The European rabbit (Oryctolagus cuniculus) was introduced into New Zealand in the mid 1800s, spread rapidly and soon began to seriously affect agriculture and natural ecosystems; it was quickly realised that rabbits had become a pest animal.
Mustelids and cats were brought in to contain the increasing populations but had little impact. Poisoning, trapping and shooting were widely used to attempt to control the rabbit pest but it was not until the de-commercialisation of rabbit carcases, and the establishment of rabbit boards in 1947, that effective rabbit control was achieved.
This intensification of control, particularly the use of aerial applications of sodium monofluroacetate (1080) from 1953, together with extensive land development, saw a rapid and large reduction in rabbit numbers throughout NZ. This early success gave control authorities the belief that eradication of the rabbit was possible.
Intensive secondary control, mainly in the form of night-shooting, was used throughout NZ with this goal. An attempt to establish myxomatosis in the early 1950′s was unsuccessful due to the absence of a suitable vector.
By the 1960′s, scientists were questioning the practicality of the eradication policy and the need for such costly approaches over much of New Zealand. A policy of ‘control’ was then introduced and efforts towards the control of rabbits became focused on the semiarid lands of the South Island. Here rabbits remained a major problem and this was putting a heavy financial burden on landholders, despite very significant Government financial assistance (up to 80% of control costs).
Financial reform coincided with structural reorganisation. The dollar-for-dollar rates subsidy on pest destruction work was replaced in 1981 with a block grant and in 1984 the Labour government accepted the proposal in the James Report to progressively introduce a user pays approach to pest destruction - over a ten year period. As part of this policy, the $7 million block grant was to be progressively reduced by $0.8 million per annum (Trost, pers. comm.).
By the 1980s, much of the land was being poisoned regularly but this approach encouraged the development of bait avoidance (neophobia) and poison shyness; kill rates dropped well below those achieved in the early days of 1080 use. In 1985, an application to the Government for the re-introduction of myxomatosis was declined. However, recognising that rabbits were a serious problem in semi-arid areas, the Parliamentary Commissioner for the Environment recommended the establishment of a Task Force in 1987 to address the problem through the development of integrated land management strategies. In 1988 the Ministers of Agriculture and Environment commissioned the Rabbit and Land Management Task Force to develop an integrated land management strategy. In September 1988 The Task Force recommended:
- that the Government continue to invest in rabbit management, primarily for resource conservation, but also as partial compensation for the denial of myxomatosis;
- that this investment be concentrated on the approximately 280,000 ha of highly rabbit prone land in the dry tussock grasslands;
- that the cornerstone of future rabbit and land management in the semi-arid regions should be a property plan;
- that research on the interactions between land type, land use and natural rabbit control agents (biological controls), particularly predators, must be intensified; and
- that funding for the programme to be via local government under new contractual arrangements.
These recommendations formed the basis of the Rabbit and Land Management
Programme (RLMP) that became operational with the establishment of regional councils in November 1989. The overall goal of the RLMP was to improve the long-term sustainability of land resources and ultimately of rural communities in rabbit prone areas.
Operationally, it consisted of:
- a grant (for rabbit control, fencing and habitat modification);
- a property planning programme, managed by regional councils; and
- a research, monitoring and facilitation/information exchange programme, managed by MAF.
The whole programme was guided by an advisory committee whose members were drawn from all key stakeholder groups. This committee was responsible for developing all programme policy. The $28 million programme ran from 1989 to 1995 with funding from central government, local authorities (regional councils) and participating landholders. The 115 properties that participated in the RLMP were selected according to their rabbit proneness and comprised 275,000 hectares of the semi-arid, rabbit prone lands of the South Island high country (RLMP News, October 1989).
There were 53 Otago properties in the programme, 37 from Canterbury and 5 from Marlborough. The significant rabbit problems in New Zealand are still largely confined to the semi-arid lands so these areas are the focus of this report. Table 1 shows the overall distribution of rabbit proneness categories across the whole of New Zealand. One of the aims of the programme was to reduce rabbit numbers to low levels and to leave the participating properties in a financial position that would enable them to economically sustain the control work required to maintain rabbits at these low levels (RLMP News, December 1991).
This aim was achieved on some properties, but others still had significant areas with rabbits at moderate to high levels at the end of the programme. Many properties were still struggling economically because of poor farming returns at the time. Rabbit populations continued to increase, with landholders poisoning as much of their affected land as they could afford (RLMP News March 1995 - Awatere Valley Field Day Report). In most cases the inputs of the programme such as rabbit proof fences still provided essential help in addressing the problem.
In 1989, while the RLMP was in operation, a joint research programme between NZ and Australia began to assess the possible use of a calicivirus as a biocontrol for feral rabbits. While field evaluations were being carried out in 1995 on Wardang Island off the South Australian coast, the virus escaped onto the mainland.
Initially, New Zealand and Australian authorities referred to the disease it caused as ‘rabbit calicivirus disease’ (RCD), but subsequently they adopted the internationally recognised name of rabbit haemorrhagic disease (RHD) The RCD Applicant Group, Chaired by Graeme Martin (Chief Executive of the Otago Regional Council) was then formed in New Zealand, comprising representatives from the Hawke’s Bay, Canterbury, Otago and Southland Regional Councils, Marlborough District Council, the Commissioner of Crown Lands and Federated Farmers of New Zealand (RCD Applicant Group, 1996).
In Australia, the virus proved to be very effective, decimating rabbit populations in the drier south-eastern parts of the country. Research on the virus pertinent to the NZ situation continued. Many landholders now saw the virus as the only solution to their high rabbit numbers. The Applicant Group first undertook a thorough assessment of the potential biocontrol, taking advice from experts in Australia, USA and the UK and a virology expert panel formed for the purpose.
Then, in 1996, it submitted an application to the Director General of Agriculture to import the virus comprising several hundred pages of review and conclusions and a further seven hundred and fifty pages of reference material (RCD Applicant Group, 1996). The decision to reject the application was called into question by the Prime Minister, the Minister of Agriculture, farming leaders and many others and the illegal introduction of RHDV into New Zealand in 1997 was subsequently acknowledged by the decision-maker as ‘probably an inevitable consequence’ of that decision (O’Hara, 2006).
Although it was present in the Mackenzie Basin in June of that year, it was not until the autopsies of dead rabbits collected near Cromwell in August that the presence of RHDV was confirmed. MAF attempted to contain the outbreak and advised that any persons in the possession of virus material would face harsh penalties. This did not deter some landholders from promoting the spread of the virus by collecting dead rabbits and spreading them on their farms and even using planes to drop them onto new areas. Livers, hearts and lungs of dead rabbits were pureed in food processors with water and the resulting solution, referred to as home brew (and even rabbit smoothie), was strained and sprayed onto baits such as oats and carrots. The baits were aerially or ground spread onto rabbit infested areas.
After the MAF announcement that it was no longer illegal to be in possession of the virus, many other landholders actively engaged in spreading the virus onto their properties. Virologists warned that the home brew method risked inoculating rather than killing rabbits. Following the RHDV introduction, there was an immediate and dramatic decline in rabbit populations with reductions at monitored properties varying from less than 20 percent to 90 percent (Lough, 1998).
However since the mid 2000′s, rabbit densities have increased on some properties and serological testing has shown that increasing proportions of live rabbits have been exposed to the virus and survived (ECan and Otago Regional Council reports).
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