Rabbits have been dying at Bon Bon in recent months – unfortunate for the rabbits, but this is good news for the environment.
This is the second wave of rabbit deaths we've seen since arriving at Bon Bon last February and we believe it's caused by rabbit calicivirus disease (RCD, also known as rabbit haemorrhagic disease RHD). It's encouraging to see that the disease is still effective at keeping rabbit numbers in check.
When the disease hits, it's quite dramatic as you can see many dead rabbits lying about on the ground. Fortunately for Bon Bon, this most recent outbreak happened in mid-September during quite dry conditions, when the local population was already under some nutritional stress. Rabbit numbers can explode in lush years and they die in their millions during dry periods. Diseases like RCD suppress the booms and exacerbate the busts – giving outback habitats a chance to recover from the intense grazing pressure that rabbits exert, and giving native animals a better chance at survival.
Rabbits have historically become a menace to the Australian environment by degrading vegetation and causing the loss of associated biological diversity. Despite some very good success with bio-controls such as myxomatosis and RCS, they continue to have a negative impact in the rangelands and on agricultural productivity in many areas.
According to a fact sheet published by the CSIRO, RCD is a viral disease which affects only European rabbits. It was first introduced into South Australia in 1995 with the aim of reducing rabbit numbers right across Australia. Since then, the disease has been most effective in the arid and semi-arid zones.
RCD is highly infectious and is spread by insects such as fleas, mosquitoes, bush flies, blowflies and also occurs by contact between infected rabbits and other susceptible rabbits. The infection causes acute symptoms and can kill the rabbit within 48 hours.
Researchers are not sure how long the disease will remain effective at controlling wild rabbit populations in Australia (i.e. how quickly the rabbits will build a natural immunity to the disease).
A recent article published in the South Australian Arid Lands "Across the Outback" newsletter (October edition) says researchers at Biosecurity SA have been studying the impact and management of rabbits, including the genetic changes in the rabbit calicivirus in Australia, while the Invasive Animals CRC's RHD Boost program has been importing new strains of the virus to test for the potential to improve the effectiveness of the disease.
We are making the most of the reduced rabbit numbers and the current dry season by destroying warrens in the homestead area.