Rabbits in Australia
Rabbits in Australia
Imported into Australia in the mid-nineteenth century, rabbits have overrun much of the country, causing extensive agricultural and environmental damage and demonstrating the dangers of introducing non-native species into an area. Before the first humans arrived in Australia, the only mammals living there were about 150 species of marsupials as well as bats , rats, mice, platypuses, and echidnas. The chief predator in Australia today is the dingo, a wild dog introduced about 40,000 years ago by Australia's first human settlers, the Aborigines. When the British settled Australia as a penal colony in the late 1700s, they brought a variety of pets and livestock with them, including rabbits.
The problems with rabbits began in 1859, when 12 pairs of European rabbits were released on a ranch. Since no significant numbers of natural predators were present in Australia, the rabbit population exploded within a few years. They overgrazed the grass used for sheep raising, and despite extensive efforts to reduce and control the population, by 1953 approximately 1.2 million mi2 (3 million km2) were inhabited by between several hundred million and over one billion rabbits.
The rabbits have caused considerable damage to Australia's environment , especially its native plants and wildlife . Their extensive burrows cause soil erosion , and they eat large quantities of grass and shoots of other plants, devastating native flora that birds, insects, and other creatures depend on for food and cover.
Repeated attempts have been made to exterminate the rabbits and limit their populations, often by fumigating and ripping up their burrows, or by using poison bait. The most effective effort undertaken involved the introduction of myxomatosis in the 1950s, a disease that is fatal to rabbits. But after an initial decline, the rabbit population began to recover, and much of Australia remained overrun by the animals.
Proponents of eradication say that the most promising new biological agent to control wild rabbits is know as RCV (rabbit calicivirus), which is thought to be a new disease, and has killed farmed rabbits in China and Europe. In its early stages, it kills over 90% of infected rabbits. In the laboratory, it has been shown to kill rabbits shortly after infection; and after 31 different native species were exposed to the virus , it did not appear to be capable of infecting non-target animals. But the certainty of this is disputed by other scientists, who worry that release of the virus is "an uncontrollable and unpre dictable" biological experiment; that it could eventually jump the species barrier, especially if it mutates into a different form; and that rabbits will eventually develop resistance to the virus, as they did to myxomatosis.
The elimination of rabbits might even have adverse consequences, such as removing an important food source from eagles and other predators who have come to depend on them. Wild dogs and cats, deprived of their normal prey, may turn to increased hunting of kangaroos and other marsupials. On the other hand, the number of feral canines and felines might decline with the demise of an easy and abundant food source, which would benefit marsupials. So, the ultimate impact of RCV is not entirely predictable.
There is little danger of an immediate collapse of the rabbit population. The latest data estimates that the population has been reduced from about 200–300 million rabbits to 100 million.
The proliferation of rabbits in Australia has cost the government and ranchers billions of dollars. This situation remains a primary example of the harm that can result from the introduction of non-native species, no matter how seemingly harmless, into a foreign environment.
[Lewis G. Regenstein ]
Anderson, I., and R. Nowak. "Australia's Giant Lab." New Scientist.