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Rabbits

by  Robert Peden

Rabbits were introduced to New Zealand in the 19th century for food and sport. But they soon became a pest, reaching plague proportions in some areas. Rabbits have cost the country millions of dollars – through attempts to control them and lost production on farmland.


The spread of rabbits in New Zealand

Rabbit behaviour and habitat

The common European rabbit (Oryctolagus cuniculus) is native to Spain and Portugal, and has adapted to that region’s unpredictable Mediterranean climate. Rabbits are able to take advantage of good seasons and breed prolifically when food is available. They can also survive through extended droughts – even eating their faeces to absorb more nutrients. Rabbits are particularly well adapted to the drier parts of New Zealand, where survival rates of the young are high.

Rabbit or hare?

Hares and rabbits are lagomorphs and belong to the Leporidae family. Hares are generally bigger than rabbits. They have longer, black-tipped ears and live solitary lives. Rabbits live in social groups. Their young are born blind and without fur, and spend the first few days of their lives in a fur-lined nest, whereas baby hares can run within a few minutes of birth. Hares are a nuisance in some parts of New Zealand, but do not damage vegetation the way rabbits do.

Introducing rabbits to New Zealand

Rabbits were brought to New Zealand and released for both food and sport at various sites as early as the 1830s.

Rabbit plagues

Once rabbits became established, their population increased to plague proportions several times. The first rabbit plague began in the early 1870s and petered out about 1895. Another increase occurred in the early 1920s. There was a major irruption in the 1940s, and the most recent began in the late 1980s.

Impact of rabbit plagues

Rabbits have cost New Zealand many millions of dollars, through the direct cost of controlling them, and the loss of production from farms. Their impact on the drier areas of the South Island has been little short of an ecological disaster, as the vegetation grazed off by rabbits has never recovered. The worst affected areas – once well covered with tussock, grasses and small shrubs – now have very little vegetation cover, which has led to soil erosion by wind and rain. The loss of soil has left areas where only the hardiest colonising plants will now grow. Burrowing by rabbits in some soil types and on steep slopes has also led to soil erosion.

The South Island plague

Southland and Otago

A population of rabbits became established in the coastal sandhills between Invercargill and Riverton in the 1860s. In the early 1870s rabbits from this area began moving up the banks of the nearby rivers onto the inland plains. By 1875 they were established in Central Otago. By the early 1880s rabbits had spread to all parts of Otago and Southland and had begun to invade Canterbury. In the 1890s they overran the Mackenzie Country.

Marlborough

Rabbits were released inland from Blenheim in 1858 and again in 1865. In the early 1870s they spread up the Wairau and Awatere rivers into inland Marlborough. At the same time, silver-grey rabbits that had been released near Kaikōura about 1862 moved into the drier inland areas. By about 1887 both of these populations began encroaching on the Amuri district in North Canterbury.

Breeding like rabbits

A single female rabbit can have 45 offspring in a year, producing a litter of four or five kittens every six weeks. Rabbits can breed at five months of age, so a female born in early spring will produce young within the same breeding season. Rabbit populations commonly increase eight- to tenfold in one season.

South Island plague peak

In the South Island the first rabbit plague had peaked by 1895. After this, rabbit numbers remained high in the semi-arid region of Central Otago, but dropped markedly in other areas. Most of central Canterbury remained relatively free of the pest. However, in later rabbit irruptions the region did not escape so lightly.

The spread of rabbits in the North Island

The timing and dynamics of the rabbit plague in the North Island differed from the South Island. The extensive areas of forest and higher rainfall hindered their spread.

Rabbits were established in the Wairarapa by 1863, but an outbreak of coccidiosis (a parasitic intestinal disease) in the 1880s slowed their spread. However, by the beginning of the 20th century, large numbers had spread into Hawke’s Bay. They did not reach Taranaki and the far north in any number until about 1946.

In the North Island, rabbits have only been a major problem in Hawke’s Bay and parts of Wairarapa.


Rabbits’ impact on farming

Early impact on southern sheep stations

Rabbits caused a major drop in productivity on the early sheep stations, as they ate out the feed, leaving little for the sheep. At Kawarau Station near Cromwell, rabbiters took 244,000 rabbit skins in 1884 and 283,000 in 1885. Because of this infestation, the productivity of the station declined dramatically. The lambing percentage (number of lambs per ewe in a flock) fell from 70% before the rabbit influx to 45% in 1885, the death rate of the flock rose from 3.5% to 10.5%, and the wool cut per sheep dropped by 0.56 kilos.

