How Two Dozen Rabbits Started an Ecological Invasion in Australia

In Australia today, European wild rabbits eat through pastures and crops, reducing the land’s productivity and competing with native wildlife. The invasive species threatens around 300 kinds of plants and animals, per Nature News’ Smriti Mallapaty, and costs the economy $200 million in agricultural damage each year, according to Science’s Jack Tamisiea.

Now, a new genetic analysis shows that today’s 200 million rabbits may have originated with a single shipment of just two dozen.  

Published this week in the Proceedings of the National Academy of Sciences, the research supports a theory that historians had previously posited, writes the Guardian’s Donna Lu: the idea that Australia’s rabbit problem can likely be traced to one man’s estate. On Christmas in 1859, Thomas Austin, a wealthy English settler, received a shipment of 24 wild and domestic rabbits from his brother in England.

“That single event triggered this enormous catastrophe, ecologically and economically, in Australia,” Francis Jiggins, an evolutionary geneticist at the University of Cambridge in England and one of the authors of the new study, tells Nature News.

But this wasn’t the first time that rabbits were imported to the continent. According to historical records, the first European rabbits likely traveled to Australia with the first British colonizers in 1788, per Nature News. Over the next 70 years, about 90 separate rabbit introductions occurred in Australia.

It wasn’t until after Austin received his rabbits, however, that the creatures started taking over. Their population expanded across the country at a rate of more than 60 miles per year, covering the whole continent within half a century, per Nature News. In 1865, Austin told the local papers that he’d killed 20,000 rabbits on his property, according to Science.

To determine the infestation’s origins, the researchers conducted a genomic analysis of 187 European rabbits caught between 1865 and 2018 in Australia, Tasmania, New Zealand, Great Britain and France, per the Guardian. They found that most rabbits from the Australian mainland were genetically similar and had a mix of wild and domestic ancestry, reports Nature News.

The Australian rabbits also had several genetic similarities to rabbits in southwest England, where Austin’s family gathered the animals to send, per Science. The researchers examined mitochondrial DNA, which is passed down by the mother, to determine that many of the Australian rabbits descended from five females introduced from Europe, according to the Guardian.

Finally, the rabbits that were caught farther away from Barwon Park, where Austin lived, showed less genetic diversity, which also indicated to the researchers that the rabbit invasion could have originated there, per Nature News.

Austin’s imported rabbits had wild ancestry, which could explain in part why they thrived in Australia. Wild rabbits were probably better than domestic ones at avoiding predators and surviving in challenging terrain, Joel Alves, an evolutionary geneticist at the University of Oxford and co-author of the paper, tells Nature News. Plus, in the mid-19th century, humans were turning the outback into pastures and hunting rabbits’ predators, making it easier for these invaders to survive, Science writes.

Still, David Peacock, an ecologist at the University of Adelaide in Australia, doesn’t believe Austin should take all the blame for the rabbit infestation. In 2018, he co-authored a study theorizing that multiple rabbit introductions led to the species’ invasion. He tells Science that other rabbits were released in Australia at the same time as Austin’s.

But he does see value in studying the rabbits’ origins, as this knowledge could help eradicate populations of the invasive species. “The better [we understand] the origin, spread, and genetics, the better we can manage Australia’s most serious pests,” he tells Science.

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.