These rabbits have a price on their head of $600 million dollars. There may be only two of them now, but they don't say "breeding like rabbits" for nothing.

And the damage they cause is a multi-million dollar headache.

Thomas Austin introduced rabbits to Australia in 1859, for sporting hunters. But with no natural predators and litters of five or more baby bunnies seven times a year, soon there was a rabbit plague.

Farmers ripped their warrens, laid poison and shot them but still they multiplied. In the 1950's CSIRO introduced myxomatosis which killed millions of rabbits, but eventually the rabbits became resistant and by 1995 had multiplied to an estimated 300 millions. So again CSIRO scientists were asked to come up with a solution.

In March 1995, a quarantine station was set up on tiny Wardang Island off the coast of South Australia to test Rabbit calicivirus, which had kept down rabbit populations in Europe. It was due for release in 1998, but, after only 6 months, it escaped from the island, most likely carried by insects.

"There would have been a much bigger discussion phase about whether or not to release the virus and that was just left behind. But beyond that, the effects have been as good as we ever would have expected. In the arid zones we have had a remarkable reduction. The numbers of rabbits are down to ten or fifteen percent of their original numbers"

And as the rabbits disappeared, the barren landscape flourished once again.

There was some criticism about a reduction in food for foxes and eagles that could result in them turning to native fauna for food.

"Because the rabbit is an introduced species, I don't think that we can really sort of say that it should be maintained just to support some of our native animals. So I think we really need to look at the bigger ecological picture".

Up till now the calicivirus has been most successful in dry regions. So a study site has been set up in the Victorian town of Bacchus Marsh to discover why it too doesn't work as well in cold wet areas. Scientists are also aware that because myxamatosis was only effective for 15 to 20 years, rabbits could also become resistant to calicivirus even though so far the results have been more dramatic.

"We really don't know whether that is going to happen with calicivirus. I imagine that it could happen and I think it's important to take every opportunity to try and capitalise on the calicivirus while we have it".