Mt Nicholas Station, at Lake Wakatipu, carried 20,000 sheep through the 1870s, but rabbits ate out the feed and by 1888 the flock was reduced to 2,000. At the head of Lake Wakatipu John Butement had 37,000 sheep on North Station in 1880. Rabbits grazed out the vegetation where Butement wintered his flock, and in 1888 he was forced to drop his sheep numbers to 17,600. The following year he was bankrupted. The mortgagor could not find a purchaser for the leases, so they were abandoned.

Between 1877 and 1884, farmers gave up 75 runs in Otago because of the impact of rabbits. By 1887, 1,346,554 acres (545,000 hectares) had been abandoned in the province.

Parts of Canterbury escaped the worst of the first rabbit plague – but after the First World War stocking rates fell in some places in the same way as they had earlier in Otago and Southland. In 1917 W. Nosworthy took over Mesopotamia station, which had carried 23,000 sheep since about 1880. However, as the rabbit population grew, the flock was reduced to 5,000 by 1921.

Rabbit vs sheep

Ten rabbits eat as much feed as a 55-kilogram ewe. In 1880 the owner of Earnscleugh Station reckoned his run was infested with over 400,000 rabbits. Until then he had carried about 24,000 merino sheep, weighing about 36 kilograms each. The rabbit population on Earnscleugh equated to more than 66,000 sheep.

Cost of losses

Attempts have been made to put a dollar value on the cost of rabbits to the New Zealand economy. One estimate for 1995 was $14 million to $22 million for control and $8 million for loss of production. In 1999 annual production losses due to rabbits were estimated at $50 million.

These estimates ignore the cost to other resources, and the damage to the environment. Scientist G. Norbury has noted that ‘rabbits clearly impose significant costs to production, but there is no way at present to assess the marginal costs and benefits of rabbit control’. 1

Footnotes
  1. G. Norbury, ‘Advances in New Zealand mammalogy, 1990–2000: Lagomorphs.’ Journal of the Royal Society of New Zealand 31, no. 1 (March 2001): 87. › Back

Controlling rabbits with poison

Station owners and farmers tried a variety of measures to combat rabbits. At first they relied on the traditional methods of digging out burrows, hunting with dogs, shooting and trapping. Large gangs of men were employed, but were unable to cope with the vast numbers of rabbits.

Phosphorus and grain

Captain J. W. Raymond, who held Avondale Station in Southland, developed a recipe for poisoning wheat and oats with phosphorus. This became the favoured means for controlling rabbits in the 1880s and early 1890s. However, rabbits would not take the poison if grass was available, so it could only be used successfully in winter.

Phosphorised pollard (wheat bran), which was introduced from Australia in the mid-1890s, proved more palatable and rabbits took it year-round. Unfortunately stock also took the bait readily, so rabbiters had to be careful where they laid it. Despite that, phosphorised pollard was the most widely used measure of rabbit control in Otago and Southland by the end of the 1890s.

In a jam

Professional rabbiter W. H. McLean recalled a rabbit inspector telling him about a new type of bait in the 1930s:

‘D’you know they’re using jam as bait in the South Island? It started when a rabbiter heard a noise outside his camp one night; when he investigated he saw rabbits licking out jam tins. So he tried it as a bait and it worked. They like apple and raspberry jam best. Quince, too, but that’s a bit dear.’ 1

Other poisons

A range of proprietary poisons were marketed. Perhaps the most successful was Toxa. It required no mixing, it was easy to lay and rabbits took it readily. However, it was more expensive than other poisons. A variety of other options were also tried: arsenic and chaff, arsenic and grain, strychnine and apples or carrots, and strychnine and jam. The last was popular as it was easy to transport to hill country.

Poisonous gas

Rabbit burrows were also gassed with bisulphide of carbon. This was most effective in heavier soils, as the gas tended to dissipate in light or sandy country. There are reports of gas being used as early as 1879, but it did not become widespread until the early 20th century, when machines were invented to pump gas or to spray the liquid bisulphide directly into burrows.

