The endangered bush predator, considered vulnerable nationally and extinct in NSW, is hard to track, making research challenging.

But a breeding program at Taronga Western Plains Zoo in Dubbo is beginning to turn that around, with the arrival of 17 joeys.

"We had high hopes because the species hasn't been in a formal breeding program for about 20 years," wildlife conservation officer Rachael Schildkraut told AAP.

"It's a massive win for the program."

Chuditch, a Noongar name thought to have come from the animal's sharp cry, are considered high-order predators in the Australian ecosystem, naturally controlling populations of other species and cleaning up the bush.

It is one of the top 20 priority mammals for conservation under a national strategy, with feral animals and land clearing major threats.

Conservation teams brought four females and four males from Western Australia and South Australia in April and rehomed them in enclosures on the zoo's 100-hectare woodland sanctuary.

Two litters of six joeys and one litter of five were recently discovered among three pairs staff have been able to check on.

Ms Schildkraut says the chuditch, also known as western quolls, will be left to raise their young, monitored through cameras.

"The joeys are only tiny. Like all marsupials they give birth to very small neonates, so they're only a centimetre-and-a-half in length.

"We're hoping to see pouch bulges as they grow and develop."

The offspring will be released into rewilding sites, fenced areas in national parks free from foxes and feral cats, early next year.

The births are good news for conservationists after the release of the damning State of the Environment report, which shows listings of threatened species are increasing.

The report says Australia is not spending enough to recover vulnerable species, and is increasingly reliant on expensive measures of last resort to prevent extinction.

Ms Schildkraut says Taronga's program is looking for the best place to release the animals, and is planning to expand.

"It's rewarding to know that straight away we've had a tangible impact on the wild population."

Australian Associated Press