How the rabbit plague took over Australia

The study, led by the University of Cambridge and CIBIO Institute in Portugal, in collaboration with the University of NSW, revealed how rabbits took over Australia's landscape.

Rabbits were first introduced to Australia when five domestic animals were brought to Sydney on the First Fleet in 1788. 

At least 90 more importations were made, but none became invasive until 1859 when Thomas Austin imported 24 wild rabbits from his family's land in the UK to his estate near Geelong in Victoria.

Within three years 'Austin rabbits' had multiplied to thousands and by the beginning of the 20th century, the "grey blanket" had spread over the country at a rate of 100km per year - the fastest colonisation rate for an introduced mammal ever recorded.

The study findings, published in the journal Proceedings of the National Academy of Sciences, show invasive rabbits descended from Austin's imports wreaked havoc across the continent.

Study co-author Professor Mike Letnic from UNSW said scientists often lacked detailed information about where invasive animals came from.

"But in the case of wild rabbits in Australia, they are very well documented as one of the most successful biological invasions in the world," he said.

Research now showed a genetic pattern in Australia's rabbit populations demonstrated that certain genetic types were predisposed to be successful invaders.

Lead author Joel Alves from the University of Oxford and CIBIO Institute said "it was the genetic makeup of a small batch of wild rabbits that ignited one of the most iconic biological invasions of all time,".

Researchers analysed historical records alongside new DNA collected from 187 European rabbits - mostly wild-caught across Australia, New Zealand, Britain and France between 1865 and 2018. 

They found most mainland Australian rabbits derive from Austin's 24 wild rabbits.

"We managed to trace the ancestry of Australia's invasive population right back to the South-West of England, where Austin's family collected the rabbits in 1859," Dr Alves said.

"Despite the numerous introductions across Australia, it was a single batch of English rabbits that triggered this devastating biological invasion, the effects of which are still being felt today."

Rabbits introduced to Australia before 1859 were often described as tame, with fancy coat colours and floppy ears - traits associated with domestic breeds.

Austin rabbits were described as wild-caught and explains why they better adapted to local conditions, with changes in body shape to help control their temperature.

"So, it is possible that Thomas Austin's wild rabbits, and their offspring, had a genetic advantage when it came to adapting to these conditions," Dr Alves said.

Despite rabbit-proof fences, the introduction of the deadly myxoma virus and other measures introduced to control populations, rabbits remain a major threat to native flora and fauna, costing the Australian agricultural sector an estimated $200 million a year.

The research also provides insights for managing invasive species.

"We need to be more careful that we always have appropriate quarantine measures ready to try to stop new biological invasions from occurring," Prof Letnic said.