Rabbit (ecology)In their natural environment and in captivity, rabbits are a benign, even useful species. When introduced by humans into other environments that have not evolved natural defences against them, however, rabbits can cause enormous damage. The best known example is the continent of Australia.
Rabbits are the most serious mammal pest in Australia, an invasive species being responsible for the extinction of about as many native animals as the fox, and causing millions of dollars worth of damage to agriculture each year. They were originally introduced with the First Fleet in 1788, but the major infestation appears to have been due to 24 wild rabbits released by Thomas Austin on his Southern Victorian property in 1859, for hunting purposes.
Rabbits are extremely prolific, and had no true predators to keep numbers down, so they spread rapidly across the southern parts of the Australian continent.
Within ten years of the 1859 introduction, the original 24 had multiplied so fast that 2 million a year could be shot or trapped without having any noticable effect. Rabbits reached the New South Wales border in 1870. Fifteen years later they entered Queensland, and by 1900 the rabbit was firmly established nationwide. It was the fastest spread ever recorded of any mammal anywhere in the world.
The effect on the ecology of Australia was devastating: One eighth of all mammal species in Australia are now extinct (rabbits being the single most significant factor), and the loss of plant species will probably never be fully appreciated. Rabbits cause huge damage to agricultural economy. They are also responsible for serious erosion problems, preventing native plant growth to the point of extinction, impacting biodiversity, and ruining gardens.
Nowadays, landholders are legally bound to control rabbits to reduce impact on the land and local life. They can attempt to control rabbits through death, fertility control or exclusion, but the only really significant checks in rabbit numbers have been biological. Myxomatosis was released into the rabbit population in 1950, causing estimated rabbit population to drop from 600 million to 100 million. Genetic resistance in the remaining rabbits led to the population recovering to around 200-300 million by 1991. To combat this trend, CSIRO scientists released rabbit calicivirus in 1996. However, it was not as successful as myxomatosis: it was estimated to have been fatal to only 65% of infected rabbits, as opposed to 99% for myxomatosis.