Aerial poisoning and 1080

There was a major breakthrough in large-scale rabbit control after the Second World War. In 1949, experiments in dropping poisoned bait from fixed-wing aircraft proved successful. Remote and inaccessible areas, particularly in the South Island high country, could now be included in large-scale poisoning programmes.

In 1954 a trial found that sodium monofluoroacetate (1080) was more effective than other poisons previously used. By 1960 it had become the main poison used in rabbit control. The combination of aerial spreading and the use of carrots poisoned with 1080 enabled rabbit boards (which were responsible for rabbit destruction work) to reduce rabbit numbers in most areas by the early 1960s.

Footnotes
  1. W. H. McLean, Rabbits galore – on the other side of the fence. Wellington: Reed, 1996, p. 53. › Back

Rabbit fences

From the 1880s, farmers began building rabbit fences using wire netting. There were two distinct aims: to prevent rabbits spreading into new areas, and to contain them for better control.

The first major rabbit fence

The first officially approved rabbit fence was a 64-kilometre barrier to stop rabbits moving into Hawke’s Bay from northern Wairarapa. It was put up between 1882 and 1885, but failed to halt the spread.

Fenced off

Rabbits increased to alarming numbers on Brancepeth Station, east of Masterton, in the mid-1880s. Hugh Beetham, the owner, ring-fenced the 23,067-hectare property, then divided it into four using rabbit fences. The job involved about 112 kilometres of fencing. With his farm in rabbit-proof blocks, Beetham then used poison to get his rabbit problem under control.

Public rabbit fences

Three major rabbit fences were built in the South Island in the late 1880s. A 128-kilometre fence from Aoraki/Mt Cook to Kurow was put up between 1887 and 1891, to prevent rabbits from spreading to South Canterbury from Otago. In 1889 the Hurunui Rabbit Board built a fence on the south side of the Hurunui River to protect the district from a rabbit invasion from Marlborough. Two years later, the Amuri and Hurunui Rabbit Boards erected a 135-kilometre fence from the head of the Waiau River to the sea. But at best, these fences merely slowed the advancing horde.

Private rabbit fences

Several runholders put up a considerable amount of rabbit fencing on their properties. A notable example was on the Avondale run in northern Southland. Rowley and Hamilton took up the run after the previous leaseholder was forced off by rabbits, and ring-fenced the whole 10,521-hectare estate with rabbit netting. They were able to control the pests and prevent re-infestation. By 1886 they had increased their sheep flock from 7,000 to 18,000 – the number carried before rabbits became a nuisance.


Using predators for control

The natural enemy debate

Many pastoralists thought that ‘natural enemies’ (predators) would control rabbits more effectively than any other measure. New Zealand’s only native predators of rabbits were the swamp harrier (Circus approximans) and the weka (Gallirallus australis). Farmers saw mustelids – ferrets, stoats and weasels – as the most likely candidates, although others were considered.

There was a bitter debate in the 1880s about releasing mustelids. Some argued that they would have little effect in reducing the rabbit population, and would cause the extinction of ground-dwelling native birds. However, by the mid-1880s thousands had already been released. In fact, ferrets had official protection under the 1881 Rabbit Act as ‘natural enemies of the rabbit’.

Importing mustelids

Importing ferrets, stoats and weasels proved difficult – they were susceptible to distemper and many died in transit. In the early 1870s G. F. Bullen, a runholder from Kaikōura, shipped 600, all of which died. Of his next shipment of 700, only two ferrets and two weasels survived. In 1883, the government shipped 1,456 ferrets to New Zealand, but only 367 landed alive.

Despite the high death rates, importations continued through the 1880s. Government figures for 1884, 1885 and 1886 show that 18,333 ‘natural enemies’ were imported, but this was probably a conservative figure.

Mongoose on the loose

The introduction of a variety of predators for rabbit control was debated in the 1870s and 1880s. The American marten and the eagle were discussed, but not released. But a Kaikōura runholder released nine or ten mongooses in the mid-1870s, and the government let 16 loose in Southland in 1876. Other mongooses were liberated near Moa Flat in Otago. Fortunately, they did not acclimatise.

