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Environmental Damage By Wild Rabbits In Australia And New Zealand

by Commonwealth Scientific and Industrial
Research Organization (CSIRO)

WILD EUROPEAN RABBITS are Australia's most serious animal pest and New Zealand's second most serious (after the brushtail possum). Damage by wild rabbits in Australia, including the annual cost of control and production losses, has been estimated at $600 million.

The cost of wild rabbits is more than economic: they cause environmental damage which is often irreparable. The loss of vegetation from rabbit grazing threatens the survival of native birds, mammals, and insects that rely on plants for food and shelter. Rabbits have contributed to the extinction of many native plant and animal species.

Wild rabbits compete with livestock for available pasture and kill young trees and shrubs. Their warrens contribute to soil erosion by removing vegetation and disturbing soil.

In New Zealand wild rabbits have caused significant land degradation, particularly in the drier pastoral country of the South Island.

Wild rabbits and the environment

The impact of wild rabbits is particularly serious in dry inland areas where trees and shrubs do not germinate regularly. Rabbits are effective at finding and eating tree seedlings and shrubs. Where native species of trees are planted in farm afforestation programs, rabbits (even at low densities) can destroy up to 90 per cent of seedlings. Many species of arid-zone trees and shrubs are at risk of extinction unless rabbit numbers are permanently reduced to much lower levels.

Wild rabbits are implicated in the decline of many species of native animals. In the south-east of South Australia, the wombat population declined markedly once rabbits invaded the area. By increasing grazing pressure, rabbits have changed the types of feed available for wombats: adult wombats can cope, but not the young. The bilby (or the rabbit-eared bandicoot) was once common throughout southern Australia. We now know that bilbies usually disappear from an area within 10 years of rabbits arriving. The bilby is now endangered and only found in isolated areas of central Australia where rabbits are absent. Wild rabbits also affect native wildlife by supporting feral predators particularly the European fox.

Problems caused by rabbits often go unrecognized by the untrained eye until it is too late. Brian Cooke is Australia's leading rabbit ecologist. His article, 'Rabbits - Indefensible on any grounds' (Cooke 1991), emphasizes the impact of wild rabbits on Australia's environment.

  • In arid and semi-arid parts of Australia rabbits at a density of only one to two per hectare could find and eat all Acacia seedlings (Lange and Graham 1983).

  • For the mallee area, where rabbits at a density of little more than three per hectare were eliminated, all sheoaks Allocasuarina verticillata regenerated (Cooke 1987).

  • Rabbit densities of six to seven per hectare are common in arid zones.

  • Henzell (1988) estimated losses at $17.4 million annually in livestock production due to competition with rabbits in South Australia's arid zone.

David Lord, a primary producer in western New South Wales, can trace damage caused by wild rabbits and the enormous effort and cost involved in rabbit control through experience on his property, Thackaringa Station.

  • Rabbit populations of less than three per hectare can maintain the dominance of introduced plants. But when rabbits are excluded, native grasses can replace introduced species. (Annual species cannot withstand drought conditions, so they dry up and expose the soil to winds which can result in dust storms). Perennials are well adapted to the harsh environment but not the intense grazing pressure of the relentless and voracious appetite of rabbits. Perennials (bluebush and saltbush) are high in protein so are better for livestock.

  • In "Johnson's paddock" which has a carrying capacity of only 600 sheep 2,000 warrens have been ripped. The number of rabbits per warren vary from 10 to 50, depending on the amount of green feed available. The 2,000 warrens could therefore house 20,000 to 100,000 rabbits. Ten rabbits eat as much as one sheep, the equivalent of at least 2,000 sheep in just one paddock. That's bad news for the land.

  • Average warren density on Thackaringa is about one warren every 2.5 hectares. Even if only one rabbit lived in each warren, the population would be enough to prevent the regeneration of native seedlings.

  • There is a whole suite of plant species and dependent animals threatened with severe range-contraction or extinction. Rabbits make this problem worse.

  • The value of lost production due to rabbits is more than $115 million annually just for the wool industry in Australia. A new study now puts the total cost to the agricultural industry at around $600 million per year. This doesn't take into account environmental damage and the effects on the sustainability of future landuse.

  • Rabbits pressure native wildlife by competing for food, particularly under drought conditions.

  • Rabbits hinder the regeneration of native plant species. Rabbits eat more seedlings per year in Australia than could be planted in a decade of tree-planting. They also select the most nutritious parts of plants.

  • Rabbits can graze plants to ground level and eat roots, which sheep and cattle can't do because of their different grazing abilities.

  • Areas heavily grazed by rabbits can lose all perennial plant species like bluebush and salt-bush which can lead to woody weed invasion, pasture instability and reduced carrying capacity of the land.

  • Rabbits are implicated in the decline of many species of native animals. For example, there are 13 species of native animals known to be extinct in the Broken Hill region. According to Danielle Ayers of the National Parks and Wildlife Service, these include the western quoll, pig-footed bandicoot, golden bandicoot, western barred bandicoot, bilby, greater stick-nest rat, long-tailed hopping mouse, plains rat, long-haired rat, and probably burrowing bettong, brush-tailed bettong, eastern hare-wallaby and gould's mouse and another 22 species are now endangered.

  • The benefits to the land from reduced stocking rates will not be realised unless factors such as rabbits, woody weeds, and destruction of native animals and habitat by feral animals can be brought under control.

Rabbits in New Zealand

Rabbits occupy 55 per cent of New Zealand, from sea level to 2000 metres. In the drier tussock grasslands rabbits have denuded land causing soil erosion and loss of species. In other parts of New Zealand rabbits compete for pasture and impede the establishment of tree crops.

While predators, particularly ferrets, are an important means of rabbit control, they are also known to be infected with Tb (one of the country's greatest agricultural threats) in many areas. If it proves necessary to control ferrets to help reduce Tb in livestock, a significant increase in rabbit control will be required. The maintenance of ferret populations by rabbits also affects the conservation of native species, particularly ground nesting or burrowing species such as penguins.

Most rabbit control in New Zealand is by poisoning using aerial and ground applied baits (1080 and pindone) and shooting. In some areas rabbits now avoid baits and 1080 poison, reducing the effectiveness of these methods.

The cost of rabbit control remains high (over $20 per hectare in some areas) and all control costs are met by landholders. The national production losses and control costs are a minimum of $22 million annually.

Attempts to introduce myxomatosis to New Zealand in 1951/52 were unsuccessful. The failure of the disease to establish was probably due to a lack of biting insects which are an important means of transmitting the myxoma virus. An application to again release the myxoma virus (and rabbit flea) was made in 1993. This application was declined partly due to animal welfare concerns and because initial results of research on rabbit calicivirus in Australia were suggesting that it could be a more effective and humane biological control for wild rabbits.

Should you have a concern regarding the health of your Beagle(s), you should contact your veterinarian. All information on this site is presented solely for educational and informational purposes and should not, at any time, be considered a substitute for seeking or receiving veterinary care for your Beagle(s).