Rabbits and biological control: two unexpected Christmas presents

Domesticated rabbits arrived in Australia with the first fleet and some became established as feral populations around colonial settlements as early as the 1830s. However, the situation changed dramatically on Christmas Day 1859 when a dozen wild rabbits from the Liverpool area arrived in Port Phillip…

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One of the worst Christmas presents Australia has had. Richard Taylor

Domesticated rabbits arrived in Australia with the first fleet and some became established as feral populations around colonial settlements as early as the 1830s. However, the situation changed dramatically on Christmas Day 1859 when a dozen wild rabbits from the Liverpool area arrived in Port Phillip Bay aboard the brig Lightning.

Those rabbits were taken to “Barwon Park” (near Winchelsea Victoria) and carefully nurtured with the aim of having a new hunting resource. The introduction exceeded all expectations. When Prince Alfred, Duke of Edinburgh, visited in 1867 he shot 416 rabbits in a little over four hours.

As the rabbits spread beyond the limits of Barwon Park, consternation grew. Livestock production on some pastoral lands fell as much as 60% as the rabbits spread. Ways to control them became imperative.

The construction of rabbit-proof fences in Western Australia ranked among the more heroic attempts to stop the spread. The first fence took six years to complete and was eventually 1833km long. But it proved useless because rabbits were soon abundant on both sides. Two additional fences to the west were equally ineffective.

Although a whole arsenal of control methods was developed, including poisoning, barrier fencing, warren destruction and fumigation, few landholders persisted resolutely enough to keep rabbits out. Many used quick-acting poisons like strychnine-laced grain so they could collect the rabbits to skin and gain a little money to offset foregone livestock production. This had terrible consequences for native wildlife and did nothing to solve the chronic rabbit problem.

Most interestingly, some people in the colonies were considering far more advanced answers to the problem. In 1890 an inter-colonial Commission, including New Zealand representatives, offered £25,000 for anyone who could provide a solution.

It was an enormous amount of money for the time. Even the great Louis Pasteur responded by dispatching Adrienne Loire to Australia armed with vials of chicken cholera bacteria (Pasturella multocida). But, although lethal, the bacteria did not spread from rabbit to rabbit and so fell short of solving to the problem.

WA’s rabbit-proof fence was a lot of work for not much result. Laurence Norah

Even so, the concept of a biological control agent for rabbits had been firmly established. When Dr de Beaurepaire Aragào suggested from Uruguay in 1919 that a myxoma virus from the South American brush rabbit offered another possibility, the idea was immediately promoted. But field experiments, begun in the 1930s after much debate, indicated little likelihood of success. World War II also interrupted the work and 1950 saw what might have been the last of a series of investigations in the New South Wales Riverina area. Disappointingly, the disease spread slowly then apparently ground to a stop as summer approached. The researchers left to spend Christmas with their families.

Nonetheless, that was by no means the end of the story. CSIRO’s Bernard (Bunny) Fennessy, who worked on the project, once told me that his Christmas break in Melbourne was suddenly disrupted by a telegram requesting him to quickly return to the Riverina because rabbits were reportedly dying in huge numbers. Indeed it was true. Mosquitoes, unusually common owing to heavy rains, had carried the disease well beyond the experimental sites. The results were astounding. The numbers of rabbits fell by over 90%, and Australia’s rabbit problem seemed resolved overnight.

Over time, however, rabbits developed some disease resistance. As numbers increased landholders had to do more poisoning and warren ripping. This also stimulated further research work, resulting in the introduction of rabbit fleas to better carry the virus, then the release of a calicivirus (Rabbit Haemorrhagic Disease Virus or RHDV) to maintain a high level of rabbit control.

Awareness of the rabbits’ environmental impacts, previously badly neglected, was also growing. We now know that rabbits are degrading and seriously inhibiting the regeneration of many natural ecosystems. Rabbit browsing is a major threat to the regeneration of endangered buloke-pine woodland in north-western Victoria. Rabbits need to be kept at less than one rabbit to two hectares if seedlings are to survive and replenish the ageing tree population.

