Woylies may have been dubbed "rat kangaroos" because of their appearance, but the small nocturnal marsupials are far less resilient than either of those species.

The population of woylies has in fact shrunk by more than 90 per cent in the space of 15 years.

"The woylie is one of Australia's most endangered mammals," Australian Wildlife Conservancy (AWC) chief executive Atticus Fleming said.

"15 years ago there were 200,000 woylies. Today there are less than 18,000.

"If we don't do something really decisive, it will be another extinct Australian animal."

The woylie, weighing less than two kilograms and standing about 30 centimetres tall, once ranged across two-thirds of Australia.

One of the country's great "silent achievers" of the bush, the animals have played an important role in promoting the health of their environment.

But the AWC has blamed feral cats for the sharp decline in woylie numbers, with measures to control cats failing to reverse the trend.

"There are up to 20 million feral cats in Australia," Mr Fleming said.

"They're all killing — on average — five animals a night, so you can do the maths.

"There are tens of millions of native animals being killed by feral cats every night.

"At the moment, there's no silver bullet that is going to allow us to remove cats from the landscape.

"They don't readily take baits. Unlike foxes, they prefer to eat live prey."

Fate of woylies pinned on fence

A woylie has its radio-collar checked and tightened before being sent to the Mount Gibson enclosure. ( Supplied: Phil Tucak )

Tim Allard left the mining industry to oversee the construction of a 43-kilometre long fence surrounding an area of bushland at Mount Gibson, 350 kilometres north-east of Perth in WA's Mid West.

The fence is the culmination of years of work and cost $2 million to build. It represents the woylies' best chance of survival.

"It's got a skirt that sits on the outside, and that stops your foxes and cats getting in, and the animals on the inside from digging out," Mr Allard said.

"Then we've got a floppy top, and when the cats hang off that they'll fall back against the electric wires and get booted off.

"In addition, the electric wires are there to stop the cats climbing there in the first place."

Fenced enclosures have been established in other parts of Australia, but the WA project is the conservationists' most ambitious yet.

Nine species of endangered mammals will eventually call the 7,800 hectare feral-free enclosure home — including bilbies, wallabies and numbats.

"We can't continue doing what we're doing at the moment. Animals are becoming extinct as we talk," Mr Allard said.

The woylies have been the first to settle in, with ecologist Bryony Palmer and her team releasing more than two dozen creatures, each fitted with tracking collars so their progress can be followed remotely.

"If the woylie was still for a long period of time, the frequency of the beeps emitted by the radio collar changes," Ms Palmer said.

"Then we know we need to go in and check it out."

Getting back to the bush of old

It is hoped the group of woylies inside the enclosure will grow in number from 50 to 1,500 over the next decade.

That would represent an 8 per cent jump in the species' total population.

Scientists are trying to learn more about feral cat hunting behaviours in an effort to save animals like the woylie. ( Supplied: Australian Wildlife Conservancy )

"They should do really well," Ms Palmer said.

It has been half a century since woylies last lived in the Mid West.

Conservationists say the area has lost half of its mammal species over the past two centuries due to feral cats.

Within the next two years, the AWC plans to establish a campground nearby to allow members of the public to visit the enclosure, so they can step back in time and experience the bush as it once was.

Scientists will also be working nearby at the Neville Tichbon Field Research Centre, hoping to learn more about feral cat hunting behaviours and how to control them.

"What we're trying to do is find the Achilles heel of the feral cat," Mr Fleming said.

"In the longer term, we really do want animals outside of fences."