Records set as multiple mammal reintroductions prove the value of rewilding

By all accounts, spring is the best time to visit Mount Gibson Wildlife Sanctuary’s sprawling 131,812 hectare slice of Western Australia, about 350 kilometres north-west of Perth.

It’s the wildflowers, locals say, which put on a bumper display for visitors to traditional lands of the Badimia and Widi people, who witnessed what was touted as the “best season in decades” after an unusually rainy winter in 2021.

But Mt Gibson is significant for other reasons, particularly its role in conservation research as a rewilding project.

The mammoth ecological restoration effort is owned and managed by the Australian Wildlife Conservancy, a donor-funded not-for-profit aiming to conserve native Australian animal species and their habitats.

This month, 11 western quolls – chuditch in the Noongar language – were moved to Mt Gibson, bringing the total number of species reintroductions at the site to 10, a record in Australian conservation.

Some reintroduced species live in the 7,800-hectare fenced-off ‘exclosure’, a refuge rendered free from feral predators, which hosts nine locally extinct mammal species, including the bilby, numbat, and woylie.

But not all translocated species live inside the fence. The seven female and four male chuditch moved house from nearby Julimar State Forest to live outside the exclosure at Mt Gibson.

Badimia elder Gloria Fogarty welcomed the chuditch to Mt Gibson with a traditional smoking ceremony.

“I think it’s gorgeous to have quolls back on my Country,” Fogarty said. “When they breed, well we’ll just go mad admiring the little critters.”

Sanctuaries in the southwest of WA have hosted rewilding programs using translocated and reintroduced mammals for some 30 years, says AWC regional ecologist Dr Amanda Bourne, who maintains oversight of the science programs at the sanctuaries.

Based at Karakamia Sanctuary in the Perth Hills, Bourne earned her doctorate at the University of Cape Town, South Africa, for research on the impacts of climate change on desert species in the Kalahari.

“Australian Wildlife Conservancy’s first sanctuary was in WA and Mt Gibson is one of the later properties that has come on board in the past 20 years,” Bourne says.

“It’s a site where we’ve had the most ambitious mammal reintroduction program to date, although a couple of the newer projects are sniffing at our heels now.“

Chuditch are only the second species to be introduced outside the fenced haven at Mt Gibson, after brushtail possums were first released both inside and beyond the exclosure in 2021.

As the largest marsupial carnivore in WA, chuditch will have a disproportionate but important influence on how the local ecosystems operate.

“We hope that they will go on to establish a population; we’ve been radio tracking them all week and they’re all still on the property and all still alive,” says Bourne, “so it’s all going well so far.”

Western quolls were once found across most of mainland Australia but were wiped out from eastern states by the mid-to-late 19th century, from Central Australia by mid-20th century and large parts of WA by the 1930s, according to the AWC.

Small populations of chuditch persist in the southwest of WA in the Wheatbelt, Goldfields and the South Coast.

Prior to their reintroduction, however, they had been absent from Mt Gibson for perhaps 100 years.

What is rewilding, and can it help climate change?

Even the word itself – rewilding – seems to evoke nature with a capital N, a stumble into misted forests and primal experiences; furry critters in abundance.

A quick check of the dictionary reveals its meaning as “to return our world to a more natural state”.

First use of the verb to rewild was by Newsweek reporter Jennifer Foote in a 1990 article on radical environmentalism.

In the decades since, it has emerged not only as a familiar headline but underscores the mission of dozens of conservation organisations worldwide.

In fact, rewilding projects are flourishing in Australia, including not-for-profit Arid Recovery, running a 123 km² wildlife reserve in South Australia’s arid north, and the WWF’s Rewilding Australia, with a mission to return missing faunal links across the nation.

Indigenous-led projects abound on Cape York in Australia’s north, while at the tip of South Australia’s Yorke Peninsula, Marna Banggara claims to be a unique rewilding initiative: not a closed reserve but part of a working landscape.

In practice, rewilding conservationists return species to ecosystems where they’ve become extinct due to hunting, habitat loss, degradation, or other pressures.

