out then we can rule out other reproduction problems in the population, » she said.
« We’ve found females with fully calcified eggs, indicating that she’s probably going to nest in the next few days. »
However in the initial two rounds of trapping, researchers have only found older adult turtles, and that the females are healthily reproducing.
The findings suggest hatchlings are not surviving and thus continuing the population.
Experts said most females sought higher ground to lay their eggs, wandering hundreds of metres to the perimeter of the park and sometimes even into neighbouring yards.
That left the juveniles with a long journey back to the lake, across open park lawns, and left them vulnerable to an increasing number of predators like swamp birds.
Researchers said the lake’s growing swamp vegetation, designed to support the turtle population, may have attracted more birds likely to eat the baby turtles.
There were also concerns people were moving adult turtles back from the outer park to the lake just before they lay, with the disturbance harming the laying process.
It is hoped the nine-month study will help map the population and produce strategies to protect the turtles.