Australian Outback Is Overrun as Rabbit Population Reaches Plague Proportions

In the Australian outback the hills are alive with rabbits--hundreds of millions of them.

Forty years after the disease myxomatosis almost rid the world’s driest continent of the imported pest, the rabbit population is back in plague proportions and growing by the second.

Farmers fear that the Southern Hemisphere summer just beginning will bring disaster on the scale of the 1940s, when rabbits regularly ate their way through the nation’s crops.

Estimates of the rabbit population start at about 200 million, the last official estimate in 1988, and spiral toward 1 billion.

Farmers in New South Wales, Victoria and South Australia say the threat posed by rabbits is the worst in a generation. One farmer hired professionals who shot 60,000 rabbits in one month on his 41,000-acre property in the west of New South Wales.

“They’ve done more damage than any other single thing in Australia’s history, and they now have a population to do it all over again,” said Howard Moxham of the New South Wales Farmers’ Assn.

Three years of unseasonally heavy rainfall have increased grass and plant growth on marginal land, allowing the rabbit’s fabled breeding capabilities to run rampant.

“Rabbits present the worst threat to the environment New South Wales has faced in 40 years,” said farmer Dick Palmer.

“The impact of rabbits is one of complete devastation. They breed and breed . . . and eat everything in their path.”

Wild rabbits were introduced to Australia when a farmer in Victoria named Thomas Austin set free 13 of 24 rabbits sent over from Britain to breed for sport.

“The portents are very worrying,” said Brian Cooke of South Australia’s Animal and Pest Control Commission.

“Normally rabbits breed for three to four months, but that’s been extended to eight or nine in each of the past three years because of good rains.”

A female rabbit can breed every month of the breeding season. Assuming a five-month season, in theory it is possible for a single pair of rabbits to have produced more than 62,000 descendants by the end of three seasons.

While wet weather is the main culprit, the decreasing effectiveness of myxomatosis, an infectious viral disease, in reducing the population is adding to the current problems.

Scientists estimate the mortality rate of infected rabbits is now about 60%, compared to 99% when the virus was introduced in the early 1950s.

The myxomatosis virus, carried by mosquitoes, has also spread less effectively in the drier “outback” areas away from the coast.

Farmers are again looking to science to find a solution to the present plague, but that will take time.

The government-financed Commonwealth Scientific and Industrial Research Organization said it will take at least five years to develop a new genetically engineered myxomatosis virus, which it hopes will kill rabbits and sterilize the survivors.

Fleas carrying the virus will be dropped into warrens where, it is hoped, they will transmit it throughout the colonies. The plan is to make the virus about 60% to 70% effective, so the virus can survive and reinfect successive generations.

“It will have a built-in long-term efficiency,” said a spokesman. “The rabbits won’t become immune because they will die from something unrelated to the disease they contract.”

Farmers are pinning their hopes in the near term on viral hemorrhagic disease (VHD), which is transmitted among rabbits by direct contact, resembles influenza in its effects and has cut a swathe through Europe’s rabbit population.

Australian authorities are carrying out stringent tests before letting that virus loose here, but the Commonwealth Scientific and Industrial Research Organization, which is not involved in VHD’s development, does not believe it is the solution.

“It won’t have the same long-term efficiency because the young will quickly develop immunity,” its spokesman said. “We expect the rabbit population to bounce back after an initial slump.”

Meanwhile, officials are concentrating on persuading farmers to attack rabbits with everything they’ve got. They are also urging environmentalists to take the problem seriously.

Farmers are being urged to rip out or blow out warrens, and to try poisoning the rabbits when all else fails.