Conservationists say the release of more than 100 woylies beyond the safety of a predator fence is a big, if bold, step towards repopulating the endangered species in Western Australia's remote Wheatbelt.

The animals were released "beyond the fence" at Mt Gibson Wildlife Sanctuary, 350 kilometres north of Perth, last week, following several decades of work to restore the population in the protected area.

Once found across mainland Australia, the population of woylies — or brush-tailed bettongs — fell by almost 90 per cent due to land clearing and invasive species brought about by European settlement.

In the Wheatbelt, the local population was believed to be extinct for more than 100 years.......

.......The population at Mt Gibson has grown to more than 1,000 animals from the 162 introduced in 2016....

.....A number of woylies have also climbed the sanctuary's 2-metre fence in recent years, kick-starting the repopulation by themselves.

"We see them on the camera traps with females with large pouches carrying young and young at heel," Dr O'Neill said.

"The young are growing up and surviving on the outside."

Forty of the woylies were fitted with radio collars so that ecologists could track their movements outside the fence.