RABBITS have jumped back into the spotlight as numbers grow and disease resistance to calicivirus builds.
And with control methods faltering, the cost to the environment and lost agricultural production is likely to soar past $200 million a year.
Manager of pest bait manufacturer Animal Control Technologies Linton Staples says "people at all levels" have taken their eye off the ball in rabbit eradication by riding on the coat-tails of biological methods and backing-off from other on-ground approaches - such as warren ripping, shooting and poisoning.
He said while virulent strains of calicivirus still kill a high proportion of rabbits, non-virulent strains are helping boost immunity levels in wild populations. Immunity to biological controls, a drop-off in conventional control methods and good seasonal conditions had combined to boost rabbit numbers.
"The calicivirus is still viciously lethal in killing unprotected, vulnerable rabbits within a couple of days, but it is virtually powerless to kill a rabbit with protective antibodies," Prof Staples said.
"The rabbit problem has been significantly underestimated at every level - from farmers to politicians," he said.
"This is a classic issue with pest management.
"People become complacent and back-off conventional control efforts, when pest numbers are low, because they are under the false assumption they do not have much of a problem.
"But in the case of rabbits, the virus that has been keeping numbers in check is losing its potency, and there is sufficient numbers to seed a new wave of rabbits.
"What we should always try to do is go after the small, remaining populations while numbers are low to prevent them bouncing back."
He said myxoma virus still kept rabbits in check and prevented the plague numbers of the 1950s developing, but lax control efforts meant numbers were high enough to cause significant damage to the Australian environment and agriculture.
Rabbits are spiraling out of control, particularly in Australia's south eastern coastal areas, and they remain the major pest in the pastoral zones.
"Rabbits are a serious, re-emerging threat and there is the real potential to turn Australia into a desert," Prof Staples said.
Invasive Animals Cooperative Research Centre data shows that just one rabbit for every two hectares is sufficient to prevent regrowth of succulent seedlings.
"For succulent seedling growth and revegetation, it is not good enough to have the rabbit problem under control for three years if, on the forth, numbers soar and the vegetation gets wiped out," Prof Staples said. IACRC was searching for more virulent strains of the calicivirus and other new viruses to control rabbits.
But Prof Staples said comments made by the late Frank Fenner - a pioneer of the myxoma virus in Australian rabbit control - were ringing true: that Australia was very lucky to have had two lethal control viruses, and the chance of finding a third was very low.
"We should not hold out hope for a third 'magic bullet' virus," he said.
*Full report in Stock Journal, February 23 issue, 2012.
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