Breeding and releasing mustelids

Because shipping mustelids was difficult, the government and private individuals set up breeding stations. Richmond Brook and Flaxbourne stations in Marlborough bred and released about 800 ferrets a year in the 1880s. In 1888 the Amuri Rabbit Board liberated 1,000 stoats and weasels, 1,000 ferrets and 400 cats. The following year it released 600 stoats and weasels, 800 ferrets and 400 cats. In 1890 over 7,000 ferrets were released in Otago. A report in 1889 could not say how many had been released in Southland, because large numbers were bred and liberated privately.

A costly failure

From the 1870s to the turn of the 20th century, pastoralists and the Department of Agriculture enthusiastically supported using predators for rabbit control. However, opposition to the release of mustelids continued. In 1895 a columnist for the Otago Witness noted that ‘ferrets and weasels appear to be on the increase, but they do not as yet seem to have had much effect on the [rabbit] pest’. 1 Ten years later the same paper commented that ‘the ferret as a rabbit exterminator has been found of little value, while it is of much more harm in other directions’. 2 By then, mustelids had spread throughout the South Island.

Mustelids became a pest themselves, preying on native animals. Stoats in particular have had a devastating effect on native bird populations.

Footnotes
    • Otago Witness, 9 May 1895, p. 13. › Back
    • Otago Witness, 30 August 1905, p. 7. › Back

Commercialisation and control

Exporting rabbit skins

A commercial industry began with the first attempts to control rabbits. In 1873 over 36,000 rabbit skins were exported. In 1883 nearly 10 million were shipped to Britain, in 1893 just over 17 million were exported, and in 1924 the number of rabbit skin exports peaked at 20 million. Most were taken from poisoned rabbits where the carcass was of no value.

A golden egg?

The Liberal Government was opposed to rabbit trapping as a commercial venture. The minister of lands, John McKenzie, claimed that the ‘professional rabbiter will not kill the goose that lays the golden egg’ 1, while the secretary of agriculture, J. D. Ritchie, argued that if ‘the same energy were exercised in thoroughly poisoning the ground as in trapping, the results would be more permanent’. 2

Meat exports

Some entrepreneurs thought large-scale poisoning without using the carcasses was wasteful. They thought that exporting rabbit meat could be both a successful industry and a solution to the rabbit problem. In 1881 and 1890 meat-preserving plants were set up in Southland to can rabbit meat. The 1881 plant soon failed, and production from the other plants was so low as to have little impact on rabbit control. However, in 1894 25,000 frozen rabbit carcasses were exported to Britain. The business grew quickly, and 6.5 million carcasses were exported in 1900. Over 99% of this trade came from Otago and Southland.

Meat trade debate

Outside the far south, trapping for meat was seen as counter-productive to the aim of exterminating rabbits. Within Otago and Southland there was a bitter debate over the meat trade. Proponents claimed that rabbits could never be exterminated, but could be controlled by trapping and at the same time provide a valuable income for rural workers. Opponents of trapping for meat argued that ‘preserving rabbits preserved the rabbit’ 3 and that trappers would never kill all the rabbits and destroy their livelihoods. Despite the obvious failure of the meat and skin industries to control rabbits, the trade continued until 1956.

Footnotes
  1. Otago Witness, 10 March 1898, p. 5. › Back
  2. Otago Witness, 3 December 1898, p. 6. › Back
  3. Otago Witness, 1 November 1894, p. 18. › Back

The role of government

Rabbit Nuisance legislation

The first Rabbit Nuisance Act was passed in 1867, and there have been many more acts since. The 1881 Act established a system of rabbit inspectors, and the 1882 Act increased their powers. Inspectors came under the authority of the Department of Agriculture after it was set up in 1892. Rabbit control was one of the department’s major functions, accounting for a quarter of its budget in 1895.

Rabbit Nuisance Amendment Act 1947

By 1946, there were over 100 rabbit boards, administering rabbit control over 7.3 million hectares. The Rabbit Nuisance Amendment Act 1947 was a landmark in the attempt to control rabbits. It required all rabbit boards to adopt a ‘killer policy’ – their priority was to kill rabbits, almost regardless of cost. The Act restructured the rabbit control system:

  • It set up a central advisory body, the Rabbit Destruction Council, consisting of farmer and government representatives.
  • Rabbit board staff were made responsible for all organisation and operation of rabbit destruction.
  • Funding came from rates charged to landholders, based on the area of their properties or the number of stock carried. This was paid to locally elected rabbit boards.
  • Central government subsidised rates on a pound-for-pound basis.
  • Rabbits were to be progressively de-commercialised.

