Rabbits in Australia

An old poison cart, which distributed poisoned baits to kill rabbits, Woolbrook, NSW

Shooting rabbits is one of the most common control methods and can successfully be used to keep already low populations in check whilst providing food for people or pets, though it is ineffective for large-scale eradication.

Destroying warrens through ripping (a procedure wherein rabbits are dismembered or buried alive as a bulldozer dragging sharp tines is driven over their warrens/burrows),[19] ploughing, blasting, and fumigating is widely used, especially on large farms (known as "stations"). The sandy soil in many parts of Australia makes ripping and ploughing a viable method of control, and both tractors and bulldozers are used for this operation.

Poisoning is probably the most widely used of the conventional techniques, as it requires the least effort and is capable of destroying a local population, though reinfestation given the mobility of the animal is almost inevitable. Laying baits of pollard laced with a phosphorus-based poison, such as "S.A.P." manufactured by Sayers, Allport & Potter, was an early method. The advantage of phosphorus is that in dry weather, assuming it has not been laid in clumps (obviated by use of a poison cart), it soon degrades to innocuous phosphoric acid and presents no further danger to livestock or pets. It does, however, present a real fire risk, and concentrated fumes can be toxic to operators.[20] More modern poisons for rabbit control are sodium fluoroacetate ("1080") and pindone.[21]

Another technique is hunting using ferrets, wherein ferrets are deployed to chase the rabbits out to be shot or into nets set over the burrows. Since the number of rabbits ferrets can kill is limited,[22] this is more a hunting activity than a serious control method. Although ferrets and other mustelid species are used as control measures, Australia has significantly fewer wild mustelids to prey on the invasive rabbits while in their warrens or burrows compared to Europe and the United States.[23]

Historically, trapping was also frequently used; steel-jawed leg-holding traps were banned in most states in the 1980s on animal-cruelty grounds, though trapping continues at a lower level using rubber-jawed traps. All of these techniques are limited to working only in settled areas and are quite labour-intensive.

Impact of rabbit-proof fence, Cobar, New South Wales, 1905

Ring-fencing can be highly effective way of providing a rabbit-free area. In the 1880s, James Moseley ringed Coondambo Station with wire netting and fenced off the watercourses; at the first heatwave, the rabbits perished of thirst. Shortly after 1900, he fenced off the deserted Yardea, Paney, Pondana, Yarloo, and Thurlga stations in the Gawler Ranges with 150 miles (240 km) of wire netting, turning them within a few years from degraded land overrun with rabbits into a profitable sheep run.[24]

Well-known modern examples, which also exclude foxes, dogs and cats are Warrawong and Yookamurra wildlife sanctuaries, pioneered by John Wamsley.

Two well-known examples of much more extensive fences are:

In July 1884, Ernest James Stevens, a member of the Queensland Legislative Assembly, proposed that the Queensland government erect a fence to prevent the infestation of rabbits in New South Wales from spreading into Queensland (his Logan electorate being very close to the New South Wales border).[25]

Gate in the Rabbit Fence at Stanthorpe, Queensland, 1934

In 1893, a rabbit-proof fence was commenced in Queensland. It was progressively extended through the years. In 1997, a final segment was built connecting it to the Dingo Fence. It extends from Mount Gipps (near Rathdowney) to Goombi between Chinchilla and Miles.[26]

The No. 1 rabbit-fence in Western Australia (1926)

From 1901 to 1907, the rabbit-proof fence was built in Western Australia between Cape Keraudren and Esperance to try to control the spread of the rabbit population from the east into Western Australian pastoral areas. Given that European rabbits can both jump very high and burrow underground,[27] a perfectly intact fence stretching for hundreds of kilometres, and whose gates farmers or graziers did not leave open for livestock or machinery, was still unlikely to succeed. As such, the Number 1 Rabbit-Proof Fence, which was erected in 1901, failed to keep the rabbit population away from the protected area.[28] Even after this large scale fence had failed, smaller scale fencing projects continued to make a successful appearance.[23]

Myxomatosis control trial, 1952

Releasing rabbit-borne diseases has proven somewhat successful in controlling the population of rabbits in Australia, but such success as has been achieved did not occur as quickly as was hoped.

