600 Million Rabbits & Myxomatosis

Rabbits are poor conservers of energy. They can’t adapt to drought. Their diet is not diverse. All in all, they are not well suited to the Australian environment. But when it comes to reproduction they can’t be bettered. Mating takes 30 seconds, courtship included. In a single year, one doe can generate as many as 100 rapid-rooting offspring.

By 1950, the number of rabbits in Australia had reached 600 million. They devoured pastures and crops, ringbarked trees and spread erosion with their burrows. Shooting, poisoning, blasting, gassing, trapping, fencing, using ferrets or foxes and turning them into hats had all failed to make the slightest impact on their Malthusian multiplication.

Biological weapons were tested and failed. In 1888, Louis Pasteur sent a team from Paris armed with chicken cholera. It didn’t work. Myxomatosis, a pox from South America, was proposed in 1919. The government rejected the idea on the grounds that it “wouldn’t work”.

Eventually, the CSIRO decided to give it a shot. In May 1950, a myxo-infected bunny was released at Gunbar in the Riverina. Through the winter, members of the wild- life research section tracked the progress of the virus. In August, they returned to Canberra “despondent, cold and wet”. The disease worked in the warrens where it was introduced, but it didn’t appear to spread.

Three weeks later, a case was reported in Corowa, more than 200 kilometres from Gunbar. By summer, it was in Queensland, spreading so fast the scientists couldn’t keep up. The initial mortality rate was 99.5%. The smell of rotting flesh was everywhere in the bush. Within a year the rabbit population had dropped to 100 million.

The virus was spread by mosquitoes. So, too, was Murray Valley encephalitis, a virus potentially fatal to humans. It was a wet year, 1950, and there were a lot of mozzies. When people started dying, the CSIRO was blamed. To allay public concern, Australia’s most prominent scientists, Dr McFarlane Burnet, Prof. Frank Fenner and Dr Ian Clunies Ross, had themselves injected with myxoma.

Within five years, the small number of resistant and immune rabbits had become a large number of resistant and immune rabbits. The “accidental” release of calicivirus in 1995 again reduced Australia’s rabbit population but the impact eventually began to wear off.

The Foundation for Rabbit-Free Australia promotes the Easter Bilby as an alternative to the Easter Bunny. Also known as the rabbit-eared bandicoot, the bilby is a marsupial omnivore known to eat baby rabbits. CSIRO scientists also invented Aerogard and Softly.