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Fly Neighbourly Advice for the Tasman National Park

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Public comment is invited on the draft Tasman National Park Fly Neighbourly Advice. The draft Fly Neighbourly Advice has been prepared by the Tasmania Parks and Wildlife Service in response to increasing air traffic over the Tasman National Park.More

Hybrid diesel-electric shuttle buses at Cradle Mountain - a first for National p

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When you next visit Cradle Mountain you will be able to step aboard one of the new hybrid, diesel-electric, shuttle buses on your trip to Dove Lake. These new buses will reduce emissions and deliver a quieter, all mobility friendly, visitor experience.More

AFAC Independent Operational Review of the 2018-19 bushfires

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Following the 2018-19 bushfires the Tasmanian Government commissioned an independent report by the Australasian Fire and Emergency Service Council to review the overall response and identify areas where more can be done to improve the State's response andMore

Macquarie Island Pest Eradication Project

FAQs

Why is Macquarie Island special?

  • rabbit and warren on the island
  • rabbit warrens in the hills on the island
Macquarie Island is an Australian sub-Antarctic island located 1500 kilometres southeast of Hobart, Tasmania. It is the only island in the world composed entirely of oceanic crust and rock from the Earth’s mantle. The island’s remote and windswept landscape supports vast congregations of wildlife, and was inscribed on the World Heritage List in 1997, in recognition of its geological significance and outstanding natural beauty.

Macquarie Island is one of only a very few islands in the Pacific sector of the Southern Ocean where fauna in the region can breed. Around 3.5 million seabirds and 80,000 elephant seals arrive on the long, thin strip of mountainous terrain each year to breed and moult. Fur seals are re-establishing populations on the island after nearly being exterminated by commercial sealing operations in the early 19th century. 

The island was declared a Wildlife Sanctuary in 1933 and designated as a State Nature Reserve in 1972, in recognition of its important sub-Antarctic flora and fauna; including several species not found elsewhere—such as the royal penguin.  In 1977 it became a UNESCO Biosphere Reserve and in 2002 was listed on the Register of Critical Habitat. It is the only island under Australian jurisdiction that provides a breeding habitat for the wandering albatross and the grey-headed albatross, both of which are considered as vulnerable to extinction.
These numerous designations reflect the importance of the reserve’s natural values, and why it’s necessary to protect them for future generations.

The Tasmanian Government’s Parks and Wildlife Service (PWS) manages the island as a nature reserve, and manages its World Heritage values on behalf of the Australian Government.  The Australian Government maintains an Antarctic Division research station and a Bureau of Meteorology weather station on the island.  

What problems are caused by introduced species?

Over many years significant damage to vegetation was caused by rabbits on Macquarie Island. Vegetation communities are a critical part of the Macquarie Island ecosystem as they protect soil and rocks from weathering, stabilise steep slopes and provide habitat for invertebrates and burrow-nesting seabirds. In 2006 landslides caused at least partially by rabbit grazing, buried penguins and damaged visitor boardwalks. Rabbit numbers have fluctuated on the island since their introduction. Impacts have fluctuated with peaks in the islands’ rabbit population.

Rodents had a significant impact on the island, as they ate plant foliage, flowers and seeds, which prevented seedling recruitment. As there are no trees or shrubs on the island, all bird species must breed on or in the ground, where they were vulnerable to predation by ship rats. Rats ate the chicks and eggs of burrow-nesting petrels. Mice and rats also prey on invertebrate species.

Was the eradication of cats responsible for the increase in rabbit numbers?

No, not solely. A combination of factors was involved, and the removal of cats was probably a relatively minor one. These factors included the removal of a major predator, feral cats, resistance to the myxoma virus leading to reduced effectiveness within the island's rabbit population, and the unavailability of new stocks to continue spreading the virus. Importantly, vegetation recovery in the 1990s following successful rabbit control by myxomatosis provided an abundance of food to support an expanding rabbit population after the effectiveness of myxomatosis waned.

What did the eradication project involve?

