Rabbits in Australia

From Wikipedia, the free encyclopedia

A European Rabbit on an Australian farm

In Australia, rabbits are the most serious mammalian pests, an invasive species whose destruction of habitats is responsible for the extinction or major decline of many native animals such as the Western Quoll. Annually, European Rabbits cause millions of dollars of damage to crops.

1 Effects on Australia's ecology
2 Introduction of rabbits to Australia
3 Control measures
- 3.1 Conventional control measures
- 3.2 Biological measures
4 See also
5 References
6 External links

[edit] Effects on Australia's ecology

An erosion gully in South Australia caused by rabbits.

The effect of rabbits on the ecology of Australia has been devastating. Since the arrival of Europeans in the 18th century, one eighth of all mammalian species in Australia have become extinct^{[citation needed]}. Rabbits are suspected of being the most significant known factor in species loss in Australia. The loss of plant species is unknown at this time. Rabbits often kill young trees in orchards, forests and on properties by ringbarking them.^[1]

Rabbits are also responsible for serious erosion problems as they eat native plants which leave the topsoil exposed and vulnerable to sheet, gully and wind erosion. The removal of this topsoil is devastating to the land as it takes many hundreds of years to regenerate. Some of this erosion may also be the result of settlers clearing much of Australia's land for farming (and use of unsuitable agricultural techniques) and to make room for housing.

[edit] Introduction of rabbits to Australia

Rabbits were first introduced to Australia by the First Fleet in 1788, but the current infestation appears to have originated with the release of 24 wild rabbits by Thomas Austin on his property, Barwon Park, near Winchelsea, Victoria, in October 1859 for hunting purposes. While living in England, Austin had been an avid hunter, regularly dedicating his weekends to rabbit shooting. Upon arriving in Australia, which had no native rabbit population, Austin asked his nephew in England to send him 24 grey rabbits, five hares, 72 partridges and some sparrows so that he could continue his hobby in Australia by creating a local population of the species. Many other farms released their rabbits into the wild after Austin. At the time he had stated, "The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting."^[2]

Rabbits are extremely prolific creatures, and spread rapidly across the southern parts of the country. Australia had ideal conditions for a rabbit population explosion. With mild winters, rabbits were able to breed the entire year. With widespread farming, areas that may have been desert, scrub, or woodlands were instead turned into vast areas with low vegetations, creating ideal habitat for rabbits. Humans are directly responsible for the initial release of the rabbits, and indirectly responsible for modifying the Australian landscape for ideal rabbit survival.

In a classic example of unintended consequences, within ten years of the introduction in 1859, the original 24 rabbits had multiplied so much that two million could be shot or trapped annually without having any noticeable effect on the population. It was the fastest spread ever recorded of any mammal anywhere in the world. Today rabbits are entrenched in the southern and central areas of the country, with scattered populations in the northern deserts.

Although the rabbit is a notorious pest it proved helpful to many people during the Great Depression and during wartime. Trapping rabbits helped farmers and stationhands by providing something to eat, extra income and in some cases helped pay off farming debts. Rabbits were fed to working dogs, and boiled to be fed to the poultry. Later, frozen rabbit carcases were traded locally and exported. Pelts too, were used in the fur trade and are still used in the felt-hat industry.^[3]

[edit] Control measures

A Royal Commission was held to the investigate the situation in 1901. Once the problem was understood, various control methods were tried to limit the population of rabbits in Australia. These methods had limited success until the introduction of biological control methods in the later half of the 20th century.

[edit] Conventional control measures

A load of rabbit skins, Northern Tablelands, New South Wales

Shooting rabbits is one of the most common control methods. However, this has little noticeable effect on rabbit populations.

Destroying warrens through ripping, 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 also often used. Poisoning is probably the most widely-used of the conventional techniques, as it requires the least effort. The disadvantage is that the rabbit cannot be used as food for either humans or pets afterward.

Another technique used occasionally is hunting using ferrets, where ferrets are deployed to chase the rabbits out to be shot or into nets set over the burrows. Since ferrets are limited in the number of rabbits they can kill, this is more a hunting activity than a serious control method.

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.

In 1907, the rabbit-proof fence was built in Western Australia, between Cape Keraudren and Esperance to try to control the rabbit population. European rabbits can both jump very high and burrow underground. Even assuming a perfectly intact fence stretching for hundreds of miles, and assuming that ranchers or farmers do not leave gates open for livestock or machinery, it was unlikely to be a success.

[edit] Biological measures

Releasing rabbit-borne diseases has proven somewhat successful in controlling the population of rabbits in Australia. In 1950, after research carried out by Frank Fenner, Myxomatosis was deliberately released into the rabbit population, causing it to drop from an estimated 600 million to around 100 million. Genetic resistance in the remaining rabbits allowed the population to recover to 200-300 million by 1991.

To combat this trend, Commonwealth Scientific and Industrial Research Organization (CSIRO) scientists released calicivirus (also known as Rabbit Hemorrhagic Disease or RHD) in 1996. However, the large number of rabbits killed resulted in starvation among their predators. The success of the virus was found to be higher in drier climates. This was because it appears there is another calicivirus in the colder, wetter areas of Australia, and that this virus was immunising rabbits against the more virulent form.

The Australian Government refuses to legalise a vaccine to protect pet rabbits against Myxomatosis, for fear the rabbit may escape and transmit resistance to the disease^{[citation needed]}. A legal vaccine exists in Australia for RHD. Thousands of pet rabbit owners in Australia suffer losses of their pet rabbits each year.^{[citation needed]} There is no cure for either Myxomatosis or RHD, and many affected pets are euthanised. In Europe, where rabbits are farmed on a large scale, they are protected against myxomatosis and calicivirus with a genetically modified virus.^[4] The virus was developed in Spain, and is beneficial to rabbit farmers. If it were to make its way into wild populations in areas such as Australia, this could create a population boom.