From state subsidies to user pays

The changes brought in by the 1947 Act, along with aerial poisoning and 1080 poison, were highly successful in controlling rabbits from the 1950s to the 1970s. But despite the drop in numbers, the cost of control remained high. In 1980 the government changed its funding from a dollar-for-dollar subsidy to a lump sum payment, to be reviewed annually. Then in 1984 a ‘user pays’ policy was adopted, and the government’s contribution was progressively withdrawn.

The administration of rabbit control was completely restructured in 1989. The newly formed regional councils took over the role of the Agricultural Pest Destruction Council (which had replaced the Rabbit Destruction Council in 1967) and rabbit boards were disbanded. Coincidentally, at the very time that funding for rabbit control declined and its administration changed, a long drought in Marlborough, Canterbury, and North and Central Otago led to an explosion in rabbit numbers.


Biological control

The call for myxomatosis

Myxomatosis (a viral disease of rabbits, caused by the myxoma virus) had been introduced to New Zealand in 1952, but failed to become established as there was no vector to spread it through the rabbit population.

In the 1980s there were changes in the funding and management of rabbit control, along with an outbreak of rabbits. Farmers in badly affected areas demanded new tools to control the pests. They urged the government to release myxomatosis again, but in a more controlled way so it would become established effectively.

The Parliamentary Commissioner for the Environment heard submissions in 1987, but found the risks of introducing the virus outweighed any advantages.

The Rabbit and Land Management Programme

Instead the government introduced the Rabbit and Land Management Programme. This assisted farmers in the most rabbit-prone parts of the South Island to make their properties rabbit-proof and their farms sustainable. The programme included rabbit control on a grand scale. Netting was supplied to secure farm boundaries, stopping rabbits invading from elsewhere, and containing them so they could be destroyed.

Farmers were also funded to improve their pastures, with the aim of strengthening farm finances so they would no longer need help to control rabbits after the programme finished. It was also a pest-control measure, as it was thought that rabbits did not thrive in areas with heavy vegetation cover.

The rabbit revival

The Rabbit and Land Management Programme ran from 1989 to 1995. Despite the outlay of $28 million by the government, regional councils and landowners, the gains were short-lived. The initial poisoning was highly successful, as were some of the land improvement efforts. But after a series of dry seasons rabbit numbers began to grow, and, in the user-pays environment, farmers faced expensive poisoning programmes to try to reduce numbers. At the same time another biological control appeared that landowners thought could offer a cheap, long-term solution.

Rabbit haemorrhagic disease (RHD)

Rabbit haemorrhagic disease (RHD), formerly known as rabbit calicivirus disease (RCD), was first reported in China in 1984. It soon spread through Asia, Europe and North Africa, killing millions of rabbits. In 1991 a laboratory trial of the disease began in Australia, and field trials began on Wardang Island off the Australian coast in March 1995. The virus soon spread beyond the perimeter of the testing site, and in October 1995 RHD was found on the Australian mainland.

RHD on the menu

The remarkable speed at which RHD spread through Central Otago and the Mackenzie Country was largely due to the actions of some farmers. They collected the internal organs – in particular the liver, heart and lungs – from rabbits that had died from RHD, minced them in kitchen blenders, covered bait with the diluted slurry and spread it over their farms.

Illegal release of RHD

In mid-1996 a group that included 10 regional councils lodged an application to the government for the release of RHD in New Zealand. In July 1997 the deputy director-general of agriculture declined the application. Some farmers responded by illegally releasing the disease. In late August RHD was found to be killing rabbits in the Cromwell area of Central Otago, and the disease quickly spread through the district and into the Mackenzie Country. It has since spread throughout New Zealand.

At first the disease was very effective in reducing rabbit numbers in most parts of the country. Vegetation recovered well, especially in the semi-arid areas of the Mackenzie basin and Central Otago. However, in 2007, rabbits were showing signs of becoming immune to RHD, and some farmers had to resort to poisoning. It is clear that in drier areas where rabbits thrive, the battle is far from over.


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How to cite this page: Robert Peden, 'Rabbits', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/rabbits/print (accessed 21 October 2017)

Story by Robert Peden, published 24 Nov 2008