Twenty of the world’s most critically endangered reptiles have been released at a site near Moore River, north of Perth, as part of the ongoing conservation effort to boost wild populations of the species.

The 20 western swamp tortoises, aged between two and 13 years and bred and raised at Perth and Adelaide zoos, were fitted with radio transmitters prior to release to help scientists better understand their behaviour following translocation.

The release site is part of the Department of Biodiversity, Conservation and Attractions (DBCA) Western Shield program, which protects vulnerable native wildlife from feral predators.

DBCA Senior Research Scientist Dr Gerald Kuchling said researchers will compare the movement patterns of the freshly released turtles to see how they differ to the movement of turtles already established at the release site.

“We will catch and tag a similar number of turtles of similar age and size from the established population here to learn how the different groups behave and how their behaviour changes as they settle into the environment,” Dr Kuchling said.

“It will also help us learn more about how factors such as age, sex and whether they were born in the wild or at a zoo impact their behaviours.”

DBCA Conservation Officer Nick Rodriguez said the radio trackers’ battery life will last between eight months and a year.

“We will return regularly over the next 12 months to monitor the turtles and check on their growth and movements,” Mr Rodriguez said.

“This site appears to be less vulnerable to the drying trends we are seeing across the Perth region, so it’s good habitat for the western swamp tortoise.”

Perth Zoo Science Program Leader Dr Harriet Mills said Perth Zoo’s western swamp tortoise breeding program had likely made the difference between extinction and survival for the species.

“When we started breeding in the late 1980s, the species was down to the last handful of animals, so without this breeding program it’s likely we would have lost this species,” Dr Mills said.

Most years, DBCA scientists release western swamp tortoise juveniles from Perth Zoo to carefully selected sites north of Perth and in the south-west.

This latest release was supported by the Friends of the Western Swamp Tortoise group, which is an initiative of the Threatened Species Network.

Fast facts:

• Western swamp tortoises (Pseudemydura umbrina) were thought extinct for 100 years before being rediscovered in the Swan Valley in 1953.
• Land clearing and altered drainage destroyed much of the species’ original habitat and associated ecological communities. 
• The Perth Zoo western swamp tortoise breeding program started in 1989 with the first release in 1994. Since then, the program has bred more than 1300 western swamp tortoises of which 1145 have been released into the wild to strengthen existing and new populations.
• Western swamp tortoises have a brown or black shell, a short neck covered with tuberacles (knobbles) and webbed toes with five claws on each foot. They grow to between 11 and 13cm in length and weigh between 300 and 450g.