NATIVE animals which haven't been seen in the Pilliga forest for over a century are slowly but surely being reintroduced to their ancestral habitats.

The Pilliga forest is one of multiple NSW national parks which are part of a state-wide biodiversity project in partnership with the state government and multiple wildlife organisations, including the Australian Wildlife Conservancy (AWC).

AWC Regional Ecologist Dr Greg Holland said the project first began a few years ago with the intent of creating safe refuges for endangered mammals.

"One of the main things we've been doing has been the construction of a large feral-proof fenced area of about 5800 hectares," Dr Holland said.

"Then, within that area, we have worked to eradicate all feral introduced species, like cats, foxes, goats and pigs.

"We've used a wide range of approaches, including baiting, trapping and bringing in external contractors with specially-trained dogs."

The AWC has been contracted by the NSW government to manage 36,000 hectares of the Pilliga, with the fenced section being only a small part of that area and other responsibilities including weed control maintaining local assets and ecological monitoring.

According to Dr Holland, ongoing eradication efforts have been very successful, with only a single fox remaining in the wider fenced area.

He said inside this area is an even smaller 680 hectare space now fully eradicated all feral predators where they have been able to start reintroducing extinct species since 2018.

"We've been able to reintroduce two of Australia's most threatened native small mammals - the greater bilby and bridled nailtail wallaby - which used to be common but have been extinct in NSW for over 100 years," he said.

"The bilby was the first to be reintroduced, which happened in late 2018, while the wallabies were slowly reintroduced in August 2019."

The AWC have conducted extensive monitoring of the population growth of both species, with NSW Environment Minister James Griffin paying a visit to the Pilliga earlier this week to see their progress.

ABOVE: NSW Environment Minister James Griffin releases a Bilby with Australian Wildlife Conservancy Field Ecologist Sabrina Carter. Image courtesy of AWC.

Minister Griffin said the partnership between the government and organisations like the AWC - a first for the two - was giving locally extinct animals a second chance.

"I can’t overstate how important this project is for protecting biodiversity – it’s one of the most ambitious mammal rewilding programs in Australia,” Minister Griffin said.

“Here at the Pilliga, we’ve seen the endangered bridled nailtail wallaby population double since it was reintroduced to this now feral-free area in August 2019, from 42 to about 90 at the latest estimate, including many females with joeys in pouches.

“This number is expected to eventually grow to more than 2,000.”

As for the bilbies, Dr Holland said their population growth had seen a similar increase which the AWC was really pleased with.

"We originally introduced 60 individuals and have been monitoring them very closely - our last tracking was in December 2021 and the population estimate was 155," he said.

"This is pretty much in line with our expectations - you never really know how they'll go in rates of increase but we're happy with how they're tracking."

Looking into the future, Dr Holland said he was looking forward to expanding the feral-free area in the Pilliga.

"In the next 12 months, I'm hoping to eradicate that last remaining fox which makes it possible for us to move the mammals into the wider-fenced area," he said.

"We also have a couple of additional (NSW extinct) species we're looking to reintroduce, one of which is the brush-tailed bettong which was recently reintroduced at the other project site in Mallee Cliffs."