A Department of Parks and Wildlife (DPAW) spokesman said 135 captive-bred young western swamp tortoises had been released in the Moore River Nature Reserve, including 38 last July.
"The western swamp tortoise is one of the world's most endangered tortoises and is Australia's rarest reptile," he said.
"Formal conservation management under a specific recovery program and establishment of a recovery team for the western swamp tortoise started in 1990.
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READ NOW"The objective of this plan, led by DPAW, is to create at least three wild naturally-recruiting populations, increase the total number of mature individuals in the wild (and) to conduct translocations to additional sites."
The spokesman said there were two known wild populations, in Ellenbrook and Twin Swamps nature reserves, between the 1960s and 2000.
He said DPAW had established transplanted populations at Mogumber and Moore River since 2000, but exact survival rates were unknown.
"Based on monitoring and available information, it is estimated that at least 160 released western swamp tortoises have survived in the wild," he said.
"While there can be a high mortality rate, the survival rate of released captive-bred juveniles is higher than those of wild-born hatchlings."
The spokesman said the tortoise species could live as long as humans, but less than 50 adults were known to exist in the wild.
"One individual has been radio-tracked for 52 years and is believed to be more than 65 years old," he said.
Environment Minister Albert Jacob recently announced funds for a breeding facility at Perth Zoo to care for up to 250 tortoises.
"The new facility includes four big quarantine ponds which will enable the zoo to care for sick or injured tortoises that need to be rescued from the wild," he said.
"The tortoises are big water users and it's one of the reasons they are struggling in our warmer, drier climate.
"On average the zoo's 49 tortoise ponds need 30,000 to 50,000 litres of fresh, clean water a day.
"This new facility has been designed so the water can be re-used across other parts of the zoo, such as on the gardens or even to flush the visitor toilets."
Since 1989, Perth Zoo has bred more than 800 western swamp tortoises and 668 have been released by DPAW to boost numbers in the wild.