Island and Isolated Populations

Small sections of isolated bushland in Australia support populations of wild Koalas that are perceived to be in abundance and ‘out of balance’ with their natural surrounds. Some of these places occur on small offshore islands, where humans have introduced Koalas to landscapes outside of their natural range. Other ‘island’ populations are on the mainland; originally supported by continuous vegetation which has been segmented from tree-clearing.

This has created unusual 'zoo–like’ situations, and Koala populations with reduced genetic diversity.

Quick facts

  • ‘Island zoos’ confuse people into thinking that all Koalas are ‘flourishing’
  • ‘Island zoo’ populations may not be viable and are subject to crashes
  • ‘Island zoos’ occur in landscapes that are now degraded and often diseased
  • It is not a viable, nor sustainable option to ‘top up’ threatened mainland populations with KoalaKoaland zoos’
  • Highly-modified landscapes are in an ecological ‘mess’ far worse than most people, including authorities, realise.

Examples of populations perceived to be problematic occur at Framlingham Forest, Mt. Eccles, Sandy Point, Raymond Island, French Island, Snake Island, Tower Hill and Kangaroo Island. A few of these are described in more detail below.

Land use, management and ecological histories are highly complicated at these locations. Unable to disperse, Koalas become ‘trapped’ in isolated remnants (like Framlingham Forest). In many instances, trees are dying, including Koala fodder species, and are not being replaced by new seedlings. Understorey and ground cover layers are disappearing. Koalas may exhibit strange behaviour and congenital defects.

Reports of ‘exploding Koala populations’ and forest dieback dominate the media, with calls by some scientists to kill, sterilise and/or relocate the animals. In Victoria, controversial management actions occur within the context of 80 years of Koala translocations. Read more here.

 

Raymond Island

Of the 760 hectares that make up Raymond Island, located on the Gippsland Lakes in

Victoria, one third is public land. Koalas did not originally occur on the island, and were first introduced in 1953 from Phillip Island. Today’s population is thought to suffer ill-health, high levels of inbreeding and an inabilty to disperse (Koalas need to move around in order to seek out territories and mate). Recently, the community raised concerns when an unconfirmed number of Koalas (up to 300) died mysteriously within a 12-month period. This highlights the risk of population crash—or even local extinction—that these island zoo populations face and why it is misleading to describe them as ‘flourishing’.

Salinity is an apparent land degradation issue on Raymond Island, as is the monoculture spread of exotic plants and other weedy species like Bracken Fern and Sweet Pittosporum. Forest dieback has been observed, including the loss of native groundcover and understorey layers. In general, the health of the island’s Indigenous flora has been described as extremely poor and as being in steady decline for many years. At some locations, whole areas are in poor health or dead. Many species are reportedly suffering dieback - the phenomenon that extends beyond the eucalypt species browsed by Koalas. Koalas may be suffering bracken poisoning, and the displacement of the formerly-diverse understorey may be influencing dieback. It has been suggested that the bracken’s competitive root system may starve and stress other species.

 

Mount Eccles

Mount Eccles National Park is a 6223 hectare isolated remnant of Manna Gum woodland situated in southwest Victorian farming country. Like most of the state, the surrounding landscape has been substantially cleared of its original vegetation. Thirty Koalas were introduced from Phillip Island in 1973 and 47 Koalas from French Island in 1982. Having been cut off from formerly connected habitat, today’s Koalas are unable to naturally disperse to other bushland. Recent ad-hoc responses to perceived overpopulation and over-browsing have included the relocation of surgically-sterilised and non-sterilised Koalas to other areas. Monitoring of the translocated Koalas’ fates did not commence until 2003 and indicated most subsequently died or were taken into veterinary care.

 

Snake Island

Koalas were introduced to Snake Island and, following perceived population explosions, have since been sterilised, ferried to the mainland, transported by car, then released without monitoring by the Victorian Government. Members of the community were alarmed when they found dead animals with ear tags and maggot-infested sutures. The technique has subsequently changed, with Koalas sterilised, released back on the island, then later recaptured and translocated. For decades, introduced cattle and deer have inhabited the island, inhibiting native vegetation (especially eucalypt) regrowth.

 

Kangaroo Island

Kangaroo Island is a large island off Australia’s southern coast. Much of the island is cleared farmland used for crops and sheep grazing. Europeans settled there more than 200 years ago, at which time there were no Koalas on the island.

In the early 1900s, millions of Koalas were slaughtered in Queensland, New South Wales, Victoria and mainland South Australia to satisfy the fur trade (link). The species was driven to extinction in South Australia within 20 years. Koalas were later introduced to Kangaroo Island from French Island in Victoria and have since become a major tourism draw card. Forest dieback has been observed on the island, but no research appears to have been conducted to determine whether Koalas are the primary cause. Research into dieback is urgently needed. Dying trees, for instance, may produce more sugars, thereby attracting Koalas to them.

