Australia has had a problem with European rabbits since their introduction to this isolated continent in the late 19th century. It is estimated that there are approximately 200 million feral rabbits in Australia.
Introduction of Rabbits to Australia
As previously mentioned on this blog (in this post), European rabbits were introduced into the Australian wild in 1859 so that they could be hunted. Thomas Austin, a wealthy settler in Victoria, had 13 wild rabbits sent to him and he let them roam free on his estate. From this small group of rabbits it took just 50 years for the animal to spread across the entire continent. That is simply amazing.
There were so many that they destroyed crops and land, leading to soil erosion. They also contributed to the decline of native plant and animal species. As recently as 1999 the Australian government’s main environmental legislation still listed the effects of feral rabbits as a “threatening process.”
Rabbits adapt very easily. All rabbits need is soil to burrow and short grasses to graze on. Since these conditions are fairly easy to come by even in the desert and outback areas of Australia. The other thing that makes rabbits so adaptable is their famously rapid and constant reproduction rate. The rabbit population soon became a plague for Australia.
Dealing with the Rabbit Plague
Scientists, farmers, and others have all attempted to get rid of Australia’s rabbit problem. Experts have tried Several techniques have been tried to manage the rabbit population, including fences, poisons, and even introducing diseases; with varying degrees of success.
One of the earliest attempts to control the rabbits was the building of fences. This was done by farmers as well as the government. They even constructed a fence along the entire Western Australian border (north to south). But the rabbits were already in the state so that fence only served to keep them there.
Up to the present day farmers have continually tried to take away the place where the rabbits breed and raise their young – by destroying the rabbit warrens. This method is only effective for controlling rabbit populations found on local and easily accessible land.
Poisons and Disease
Poisons were once a common method for controlling the rabbit population. Many types of poison have been tried including strychnine and arsenic. One of the main chemicals used to poison rabbits is sodium fluoroacetate, which has a very high mortality rate—more than 90 percent. Carbon monoxide and phosphine are also used to fumigate burrows.
In the 1950s, almost one hundred years after the introduction of rabbits, the government turned to what was effectively biological warfare against the rabbits. They released rabbits infected with myxoma into south eastern Australia. This was the first time a virus had been deliberately introduced to the wild to eradicate an animal. The myxoma virus leads to myxomatosis, a disease that only kills rabbits. Although many rabbits died they eventually developed an immunity to the virus and it became ineffective.
This was a huge experiment in natural selection on an incredible continental scale; and it had failed. If scientists wanted to wipe out the rabbits, they were going to have to try something else.
Rabbit Hemorrhagic Disease Virus (RHDV) is another rabbit-specific pathogen that scientists created in the 1980s. This disease is caused by an RNA (ribonucleic acid) virus transmitted by flies, and it can kill rabbits in 48 hours once contracted. In 1995, this virus was said to have escaped a quarantine facility and made its way to the wild. (Hmm… it does make you wonder eh?) It was officially released a year later in 1996. RHDV (also called calicivirus) lowered rabbit numbers in Australia by up to 90 percent in especially dry areas. But because flies were the main spreader of the virus the disease did not affect rabbits that live in cooler, wetter regions. Also, as with the myxoma virus, the pesky rabbits soon began to develop resistance to RHDV.
And so it continues…
It is a constant battle to control the numbers of rabbits while not destroying the Australian wildlife and landscapes. Introducing viruses into the wild is still thought to be the best, most cost-effective way to reduce rabbit numbers. So called “experts” are still working on new, more deadly strains of RHDV. The non-indigenous and extremely disruptive rabbit remains a huge problem in Australia. Finding a solution to control their numbers is still imperative.