Western swamp tortoises released

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Western swamp tortoises bred at the Perth Zoo were released in the Moore River nature reserve in Wanerie this week. Picture: Perth Zoo

THIRTY western swamp tortoises were released in Moore River nature reserve in Wanerie on Tuesday.

The tortoise – one of Australia’s most critically endangered reptiles – came from the Perth Zoo, which since 1989 has bred tortoises so some can be released in the wild.

Department of Biodiversity, Conservation and Attractions senior research scientist Dr Gerald Kuchling and Perth Zoo keeper Bradie Durell took part in the release.

The Parks and Wildlife website said the tortoises are carnivorous and eat only live food such as insect larvae, crustaceans, earthworms and small tadpoles.

“The western swamp tortoise has been found only in transient swamps in a 3-5km narrow strip of the Swan Coastal Plain near Perth,’’ the website said.

“This strip runs parallel with the Darling Scarp extending from Perth Airport to Pearce Royal Australian Air Force Base at Bullsbrook.

“It is thought that the tortoise has always had a restricted distribution, however, this has become even more limited as its preferred habitat along the Swan Coastal Plain was cleared for agriculture, urbanisation and for extraction of clay for brick and tile manufacture.

“The only surviving populations are located at Twin Swamps and Ellen Brook nature reserves which were created to protect the remaining habitat of the tortoises.

“The Western Swamp Tortoise has been translocated to Mogumber Nature Reserve and Moore River National Park.

“Habitat destruction and fox predation have been the major causes of decline.

“Hatchlings must reach a weight of at least 25g in their first six months in order to survive the following summer and often this is not achievable in years of low rainfall as the swamps only retain water for a short time.

“It is also thought that females are unable to produce eggs in low rainfall years.

“Therefore, for recruitment to succeed there must be two successive years of average or above average rainfall.

The numbers of tortoises have undoubtedly been affected by the many years of below average rainfall in Perth since the 1960s.

“Other predators, such as dogs, feral cats and ravens, are also believed to impact upon the survival of the tortoise.’’