Rabbits occur in many parts of the Canterbury region. Their preferred habitat is grassland below an altitude of about 1000 metres, with free draining soils, sunny aspect, and less than 1000 millimetres annual rainfall. Their distribution and population density is reflected by a propensity of land to harbour populations of rabbits and the potential rate of population increase. Much of Canterbury lies in the low and negligible proneness classes with rabbits being present at low densities. In these areas, night-count levels are commonly below 10 rabbits per kilometre and rabbit densities are at 3 or below on the Modified McLean Scale. Higher numbers of rabbits are more likely to be found on high and extremely rabbit-prone land, especially in the absence of control.
Land use can also influence the occurrence of rabbits. For example, the change from tall tussock to short tussock or improved pastures has created an environment more suited to rabbits. Forestry, on the other hand, creates unsuitable habitat for rabbits once canopy closure is achieved, although forest margins and firebreaks can be problem areas. The introduction of Rabbit Haemorrhagic Disease (RHD) has had a dramatic effect on rabbit populations, particularly in the highly prone areas of the Waitaki and Mackenzie. In these two areas, rabbit levels are being maintained at very low levels, typically less than two rabbits per night-count kilometre. In most instances, the virus is capable of maintaining rabbit levels below Level 3 provided immunity levels do not develop.
In areas of high and extremely rabbit-prone land, population increase is not curbed by natural mechanisms and can quickly build to high levels. These areas occur largely in the Upper Waitaki Valley, Mackenzie Basin and the inland Kaikoura area. Moderately rabbit-prone land is an intermediate case, although in some situations rabbits can increase to high numbers. These lands occur mainly in the free-draining hill soil areas of North Canterbury and the foothills. Rabbits can cause a number of adverse effects particularly in the more rabbit-prone lands. At high numbers the control costs can be prohibitively expensive. Their impact reduces available grazing for domestic stock and subsequently decreases the financial returns to landowners and their ability to fund control. High rabbit numbers also assist in maintaining high predator numbers. This can lead to significant costs being incurred in situations where predators carry bovine tuberculosis. On highly rabbit-prone land, and to a lesser extent on moderately prone land, rabbits, often in conjunction with other grazing animals, cause a number of environmental effects, including:
Controlling high numbers of rabbits with poison can also lead to environmental effects. Prior to the arrival of RHD in 1997, the most effective tool for large-scale rabbit control was sodium monofluoroacetate (1080 poison), although other poisons such as 2-pivaloylindane-1, 3-indandione (pindone) were used. However, when the technical standards for the use of poisons are compromised, for example when it is used too frequently, rabbits can become reluctant to eat the poison (toxin aversion), or cautious about eating new things in their environment (neophobia). This results in the need for other more labour-intensive and costly techniques such as fumigation and shooting. Some people believe that the use of 1080 poison is undesirable for health and environmental reasons. Consequently, there is a continuing need to investigate, develop and implement new control tools, especially biological agents, so that the reliance on poisons is lessened or eliminated.
Environment Canterbury administers the RPMS (Regional Pest Management Strategy) which has a rule 7.4.5 (a) Land occupiers shall keep rabbit densities on the land that they occupy at or below Level 3 on the modified McLean Scale.
Environment Canterbury does not rate for or under take rabbit control itself. Our role is to monitor rabbit numbers and inspect land and issue notices where rabbits exceed level 3 on the modified McLean scale to ensure land owners meet their obligations to control their own rabbits.
Level 3 of the modified McLean scale is quite a lot of rabbits, (more than just half a dozen eating roses on a residential town boundary or digging holes in the garden). Those land owners who would still like to control rabbits below this scale are best to engage a rabbit control contractor or control them themselves if they can.
The vast majority of low land Canterbury does not have rabbit numbers at or above level 3 because the habitat, predation, disease (RHD & Coccidiosis) is not suitable to induce high numbers as they like dry, semi arid environments best.
Rabbit control went from Rabbit Boards' subsidised control in the 1980s to user pays.
Landholders wanting advice or assistance with rabbit control operations can use the services of Environment Canterbury's contracted rabbit co-ordinator, Steve Palmer (027 742 6126).
The rabbit co-ordinator position was established in October 2007 to provide landholders with advice on what is best practice technically and the most cost effective in terms of rabbit control, and to enable co-ordination of control operations where these straddle several land holdings and private and Crown land.
(03) 353 9007
0800 324 636 (EC INFO)
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