The pouch young are the first eastern quolls born in the wild on the Australian mainland in more than 50 years.

Born to three different mothers, they will stay in their mothers' pouches for eight weeks before venturing out onto their mothers' backs, where they will remain for six weeks.

Eastern quolls were wiped out on the Australian mainland more than 50 years ago by feral animals and disease, and were only reintroduced to Booderee in March, when a group of 20 quolls bred in a Tasmanian wildlife sanctuary were relocated to the park in Jervis Bay.

Booderee National Park natural resource manager Dr Nick Dexter said reintroducing quolls to the area was always going to be "a risky venture" despite 15 years of intensive fox management at the park.

But he said the fact that 30 per cent of the female quolls had produced pouch young indicated it had been a success, and there were already plans to relocate up to 40 more eastern quolls from Tasmania next year.

He said the initial months of the program to reintroduce the native carnivore to Booderee had thrown up significant challenges; only four of the 20 quolls released in March survived after a combination of fox attacks and incidents on the roads.

But scientists, conservationists and land managers working on the project were confident the lessons they had learnt would make it possible to establish a sustainable population at Booderee.

"We’ve been able to target the foxes with either shooters or poison baits pretty quickly, but still, we’re looking to expand fox control into the Jervis Bay hinterland so that fewer foxes actually immigrate into the park," Dr Dexter said.

"We also lost quite a few, which we weren’t anticipating, to getting struck on the roads.

"They tended to use the roads to access different habitats and unfortunately, they appear to have very little road sense, so we’ve moved the survivors to an area that has much less traffic."

Dr Dexter said each of the adult quolls was being tracked with a GPS collar, allowing the team behind the program to quickly discover and manage threats, as well as the chance to learn about their movements, behaviour and preferred habitat.

Booderee National Park has worked closely with the Australian National University and Rewilding Australia on the reintroduction program. Organisations including the World Wildlife Fund and Tasmanian Quoll Conservation Society sanctuaries also played a part.

Australian National University researcher Dr Natasha Robinson said the project had already proven the key requirement that quolls could find food, shelter and breed at Booderee, making it a clear success.

"We've also shown a capacity to make changes to improve the quolls' survival rate," she said.