Disease, habitat fragmentation, poor fire management and salinity are amongst the many possible contributors to tree deaths on Kangaroo Island. Feral animals and weeds wreak further havoc, while feral bees oust native birds and other pollinators from their tree hollow homes. The tree-killing fungus, Phytophthera, was first identified on Kangaroo Island in 1994; trees began dying in 1995.

 

Framlingham Forest

Framlingham Forest, located north of Warrnambool in Victoria, is an isolated 2710-hectare forest fragment dominated by Manna Gum and Messmate Stringybark. It was historically managed for timber production before being handed back to its traditional owners, the Kirrae Whurrong people, in the 1970s. Likely to have originally occurred in the area, Koalas were reintroduced to Framlingham Forest in 1976. But like most parts of Victoria, the majority of forests in the Framlingham area had been cleared by early settlers for grazing pasture. This dramatically transformed the landscape, leaving Framlingham Forest an isolated, island habitat in a sea of agriculture. Today, the forest suffers the effects of isolation, the most evident being dieback associated with ’edge effects’

Edge effects occur where forest edges are subject to increased wind exposure, insect attack, farm runoff, impacts of feral and production animals and tree disease. In forest fragments as small as Framlingham, these edge effects can extend to all parts of the forest, a phenomenon which has already occurred in some parts of Framlingham. Many of the forest’s Manna gums have died en masse. Koalas have often been exclusively blamed for the ill health of Framlingham when the problems are more likely to reflect the forest’s long, complex history of poor land management and ecological breakdown.

The Australian Koala Foundation, together with the Framlingham Aboriginal Community and volunteers, is replanting (link) areas using local native species and conducting revegetation trials.

 

Pressures on ‘cut-off’ Koalas

Another piece in this complex puzzle is the role of natural selection in highly-modified environments. Koalas inhabiting isolated remnants within their natural range, like Framlingham Forest, might be experiencing rapid changes in their biology and behaviour. Although scientists suspect such changes, the extent and nature of them is not known.

An example of a biological trait under pressure might be the inclination to disperse; a Koala that leaves to establish its own territory does not survive and go on to produce similarly-driven offspring. The result is the habitat remnant supports a population of Koalas whose instincts tell them to stay put. Population crashes might occur due to one, several or a suite of cumulative effects. (eg reduced genetic vigour). The fact that these Koalas are taken and moved elsewhere as part of translocation programs may explain why the same ‘problems’ have been reproduced in recipient habitats. Simultaneously, accelerated changes may be occurring within the vegetation, including the eucalypts that Koalas feed on, and therefore affecting the rest of the ecosystem. Without massive large-scale revegetation and repair of the environment, these kinds of problems will continue to quietly escalate.

 

Cause & effect

Tree dieback is a complex phenomenon, in which causation and correlation are often confused. Scientists suspect a range of potential underpinning causes, which in many instances may be cumulative; ranging from salinity and loss of understorey, to fragmentation, inappropriate fire management, weeds and disease. The effects and full extent of the introduced Phytophthera fungus—a known tree killer—is not known, but the disease has been confirmed in locations in at least five states. There is a pressing need for concerted research into dieback and for vegetation scientists to communicate the results of their research. In ecosystem conservation, flexibility and adaptive management are key. Land managers, planners and scientists need to acknowledge what ‘works’ and what ‘doesn’t work’, learn from past decisions, and develop long-term strategies and visions. In contrast to this, the Victorian translocation program responsible for creating problematic zoo-like populations is described by the state’s current government as “highly successful” and “arguably one of the most successful native animal conservation programs in Victoria's history.” These problems are the direct result of past management decisions embedded within the context of local and regional environmental degradation trends.

 

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The threat to mainland battlers …

Data collected from 1,109 field sites by the Australian Koala Foundation confirm the vulnerability of mainland Koalas across their natural range. But measures to protect these animals and their habitat are undermined by the attention given to the small number of these island 'zoos'.

These two entirely separate issues become confused to the extent that proposals addressing the constant threat to Koalas and their habitat on the mainland are, at times, rejected by influential conservation scientists, governments and their scientific advisers. Even the Victorian Government’s own Koala experts describe the state’s Koala population as “large and thriving” based on the perceived contribution by zoo-like islands and isolates in spite of the risks of local extinction.

Some scientists promote the seemingly dispassionate view that surplus animals (in some cases entire introduced populations) should be culled. Some politicians, on the other hand, promote a sensitivity to global criticism and impacts on Koala tourism. In the heat of the moment, few people step back to look at what has created the situation in the first place: bigger issues of broad-scale habitat restoration, habitat protection and sustainable landuse and the underpinning causes of forest dieback. The confusion and public outcry generated by calls to kill, sterilise and / or relocate Koalas fuels ongoing debate within and between conservation, scientific and political circles.

Meanwhile, ad-hoc, short-term management actions and experiments continue to be implemented, with misconceptions and misinformation reiterated in their justification. Messages of ‘exploding Koala populations’ linger longer and more prominently in the minds of Australian citizens, media and decision-makers. This undermines efforts to educate people about the seriousness of threats facing surviving Koala populations within the Koala’s original range on the mainland. Associated portrayals of Koalas as 'environmentally-destructive' perpetuate the simplistic notion that it is culturally permissible to blame one species for complex ecological breakdowns and imbalances resulting from centuries of unsustainable land use.