Fortunately, with advances in rabbit control we can ensure that rabbits are effectively managed and environmental goals can be met. The big surprise, however, is that conservation often requires a far higher level of rabbit control than the prevention of economic losses in livestock production.

Casting back to Christmas Day in 1859, it has been a long battle to retrieve the situation and make major gains against the rabbit. Our viral Christmas present of 1950 provided the turning point. Economically, Australia’s meat and wool industries have benefited to the equivalent of $70 billion (2011 A$) since then and we are in a good position to reduce rabbit impact in conservation areas. However, we cannot become complacent and on-going work is needed to maintain those advantages.

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9 Comments sorted by

  1. Chris Owens

    Professional

    Nice work on the rabbits. Why no similar programs for the cat & fox?

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    1. Sebastian Poeckes

      Retired

      In reply to Chris Owens

      Is the rumor true that in the 1970s or '80s a CSIRO program on developing diseases to control feral dogs and cats was terminated due to political pressure? The story that went around was that there were fears of the potential political backlash if such controls impacted on domestic companion animals.

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    2. John Holmes

      Agronomist - semi retired consultant

      In reply to Chris Owens

      In some of the discussions I was in; weeds were my specialty, but from time to time the similar issues of managing feral animals were discussed along with the issues of managing feral weeds. One case - buffaloes carrying water weeds from water hole to water hole, does it happen?

      If we develop a novel biological control agent for the fox,cat or even the rabbit, and that gets to Eurasia where these animals are endemic, would we be guilty of ecological vandalism? Brier Fox is quite an item of folklore in some parts and that does get in the way of managing control work here.

      I understood that this was an issue which slowed up the consideration of such work.

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  3. Brian Cooke

    Adjunct Associate Professor at University of Canberra

    Chris and Sebastian,
    Certainly there have been investigations into the possibility of controlling foxes and cats using some form of biological control agent but, in the case of foxes for instance, likely agents also affected dogs. Diseases that affect feral cats also spread through domestic cats. In such cases scientists generally make a political judgement of their own to discontinue work because it would be unlikely to get widespread community support. I also know of one additional bio-control…

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    1. Chris Owens

      Professional

      In reply to Brian Cooke

      Thanks Brian & Sebastian. I think a vaccine program for domestic animals would be one option. I understand the political realities and in particular the lack of political will and indeed regard for our native wildlife with neoliberal philosophy so prevalent.

      With foxes now established in Tasmania and the reported loss of small to medium sized animals across the country, I suspect we are about to witness another wave of extinctions in the absence of radical ideas and action.

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    2. Belal Haniffa

      Medical Student

      In reply to Brian Cooke

      "Diseases that affect feral cats also spread through domestic cats."

      Diseases that affect feral rabbits also affect domestic rabbits, and as far as I understand the myxoma vaccine is not made available to pet owners. I have lost pet rabbits to myxomatosis but I can understand the necessity of it. I think cat owners should have to do the same. Cats really have no place here either, especially the ones that are let outdoors.

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  4. Brian Cooke

    Adjunct Associate Professor at University of Canberra

    John,
    The issue of biological control agents getting into the wrong animal populations has been strongly debated over the years. The issue came to a head when Australia was trying to genetically engineer an immuno-contraceptive virus to reduce rabbits numbers while at the same time Spanish scientists were creating a live-virus vaccine that immunized rabbits against both myxoma virus and Rabbit Haemorrhagic Disease (RHD). Quite clearly, if either agent got into the wrong rabbit population it could…

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    1. John Holmes

      Agronomist - semi retired consultant

      In reply to Brian Cooke

      Thanks for filling in the details. These are debates that need to continue, and just not at the level of managing feral animals, or feral plants which may be useful crops else where. Any use in weapon systems needs to be monitored very carefully.

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