The eradication of rabbits, rats and mice on Macquarie Island should be seen as three specific eradications that were conducted concurrently, in order to maximise the efficient use of resources. The techniques used were based on those used to successfully eradicate introduced species on other islands and on the characteristics of each of the three target species.

In the first phase, helicopters spread pellet baits containing the toxin brodifacoum. Global Positioning System (GPS) units in the helicopters ensured accurate bait coverage. This process eradicated all of the rodents and removed a high proportion of the rabbits that had survived an earlier release of the Rabbit Haemorrhagic Disease Virus. This baiting methodology has successfully eradicated rodents from many islands around the world.

After aerial baiting, hunting teams followed up on the ground eliminating surviving rabbits by shooting, fumigating and trapping them. Dogs were used to indicate areas where rabbits were located. The dogs were critical in locating isolated rabbits in the rugged terrain of Macquarie Island.

How has the poison been selected?

The use of poisons is an accepted practice in dealing with pest species, as no other techniques have proven successful in eradicating rodents on large sub-Antarctic islands. Various toxins were considered and brodifacoum was identified as being the most suitable. The toxin is the same as that used in some rat poisons that are widely available for domestic use. Importantly, it has the best track record at successfully eradicating rodents from islands so reduced the chances of the project failing.

Were native animals be affected by aerial baiting?

The need to minimise impacts on native species was been an important consideration in all planning. The baiting was conducted in winter when most of the native animals had left the island, thus avoiding or minimising effects on their populations.

However, some mortality of non-target species was expected as this has been the case in other island eradication programs. An Environmental Impact Statement was prepared to assess the likely impact of the project and this identified that some bird species would be at risk from primary poisoning as a result of ingesting baits and secondary poisoning from scavenging on dead animals that have eaten the baits. Of the bird species native to Macquarie Island, 80 per cent were unaffected by baiting.

Trials conducted on the island with non-toxic baits showed that most native bird species were not interested in the pellets, although some gulls consumed them. In the event, the five species assessed as being vulnerable to poisoning did sustain impacts, although none were threatened at a population level. All impacted species have been successfully breeding in the years since the aerial baiting was implemented.

Eradicating rabbits and rodents has vastly improved conditions for native species, and at least 28 native bird species were expected to increase in population, following the successful pest eradication. Evidence of this has already been recorded, with the return of blue petrels breeding on the main island, and increases in the number of Cape petrels and soft-plumaged petrels.

When did the aerial baiting occur?

The winter months were the best time to conduct aerial baiting for the following reasons:
  •     Many of the native animals depart the island for winter
  •     Rabbit and rodent numbers decline during winter due to a lull in breeding and higher mortality, meaning there are fewer animals to target and fewer need to be killed
  •     There is a greater chance the rabbits and rodents will eat the baits, as there is less vegetation available for them to consume at this time of year
  •    It avoids the summer tourist season so tourism operators will not be affected.

How long did the eradication project take?

The aerial bait drop was scheduled for winter 2010. Unfortunately, adverse weather conditions prevented completion of the aerial baiting and it was completed in winter 2011. After aerial baiting, three years of hunting and monitoring ensured the eradication of surviving rabbits and rodents. The field component of the project was completed in April 2014.

Is it too late – have the values of Macquarie Island been lost?

The natural ability of the island ecosystem to restore itself has been demonstrated by the revegetation evident within fenced exclosure plots, and the return of grey petrels to breed on the island in 2000 following eradication of feral cats. Removal of the pest animals that had caused the decline in the island’s values will, in time, give the island environment the conditions needed for recovery. The robust recovery in vegetation and birdlife in the period since rabbits and rodents were successfully removed has clearly demonstrated the ability of natural processes to restore the values of Macquarie Island.

Will the island need to be revegetated once rabbits are removed?

Macquarie Island has harsh growing conditions for plants and recovery of some vegetation communities may take decades. Exclosure plots constructed on the island since the 1960s have demonstrated that the rate of vegetation recovery can be high in favourable sites. Because of that recovery, no revegetation activity is needed, and in the period since aerial baiting was completed a dramatic recovery of vegetation communities has been recorded at numerous sites around the island. (see a series of photos of an exclosure plot constructed in 2006 - PDF 786Kb).