According to The International Union for the Conservation of Nature, rewilding “rebuilds ecosystems that have previously been modified by human disturbance, using the plant and animal life that would have been present had the disturbance never occurred”.

Importantly, rewilded ecosystems may help mitigate climate change, by “increasing carbon removal from the atmosphere and protect against climate change impacts by reducing soil erosion and flood risk”.

But use of the term and practice of its principles can be inconsistent. In recent times, NSW Parks and Wildlife has preferred terms such as ‘wildlife restoration project’, ‘feral predator-free areas’, or ‘reintroduction of locally extinct mammals’.

Critics point to rewilding failures, where detrimental effects arise for animals and the environment, prompting IUCN to develop 10 principles to guide rewilding initiatives.

Friction has arisen overseas where divergent views of wildness, naturalness, and place clash, notably UK farmers affected by these projects.

AWC’s model is based around the ownership or co-management of land for conservation, and it now owns, manages or works in partnership on more than 12.9 million hectares.

Its program is mostly built around the establishment of safe havens, fenced areas or islands from which cats and foxes – even goats at Mt Gibson – have been eliminated.

“As of 2023, AWC manages 10 safe havens,” says AWC’s Chief Science Officer Professor John Kanowski, “to which a total of 16 mammal species have been reintroduced, with another three mammal species reintroduced to two sites where predators are intensively controlled, but not eliminated.”

Chuditch is only the second species to be introduced outside the fenced haven at Mt Gibson, after brushtail possums were first released both inside and beyond the exclosure in 2021.

“We are in a vulnerable part of Australia in terms of climate change, from a drying and warming perspective,” says Bourne.

“Some species have done particularly well, and others have not established as confidently.

“For woylies [brush-tailed bettongs], for example, we introduced about 150 animals five or six years ago, and there are thousands now, whereas the greater stick-nest rats, we introduced about 50 and there’s probably about 50 of them now.

“So they’ve sustained themselves, but haven’t exploded in the same way the woylies have.

”Trying to understand such complex dynamics and how to facilitate population increases for the species that are taking longer to establish, is a big part of the challenge.

“We considered what feral animal activity is going on outside, and we have attempted to manage that through a trapping and baiting program.

“Then [we] intentionally reintroduced a couple of species, which we know are robust to fox and cat presence; [because] they occur in the wild in other parts of Southwest WA. Common brushtail possums were first; we reintroduced a few over the past couple of years both inside and outside the fenced area to see how they would go; they were our test case.”

“We introduced about 150 [woylies] five or six years ago, and there’s thousands now, whereas the greater stick-nest rats, we introduced about 50 and there’s probably about 50 of them now. So they’ve sustained themselves, but haven’t exploded in the same way the woylies have.”

Dr Amanda Bourne

Bourne says the possums were known to be quite robust elsewhere in the face of cats and foxes.

“We wanted to see what would happen if we reintroduced a missing native mammal species into the environment outside.”

Many animals were therefore collared for tracking but registered zero known mortalities over two years.

“[That] gave us some confidence to try with the chuditch … another species we know is robust in the face of cats and foxes elsewhere, and that persists in natural environments around SW Australia.

“We reintroduced them outside of the fence only, because we have populations of their prey species still establishing within the fenced exclosure, which we don’t want them interfering with.”

The future

Many rewilders choose to focus on fauna that’s gone missing from Australian ecosystems.

Wildlife’s influence is broad: as WWF and AWC both note by way of example, bandicoots, potoroos and bettongs play a role as ecosystem engineers, “digging and turning over soil, improving water penetrability and spreading fungi that are essential for assisting plant communities to absorb nutrients”.

But the rewilding questions still to be answered are tough: is there a long-term plan? Which animals can brave it “outside the wire”?

How do we tackle landscape-scale issues, including feral predators and noxious weeds?

Can we upsize the research findings to rewild at scale, or must wildlife sanctuaries remain museums of extinct species?

“We’re not aiming to expand the exclosure at this stage,” says Bourne.

“We are aiming to understand the level of predation by introduced cats and foxes that some of the species we’d like to introduce can tolerate, and to figure out whether we can suppress cat and fox activity to that tolerable level so that at least some of the species can re-establish outside of the fenced area.”