How 20 Rabbits Released in 1859 Became a Continent-Scale Ecological Disaster

The 1859 Rabbit Release That Became an Australian Plague

In October 1859, Thomas Austin, a settler in the British colony of Victoria, released a crate of European rabbits on his estate near Geelong so that he and his friends could hunt them for sport. The mixed shipment of wild and domestic animals—about twenty rabbits, according to the most commonly cited figure—was placed in a fenced area. They did not stay there.

That single decision produced one of the fastest recorded invasions of a mammal species into a new territory. By the early 20th century, rabbit numbers had reached tens of millions across southern Australia. By the late 1940s, an often-cited estimate put the population at about 600 million, helped by a run of wet years and wartime disruption of fence maintenance and control programs. DNA research published in PNAS in 2022 traced the spread at roughly 100 kilometers per year and linked the entire invasion to Austin's original release.

The ecological damage was severe. Rabbits overgrazed native vegetation, accelerated soil erosion and competed with sheep and native marsupials for food, contributing to declines in several native species. Western Australia built a rabbit-proof barrier of more than 3,200 kilometers, but it largely failed to stop the westward spread. Australia then turned to biological controls, introducing myxomatosis in the 1950s and rabbit hemorrhagic disease virus in the 1990s; both worked at first but lost force as rabbits evolved resistance.

What Biology and Biosecurity Explain About Australia's Rabbit Plague

A Sporting Estate Was the Spark, Not the Cause

Austin's intent was modest: to recreate British-style rabbit hunting. As with many invasive-species cases, the critical piece of the story is not the animal alone but what was missing from its new home. Australia offered mild temperatures, soft soil for burrows, abundant grass and no predators that had evolved to hunt European rabbits. Ecologists call this the enemy release hypothesis, formalized in a 2002 Trends in Ecology & Evolution paper. The breeding biology of rabbits—females can become pregnant again within a day of giving birth and reach maturity in a few months—turned that freedom into explosive growth.

Myxomatosis and RHDV Won Early Battles, Not the War

The 1950s introduction of myxomatosis initially killed roughly 90% of affected rabbit populations and is considered one of the most dramatic successes in biological control. The long-term outcome was more sobering. A 2019 Science study confirmed that surviving rabbits carried genetic resistance while the virus became less lethal over successive generations—a textbook evolutionary arms race. The 1990s addition of rabbit hemorrhagic disease virus, still used alongside the older virus, has kept numbers down without eliminating the problem.

Biosecurity as Institutional Memory

Australia's current border controls for live plants and animals, among the strictest in the world, are a direct institutional response to the rabbit disaster. The episode is a reminder that a species that looks unremarkable in its native range—where predators, parasites and hard winters keep it in check—can behave very differently once those limits disappear. The main analytical point is that rapid growth was not a property of rabbits alone but of an environment that offered nothing to stop them; the control outcomes demonstrate that evolutionary responses will eventually blunt any single biological weapon.