 


Island Populations Q&A

 

Why can't the excess koalas just be relocated to the mainland?

This solution is not as simple as it sounds. It is a costly and labour-intensive exercise. As well, there are enormous implications when you 'dump' koalas into habitats that may or may not have stable koala populations already residing there. Koalas live in socially stable groups and the relocation of Kangaroo Island koalas to new areas would have to be carefully researched and carried out so as not to destabilise the social structure of any existing population. Koalas newly released into the territory of an established population would most likely be forced out of that territory. Alternatively, inbred animals could take up the valuable habitat of genetically healthy koalas.

Where are the koalas to be released?

Koalas are fussy eaters and may not find the eucalypts in the release area to be palatable, even though they may be the same species they have been eating. Different soil types affect the toxicity of leaves in trees of the same species. One of the most suitable places to release these koalas would be the south east forests of South Australia. But extensive clearing is currently underway in those forests, which makes them an unsuitable or dangerous environment for koalas.

Because the Kangaroo Island koalas are Chlamydia-free, they have no natural immunity to the disease. If they were introduced onto the mainland they would immediately be in danger of contracting chlamydia from the existing mainland populations.

Although relocations have been done in the past, there is no scientific evidence to say they have been successful. Relocating could be just a "soft cull" - the animals may ultimately die anyway. It would just take longer and no-one would see it happening.

What about sending the excess koalas to zoos?

Australian and overseas zoos and wildlife parks, as well as landholders in Australia, have offered to take the koalas. In addition to the relocation problems mentioned above, this could set a dangerous precedent, and could result in koalas from the wild being sold for profit. It also takes the pressure away from protecting koala habitat. Loss of habitat is undoubtedly the greatest threat to koalas in the wild today. Australia has one of the highest landclearing rates in the world and there are those who use the 'too many koalas on Kangaroo Island' argument to justify the continuation of landclearing in other parts of the country.

What if the excess koalas were shot?

There are some scientists and others who suggest that shooting koalas would be the best solution. Besides being totally unacceptable to most people, this would only be a short-term solution. All the conditions which caused the problem in the first place would still be present. Overpopulation would quickly recur. The Federal Minister for the Environment has assured the public that koalas on Kangaroo Island won't be culled. Imagine the international outrage if the SA Government went ahead with this plan.

Koala culling would also take the focus away from habitat protection. While this debate has ensued, wildlife authorities in South Australia and Victoria have resisted planting trees for fear that koalas would only eat them! The AKF believes this is nonsense.

What about artificial fertility control?

This is only effective for the life of each koala. It would have to be carried out on every new koala born into the population, and is expensive and labour-intensive.

What about instigating measures to preserve and propagate trees?

This could be achieved by commencing tree planting programmes in suitable areas, such as along creeklines, and then by fencing these areas so that the new saplings could grow without disturbance from sheep and other feral animals.

As the koalas are not native to the island (i.e. they are 'feral') shouldn't they ALL be removed?

This has been suggested by some people, and would certainly solve the problems on the island, but bearing in mind the points above, what would be done with the koalas which were removed? Tourism is a vital industry on Kangaroo Island and the koalas are an integral part of that. Thousands of tourists per year visit Kangaroos Island. Many islanders want to keep the koalas for their tourism appeal.

What is AKF's stance on the issue and what are we doing about it?

The AKF believes that the issue is not too many koalas, but not enough trees. We believe that Kangaroo Island has enormous land managemenrt problems. The "koala problem" is just one small facet of these larger problems. However, something does need to be done to address the koala situation.

The Australian Koala Foundation does not agree with culling. We are confident that there is adequate collective scientific knowledge to resolve the koala issues on the island dispassionately, and with the best long-term interests of the Koala and the Kangaroo Island ecosystem in mind.

The AKF is concerned about the koalas on the island and about the furore surrounding them, firstly, because the koalas are already in some distress, and secondly, because the notion of "too many koalas" is counter-productive to efforts to conserve koalas on mainland Australia where they face serious problems (many of which are also obvious on Kangaroo Island).

Talk of "too many koalas" has provided a loophole for politicians to make poor decisions with regard to koala habitat protection in the rest of eastern Australia. Most recently, the decision by the Australian Government not to list the Koala as "vulnerable" under the Endangered Species Act was, in part, due to the Victorian and SA positions of "too many koalas."

The so called koala 'overpopulation' is a man-made problem which could be solved with considered scientific assessment. There is no 'quick-fix' solution. The problems are complex and will require long-term thinking and consensus among koala experts, those from other disciplines such as botany and wildlife managers to manage populations such as Kangaroo Island. Planting more trees and good scientific management by stabilisation of the population are good starting points.

 

Perspective on the management of isolated Koala populations - by Deborah Tabart OAM, presented at the Australian Veterinary Association Conference 2000