You might think rabbits are cute and harmless… After all, they’re the beloved protagonists of some of our most cherished children’s stories! But when 13 of them were released in Australia in 1859, they triggered one of the most destructive biological invasions in history. Within just 50 years, rabbits had overrun two-thirds of the continent, stripping ecosystems bare and threatening native species. In this episode of Human Footprint, Shane Campbell-Staton meets historian Martha Sear to uncover the astonishing story of Australia’s rabbit invasion and the ecological nightmare it created. From the first release of the deadly Myxoma virus in the 1950s to more recent outbreaks, Shane explores how researchers used biological weapons against the rabbit plague… and why the struggle continues today, more than 160 years after rabbits arrived in Australia. Wildlife manager Ian Lenon and CSIRO scientist Tanja Strive help Shane understand how today’s experts are tracking rabbits and developing new biocontrol tools, and what the future might hold for Australia’s ecosystems.
It’s the biggest mammal invasion that’s ever happened on planet Earth as far as we know. Whoa. People talked about the land being covered by a moving gray blanket. Within 50 years they had covered two thirds of the Australian continent. They’re in our cartoons, they’re on our cereal boxes, and all over our children’s stories. Rabbits are adorable. But bring them where they don’t belong, and you’re asking for trouble. This is the story of how 13 rabbits took over Australia, and how biocontrol helped us fight back. I’m Shane Campbell-Staton and this is Human Footprint. The rabbit has arguably been the most destructive nonhuman animal to ever arrive on the Australian continent. Woah. They have sent animals and plants to the brink of extinction and beyond. Rabbits aren’t native to Australia. And you’ll never guess how they got here. In 1859, Thomas Austin decided that he would like to do a bit of hunting on his country property. On Christmas Day in 1859, Thomas let 13 rabbits out. You know the exact day! Yep. We know the day, we know the number. From there they ran wild. Australia was like an all-you-can-eat bunny buffet, and they reproduced, well, like rabbits. The environmental and economic costs of this bunny bonanza were staggering. Rabbits eat plants from top to bottom, roots included. So before long, there was nothing holding the soil down. Cities and towns were blanketed with huge dust storms liberated by the little incisors of the bunnies. Of course, people also figured out a way to make a profit off of them. Just a heads-up in case you’re squeamish, the rest of this episode’s got quite a few dead rabbits in it. But I promise, they’re part of a remarkable story. So let’s get back to it. They went in the freezer, and they got shipped off to feed people in Europe. And rabbit meat was just the beginning. If you had walked through the streets of London in the 1920s, most of the gentlemen who lifted their hats to the ladies were wearing Australian rabbit fur on their head. But all that trapping barely made a difference. And rabbits reached plague proportions. So Australia turned to its scientists to find methods of biological control, and that’s where you get the story of myxomatosis. Myxomatosis is a rabbit disease caused by the South American myxoma virus, a relative of smallpox. Researchers wondered if myxoma could solve Australia’s rabbit problem. They were cautious, first making sure myxoma couldn’t infect any native species, and then testing the virus in small, isolated rabbit populations. Myxoma was finally unleashed in early 1950. And by the end of the year, people began to report hundreds, then thousands, and ultimately millions of dying rabbits. The piles of dead rabbits were stinking out pastoral properties. And the spread traveled hundreds of kilometers in just a few short months. Months! Woah, okay. Months, it was a big success. More than 99% of myxoma-infected rabbits died. Agriculture and ecosystems rebounded as the rabbit population crashed. It’s one of the most successful examples of biocontrol – using one species to control another – in history. But 70 years later, rabbits are still an inescapable part of Australian life. We have got quite a healthy population of rabbits, in our urban reserves within Canberra. Ian Lenon is a wildlife manager. He’s using heat-sensitive cameras to help locate and dispatch rabbits. Everyone behind the shooter. Ooh! Yep, you got him. That’s a female rabbit by the look of it. Okay. It’s hard to watch. But the rabbits killed in these control programs provide important data. What are you testing for here? So we take blood, for example, we can analyze that later for antibodies against the various viruses that are circulating. Okay. So we can see what was active in the area. And it turns out, myxoma is still here. So why hasn’t the virus finished the job? Biological control is not an eradication tool. It’s a management tool. Meet Tanja Strive. When she’s not spending time with her very pampered chickens, she’s working at CSIRO, Australia’s national science agency, on the next generation of rabbit biocontrol. Because myxoma isn’t as effective as it used to be. There is a window of time where the biting insects can pick up the disease and transmit it to the next animal. So as soon as the rabbit’s dead, it’s of no interest to a mosquito anymore. Okay. The first strain of myxoma was actually too lethal for its own good. It killed so quickly that it limited its own transmission. But new strains evolved that killed their hosts more slowly. Since the less deadly strains spread more easily, they gradually replaced the older strains. Just like the more infectious delta and omicron variants of COVID-19 replaced earlier strains of that virus. Today, myxoma virus probably still kills a very large amount of rabbits. But on its own, it would not be sufficient. So we need to continuously look for alternative tools and strategies. One of these alternatives emerged in the 1990s. So the calicivirus causes an infectious hepatitis. It’s one of the most virulent viruses that we know to affect mammals. It was on track to be released, but it actually got away from an offshore island in Australia where they were doing field trials. Luckily, the escaped calicivirus had already gone through rigorous testing to avoid unexpected impacts. And again, it was spectacularly successful. It knocked down populations by over 90% in some areas. Calicivirus is spread by flies feeding on dead rabbits. Unlike myxoma, it doesn’t need to keep its host alive, so it probably won’t become less virulent over time. But rabbits could still evolve resistance. And rabbits being rabbits, you only need to miss a few and they’ll build up again. So Australia’s using every tool they’ve got. Controlling invasive animals is not a solution that gives everyone the warm and fuzzy feelings. But if you don’t do it, the problem isn’t going to go away. Which leaves Australians in a tough spot. You don’t forget the sound of that crack, when the rabbit’s neck is broken. And even as a seven year old, I knew that the rabbits were decimating the populations of native animals and plants that I loved. But I could also see that those rabbits were themselves living things. It’s a very conflicted story for Australians. Humans change the world, sometimes without even trying, and often in ways we never intended. So we’re stuck making tough choices like this, with no easy answers. That’s just part of the Human Footprint.