Tasmania has no wild koalas — but could play a role in the survival of the species – ABC

By October 28, 2020 News

By Selina Ross         Posted 28 Oct. 20

Several koalas have roamed wild in Tasmania but the species has never established in the state.(Supplied: WWF Australia/Doug Gimesy)

Three Hummock Island sits 30 kilometres off the north-west coast of Tasmania, in the wild waters of Bass Strait.

The 70-square-kilometre granite island has stunning deserted beaches, a rich Aboriginal history and abundant wildlife.

There is just a smattering of buildings and caretakers are the only residents, but the island was once home to a handful of imported koalas.

Four adult koalas were released into the wild on Three Hummock Island in 1947 by the family that was leasing it at the time.

Four adult koalas were released into the wild on Three Hummock Island in 1947 .(Supplied: Gary McArthur)

Cissie and Bill Nichols ran the island as a farm from 1932 to 1951, when Eleanor Alliston and her husband took over for what became the longest period of European occupation.

Alliston told their story of living and raising children on Three Hummock in her insightful book Escape to an Island.

The book documented her determined yet fruitless search for the covert koalas.

“As we penetrated further and further into untrod places we always hoped for a glimpse of a koala bear,” she wrote.

As the only chronicler of the koala relocation, Ms Alliston detailed how the koalas were brought over from Victoria and put in the gum forest at the foot of Big Hummock.

“They never sighted any of them again, and it was supposed that they had died,” she regretfully wrote.

Tasmanian wildlife expert Sally Bryant said wildlife releases on islands were common at the time to help preserve species, including on Maria Island on Tasmania’s east coast.

“Forester kangaroos, Cape Barren geese were also declining in population and were released onto islands,” she said.

“It was really typical of the thinking in the 1940s, ’50 and ’60s.”

“Those sort of objectives were undertaken by the Parks and Wildlife Service, or the Animals and Birds Protection Board in those early days.”

Mountain marsupials

Three Hummock Island was not the first Tasmanian location where koalas were released.

Four adult koalas were let loose on kunanyi/Mount Wellington in 1862.

The Tasmanian Museum and Art Gallery (TMAG) said it was hoped then that if the species established in the state, they would provide food for lost bushmen and travellers.

Four koalas were released on kunanyi/Mount Wellington in 1862.(ABC Open Contributor Carmel Boyd)

Edward Wilson from the Victorian Acclimatisation Society said at the time, “for a man on an exploring expedition or lost in the bush [koalas would be] sufficiently good to eat and might perhaps save a life”.

TMAG reported that a few years later a man in Glenorchy — now a bustling suburb at the foot of the mountain — shot a koala that he found sitting on his back fence.

Dr Bryant said it was not surprising the quartet did not turn into a thriving population.

“It reflects the naivety of understanding of Australian animals,” she said.

“Particularly species like koalas that are very slow to breed and establish, four animals definitely would not have established with any certainty.

“Our knowledge today is so much better and relocations are done in a totally different way.”

Why aren’t koalas native to Tasmania?

Contrary to common assumptions, Tasmania is not too cold for koalas and their food is on offer.

A 2011 pest risk assessment by Tasmania’s Department of Primary Industries and the Environment stated that all but the state’s west coast provided an ideal climate for the marsupials.

Koalas have thrived in Tasmanian wildlife parks.(Supplied: Bernadette Camus)

“In addition, five species of eucalyptus, which are known to be preferred feed tree species of koalas, occur in Tasmania (eucalyptus globulus, E. viminalis, E. obliqua, E. ovata, E. radiata), and provide one or more potential food sources across most of the state,” the report said.

Despite that, no fossils have been found showing evidence of koalas having ever lived in the state.

Chris Johnson, an ecology professor at the University of Tasmania said the theory behind that related to Bass Strait.

Bass Strait used to be the Bassian Plain, the land connecting what became Tasmania to the mainland.

“Because of the climate at the time there probably weren’t trees on the Bass Plain,” he said.

“It was maybe a big, expansive grassland and shrubland.

“Because there were no trees, probably there was no way for a koala to find its way from Victoria to Tasmania.

“It would have been a long walk.”

Why don’t we set up a population in Tasmania?

The 2011 DPIPWE report looked at the impact koalas could have in the state if they were ever introduced.

It found that if koalas were brought to Tasmania there was a high risk of them establishing, with potential for “extreme consequences”.

The risk assessment detailed one main reason against their introduction: their potential to be pests in Tasmania’s forestry industry areas.

A 2011 government report found koalas had the potential to be pests in Tasmania’s forestry areas.(ABC News: Gregor Salmon)

Although the report said the actual risk of economic damage was not clear, it said koalas had a “demonstrated ability to have a major impact on the health of eucalypt forests in areas where they have been introduced and occur in high densities”.

The report said a number of the tree species preferred by koalas were important for Tasmania’s forestry production.

“Consequently there is potential for koalas to impact directly on forestry activities by browsing on trees being grown for harvest,” it said.

“In addition, the presence of koalas could cause an increase in forestry management costs by requiring koala management actions in timber production areas.”

The assessment concluded that koalas represented an extreme threat to Tasmania.

“Based on the outcome of the risk assessment it is recommended that koalas are not permitted entry into Tasmania,” the report said.

Tasmania could ‘play a role’

Dr Bryant said she was “a little gobsmacked” by the assessment’s verdict.

“It’s incredible the Government would assess an Australian species as an extreme threat, let alone the koala, which is now facing a risk of extinction,” she said.

Tasmanian wildlife expert Sally Bryant.(ABC: Jessica Hayes)

“Extreme threats are caused by pest species like fallow deer and feral cats, which continue to ravage the Tasmanian landscape, or ferrets for which there are currently no restrictions on keeping, breeding or selling in Tasmania.”

Dr Bryant said that while she was cautious about wildlife relocations, Tasmania could play a role in protecting koalas.

“Their food trees are here, they’re kept here in wildlife parks all around the state and have been for decades so we know that they can be maintained in Tasmania very easily,” she said.

“Wildlife parks have the skills to breed them, so we have the technology, we have the capabilities of holding a captive stock population for a recovery program if or when that was ever needed.

“If we were called on, I would think Tasmania should definitely put up its hand and assist.”

Posted 28 October 2020

https://www.abc.net.au/news/2020-10-28/why-are-there-no-wild-koalas-in-tasmania/12806032