Environment Minister James Griffin says 13 of the rare native mice have been released in a national park southwest of Sydney, marking a significant milestone in the recovery of the species from the brink of extinction.
"To the untrained eye, these tiny mice might look quite common, but there are fewer than 100 smoky mice left in the South East Forest, which is one of only two known populations in NSW," Mr Griffin said in a statement on Tuesday.
"This is the culmination of years of painstaking conservation work, which is helping turn back the tide on extinctions and secure this species' survival."
Smoky mice help keep forests healthy by aerating soil, increasing water penetration and spreading truffle spores.
It is one of many species earmarked for rewilding in seven feral-free areas in South East Forest National Park.
The reintroduced smoky mice were bred for conservation by Priam Psittaculture Centre, Research & Breeding, working with Australia's National Threatened Species Institute near Canberra.
The NSW government's Saving our Species Program senior threatened species officer Linda Broome said the trial reintroduction was a major step in the six-year project.
"With such low population numbers in the wild, our long-term goal when setting up the breeding facility was to eventually return this species to its wild, natural habitat," Dr Broome said.
"We are hopeful that the smoky mouse continues to survive in the wild and possibly even increase their population numbers in their coastal forest habitats."
Remote cameras and micro-chip readers have been installed in the national park to provide data on how the mice are faring.
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