Macquarie Island

Back in May 2007, an article entitled ‘World Heritage Embarrassment’ was published in the Tasmanian Conservationist (#311), highlighting the stand-off by the Tasmanian Government on funding for a program to remove rabbits, rats and mice from Macquarie Island and its credibility on nature conservation in one of the most important reserves in Australia.

The following two articles are from the Macquarie Dispatch Issue 11, published in August 2012, recount just how successful the program has been, once it got off the ground. The articles are printed with permission from the Tasmania Parks and Wildlife Service.

No let-up in the hunt for rabbits

In the nine months since the last rabbit was found and dispatched on Macquarie Island, there’s been no let-up in the hunting team’s efforts to ensure that any remaining rabbits are removed from the island.

As reported in the previous Macquarie Dispatch, a total of 13 rabbits have been found and killed since aerial baiting finished in July 2011. The last rabbit killed was in November 2011 and project manager Keith Springer is confident that rabbit numbers are now extremely low, with a ‘best guess’ estimate that there may be fewer than five rabbits remaining on the island.

A fresh team of hunters joined the effort in April 2011 with four of the 2011/12 team selected to stay on with the project. Peter Kirkman is this year’s eradication team leader after joining the project last year as assistant team leader under Peter Preston. The eradication team includes six hunters and six dog handlers.

The team’s first month on the island was taken up with familiarisation and training in recognising rabbit signs such as grazing, scratchings and droppings and in hunting techniques including trapping, fumigating burrows and shooting. The dog handlers were paired with the dogs in an effort to find the best fit of skills and personalities. Each of the dogs has different skills; some are good on rock stacks, some for ranging at a distance from their handler, and some are best for close work in the thick tussocks. 

The island is divided into six hunting blocks, with dog handlers and hunters tackling one block for a four-week period. Each block has two huts and the teams roam between the huts, returning to the island’s station at the end of the month’s field work for four days of catching up on emails, phoning home to loved ones, socialising and resting. Peter downloads all of the GPS units carried by the hunters and coordinates the combined tracks onto a map. In June 2012, they covered 2,233km in their search for rabbits and a map produced of their patrols since August 2011 shows that only the steepest slopes and lakes and tarns are exempt from their attention. Since August 2011, the hunting team has clocked up an incredible 33,412km  in their search for those rabbits that found the bait unappetising and survived.

Of course, as time goes on the job gets much harder, with so few rabbits remaining. Although the winter weather is very hard on both dogs and people, it has its advantages for locating rabbits – a light cover of snow highlights any rabbit tracks or droppings, and the shorter days and long nights are ideal for spotlighting. With each growing season, the vegetation will continue to recover and finding sign of rabbits will be that much harder. It’s also hard to know which rabbit is the last.

Progress toward the eradication goal is reviewed annually based on the principle of continuing hunting for two years after the last known rabbit is accounted for.

Winners and losers in vegetation recovery

That Macquarie Island is rapidly recovering from the incredible devastation that resulted from the grazing pressure of a rabbit population estimated at greater than 100,000, is indeed heartening, but the question is, how long will it take for a new ecological equilibrium to become established?

Senior ecologist with the Department of Primary Industries, Parks, Water and Environment (DPIPWE), Dr Jennie Whinam is among those who have seen the island at its worst and are now keenly documenting the recovery.

DPIPWE scientists started monitoring the island in the 1980s and are now analysing 30 years of vegetation data up until the beginning of the eradication program. They hope to travel to the island this coming summer and begin recording the vegetation recovery.

What was obvious to all who visited Macquarie in recent years was just how bad the island looked as its most charismatic species, such as the megaherbs and large tussocks, largely disappeared from some areas under intense grazing pressure.

What was worse, according to Jennie, was the landscape-scale ecological changes.

‘The island had changed to a very simple island. It was a much less exciting and complex mosaic of landscapes and vegetation and the specialness of it had gone with the loss of the iconic species,’  Jennie said.

It had become so bad that staff on the island had fenced off known populations of certain species like the prickly shield fern (Polystichum vestitum) in the hope of preserving them for the day when the island was free of rabbits.

‘At this time the rabbits were so hungry they started burrowing under the fence to eat the rhizomes. What is just so amazing now is that, in some areas that weren’t fenced, people are seeing the tiny little fronds starting to unfurl.’

While the island started ‘greening up’ within six months of the removal of rabbits, scientists acknowledge that ecological recovery will be a long process.

‘The thing about sub-antarctic and alpine environments is that things happen slowly...but the photos I’ve seen so far just bring joy to my heart. With one of the photos sent to me of the native silver leaf daisy, Pleurophyllum hookeri, I realised I’d never seen a landscape of pleurophyllum that didn’t have rabbit damage, so to see an entire hillside of it without a single bit of rabbit damage was very exciting.’

While Jennie is confident that the island will look significantly different in as little as five years’ time, she is mindful of the message from colleagues involved in other sub-antarctic island restoration projects – expect the unexpected.

‘The sleeper is what will happen with the weeds. There are three weed species on the island and we’re expecting some of them to increase initially and then hopefully decrease as the native species re-establish. What we don’t know is whether there have been new arrivals that have gone unnoticed simply because it’s been very hard for us to identify plants when they were so heavily grazed.

‘The initial response will be fast and lush, but it’s likely to be 20 years before we can start talking about what the new ecological equilibrium will be.’