An offer by the New South Wales government of a £25,000 reward for a biological control of rabbits attracted the attention of Louis Pasteur, who proposed using the chicken cholera bacillus (now known as Pasteurella multocida). Although that measure did not prove viable, the association with Pasteur accelerated the introduction of microbiology into Australia.[29]

On 16 April 1888, the New South Wales government appointed a royal commission "to make a full and diligent inquiry as to whether or not the introduction of contagious diseases amongst rabbits by inoculation or otherwise, or the propagation of diseases natural to rabbits ... will be accompanied or followed by danger to human health or life, or to animal life other than rabbits, or to interfere injuriously with the profitable carrying on of agricultural or pastoral pursuits ..." Under the aegis of the commission, tests were conducted at Rodd Island, and although rabbits who were given food adulterated with chicken cholera bacillus were killed, no evidence was found of the contagion spreading to healthy rabbits.[18]

In 1885, Professor Archibald Watson of Adelaide University suggested releasing rabbits inoculated with rabbit scab into an enclosed trial area.[30][31] Limited trials suggested that the measure would be ineffective in the drier parts of the continent.

In September 1887, Dr Herbert Butcher (1854–1893) of Wilcannia found a number of dead, emaciated rabbits at Tintinallogy Station. Dr H. Ellis of Sydney and he concluded that the animals had died of a novel disease, which they dubbed Tintinallogy virus. They felt it could be an effective control measure, but whatever the rabbits died from was never proved to be infectious or contagious. It may have been simple starvation caused by natural elements.[18]

In 1906 and 1907, Jean Danysz, of the Pasteur Institute of Paris, conducted trials on Broughton Island, New South Wales, of a strain of Pasteurella bacteria he had developed, which proved to be specific to rabbits, but it proved to be a less-than-satisfactory control measure. Dr Danysz felt that Broughton Island was a poor choice of test site, and that extensive experiments should be conducted on the mainland. Frank Tidswell, who was his chief Australian collaborator, continued Danysz's trials after he left in 1907, and also began trials of the Yalgogrin, Gundagai, and Picton microbes (named for the stations where infected rabbits were found), but financial support was lacking from the Federal government, or the collaboration of affected states, that would be necessary to prove that the measure safe and effective. The fact that these pathogens did not wipe out whole populations might have raised doubts as to their efficacy.[32]

In 1950, following research conducted by Frank Fenner, myxoma virus was deliberately released into the rabbit population, causing it to drop from an estimated 600 million[33] to around 100 million. Growing genetic resistance in the remaining rabbits had allowed the population to recover to 200–300 million by 1991.

To combat that trend, over three years from June 1991, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) comprehensively tested the potential of a Calicivirus, which causes rabbit haemorrhagic disease (RHD), for biological control of wild rabbits.[34] The virus escaped from a quarantine compound on Wardang Island, South Australia, where the field tests were being carried out, and by late October 1995, it was recorded in rabbits at Yunta and Gum Creek, in north-eastern South Australia.[35] By the winter of 1996, the virus was established in Victoria, New South Wales, the Northern Territory and Western Australia.[36] The virus was discovered in these areas by analyzing livers of dead rabbits. The success of the virus was found to be higher in dry areas, because of a benign calicivirus found in the colder, wetter areas of Australia, which was immunising rabbits against the more virulent form.[37]

A legal vaccine exists in Australia for RHD, but no cure is known for either myxomatosis or RHD, and many affected pets have to be euthanized. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus[38] developed in Spain.

A team headed by virologist Francisco Parra, working with the University of Oviedo, in Asturias, northern Spain, identified a new variant of the virus in 2012.[39] The pathogen, a new strain of K5 (RHDV1), is both extremely lethal and highly contagious.[40] In 2017, it was released by Australian authorities at around 600 points on the continent. Owners of domestic rabbits were advised to vaccinate their animals.[41]

In southern Europe, the scarcity of rabbits threatens the conservation of endangered predator species higher up the food chain, that depend on small game such as rabbits. These include the Iberian lynx and the Iberian imperial eagle. For this reason, biological warfare against rabbits in Australia is a serious concern for conservation activities in other parts of the world.[42]