‘We can not afford to get this wrong’: relocating Leadbeater’s possums is risky – but it’s their only chance | Endangered species

As dusk has fallen each night for the last seven days, Dan Harley and Arabella Eyre have turned to each other and said: “They’ll be coming out about now.”

A week ago, the pair executed a risky plan to relocate five tiny Leadbeater’s possums – each about as heavy as an apple and the size of a fist – from their last remaining bolthole in Victoria to a new home in a forest swamp, three hours’ drive away.

“With only 33 left we can not really afford to get this wrong,” says Dr Harley, a senior ecologist at Zoos Victoria. “There’s a very high risk and you need a lot to go right for them to succeed.”

This tiny and critically endangered marsupial is Victoria’s faunal emblem, thought lost forever until their rediscovery in 1961.

Land clearing and logging since European invasion has decimated the possum’s habitat of mountain ash swamps. The 2009 Black Saturday bushfire burned almost half of their remaining habitat.

Two genetically distinct Leadbeater’s make up the species and are categorized either as a highland or lowland variety. Harley says there are likely just a few thousand of the highland possums left – a frighteningly low number.

But the existence of the lowland possum – thought extinct until rediscovered in 1986 – is even more precarious.

Dan Harley putting up a nest box for Leadbeater's possums.
Dan Harley putting up a nest box for Leadbeater’s possums. Photograph: Victoria Zoos

It has been clinging on in a strip of forest just 4km long and about 100 meters wide at Yellingbo Nature Conservation Reserve – about 50 kilometers east of Melbourne’s CBD.

Harley has been monitoring that group for 25 years. Numbers are now so low that there is no need to estimate them. Each one is documented. There are just 33 left, including the five that were translocated a week ago.

Modeling suggests that with such a small number left in the wild – and with no success breeding them in captivity – the lowland Leadbeater’s will be extinct within a couple of decades.

One single bushfire could be the end of them. Under global heating, that risk is rising. For the lowland group, a translocation has become more and more urgent.

“But the alternative is we just monitor them until extinction,” says Harley. “We’re at the point where the risk of doing nothing is greater than the risk of getting it wrong.”

A new home

Last Tuesday at dawn, after the possums nestled down for their daytime sleep at Yellingbo, the 5cm entry holes were blocked off with a rag. The possums inside had already already had tiny radio transmitters attached a few weeks before.

The boxes, containing two family groups with five individuals, were taken down, driven three hours to a forest near Mansfield in the state’s north-east, and secured a few meters up on mountain swamp gums.

While it was still light and the possums were still sleeping, Harley’s colleague Arabella Eyre pulled out the rag and sneaked down the ladder.

“It feels like a crazy rush and there’s some adrenaline pumping. I leave as quietly as I can, ”says Eyre, a field officer with Zoos Victoria who has been working with the Leadbeater’s possum for five years.

To help them get started, Eyre and Harley have been putting out food for the new arrivals (a mix of nectar, protein powder and egg). That will be slowly scaled back.

Arabella Eyre radio-tracking the Leadbeater's possums.
Arabella Eyre radio-tracking the Leadbeater’s possums. Photograph: Victoria Zoos

Each day – “like a benevolent big brother” – Eyre has been spending hours reviewing camera footage of the possums at their den boxes and feeding stations and checking transmitter data.

She’s been having dreams about them and wonders if the possums are aware they’re being watched, or if they ever think how the food arrives. “I do often wonder that. But I do not think they ever hear me. “

Harley describes the possums as “like a creature from Tolkien’s Middle-earth” that emerge in twilight like “little sprites”.

“They’re super fast and super quiet. They’ll appear, and then they’re gone and you do not hear a thing. “

Eyre says the new site could theoretically support up to 100 new possums, but given their shockingly low numbers there are only so many the team can relocate.

“It comes down to the possums to breed up their numbers,” she says.

As part of the work of the possum’s recovery team – which includes the Victorian Department Department of Environment, Land, Water and Planning and Parks Victoria – the whole eastern side of the state has been surveyed looking for places for translocations.

‘Drastically altered landscape’

In late 2020, 11 were taken to a large patch of forest at Wallaby Creek. But in just three months, the team started to find radio collars without a possum attached.

Cats had likely taken seven and on New Year’s Day 2021 the decision was made to launch an emergency evacuation to catch and return the remaining four possums to the relative safety of Yellingbo.

The possum’s predators at that failed translocation site were dominated by feral cats, but at the new site it is mostly invasive foxes. Harley thinks wild dogs in the area could be keeping the foxes busy, reducing the risk for the possums.

A second translocation took place last November to test the new site. The eight pioneering settlers are still there, and there are babies.

Harley says the tactics to save the possum were originally thought of as a sequence, with habitat restoration and breeding in captivity coming first – each one taking five years or more. Translocation was to be the last step.

“But we need to do this all concurrently. We spent millions restoring habitat but we didnt do it fast enough. We need to be aggressive and proactive now, ”he says.

“It’s the lack of these swamp forests that we keep banging up against. They’re pasture now and people forget they used to be forests.

“We’re searching for solutions in this drastically altered landscape.”

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