Koalas are now an endangered species in New South Wales, with the Koala Foundation estimating their numbers have declined by 41 per cent in the three years until 2021.
But what if there were pockets of bushland where they exist in significantly larger numbers than expected?
Two citizen scientists have photographed and named nearly 80 previously undocumented koalas on the southern outskirts of Sydney at Heathcote National Park, across the road from the more famous Royal National Park.
The discovery has raised the possibility there could be more koala colonies out there.
"One day, we went for a bit of a poke around the western part of Heathcote National Park, and we thought maybe there are some koalas around here," nature lover and koala spotter Steve Anyon-Smith said.
Koalas notoriously hard to spot
Four or five koalas located during initial searches with fellow spotter Tom Kristensen quickly grew to 32 over three months.
They are now close to sighting 80 individual koalas, with the possibility of many more in the immediate area.
"We've always known there are koalas in this landscape because their favourite food trees are here," Mr Anyon-Smith said.
"But you don't just stumble across them. You really have to search for them.
The pair said they catalogued each individual with a photo of their unique face and gave them a name.
Why the area naturally supports koala colonies
Mr Kristensen was convinced a search beyond the boundaries of Heathcote National Park would locate more.
"It's a relatively small area, but it adjoins a lot of other wild areas," he said.
"We've got Holsworthy military base, we've got the water catchments down there [in the Illawarra and Southern Highlands], across the highway, we have got the Royal [National Park].
"The koalas seem to be doing well here, possibly because there's a good supply of water coming from the Woronora Dam.
"There is a permanent environmental flow, so they can always find somewhere to have a drink."
The NSW National Parks Association (NPA) is one of several organisations committed to the protection of koalas, so the new population is a welcome find.
NPA executive officer Gary Dunnett said Mr Anyon-Smith and Mr Kristensen put in the time to make the find.
"I think that what we have seen over recent decades is a string of koala records from Heathcote, " he said.
"But it was only when Steve and Tom actually put the days and weeks in that people realised it was more than just the occasional vagrant from further out west, the big population out near Campbelltown.
"And what we actually have is a vibrant population right here sitting in the shadows of Sydney at Heathcote."
Koalas returning after bounty hunter era
Saul Deane from Sydney's Total Environment Centre has kept a close watching brief on the Campbelltown population in south-west Sydney.
He believed koalas were now returning to lands where they used to live before being driven out by bounty hunters in the 1920s.
"They were almost hunted to extinction — like the Tasmanian tiger," Mr Deane said.
Mr Deane would like to see research into koala numbers in the Water NSW Special Areas, which are closed to the public to protect water storage and infrastructure for Sydney and the Illawarra.
He would also like to see research into how underground mining in these areas could impact koala health.
"It's completely likely there might be a consequence, and that is an area where research would be encouraged," he said.
Area earmarked for more protection
A spokesperson for the NSW Department of Planning and Environment said it was working on listing 20 new asset-of-intergenerational-significance declarations within the national park estate for koalas by 2026.
The declarations are intended to protect the most important habitat for threatened species, but there is no detail yet on where that will occur.
"The koala populations of south-west Sydney and the Southern Highlands have been identified for investment and action in the koala strategy, and details will be released once finalised," the spokesperson said in a statement.
