After their introduction, European rabbits soon became widely distributed throughout the drier regions of both main islands and on many offshore islands. As herbivores, they are very significant agricultural and ecological pests.
Rabbits thrive in dryland and semi-arid environments, especially in New Zealand’s South Island. They can populate these environments in destructive numbers if unmanaged. Reduction of populations is on-going and considered essential for the agricultural economic sustainability of New Zealand.
Rabbit facts
Domestic rabbits were commonly carried on sailing ships and sometimes released on islands as food for castaways. Rabbits were still imported as late as the 1860s to stimulate a domestic fur and meat trade. Establishment of wild populations was limited at first by lack of suitable habitat but increased pastoral farming assisted spread and growth in numbers. By the 1880s rabbits had become a serious threat to the fragile New Zealand economy.
Wild rabbits may live up to seven years but life spans are generally much shorter, with high rates of natural mortality among young animals.
Rabbits have a high capacity for reproduction and female rabbits (does) may be pregnant for 70% of a year. Early-born does may breed in their natal year. They can produce a total of 20 – 50 young per adult doe. Females are also capable of adjusting litter-sizes to food supply, so rabbit populations are capable of rebounding quickly from natural events or management actions.
Why rabbits are a problem
Rabbits are regarded primarily as an agricultural pest. They compete very effectively with livestock for pasture. On average, 7-10 rabbits consume as much as one ewe.
Rabbits also provide a stable food source for ferrets, a known carrier of bovine tuberculosis. Burrowing and scrapes cause extensive damage on erosion-prone soils, so much so that agricultural land can be rendered useless. Historically, some rabbit-infested farms were abandoned because owners could not make a living.
Rabbits also threaten ecological values where they browse on vulnerable native plant communities, and where as year-round prey they support the mammalian predators which are contributing to the decline of many New Zealand native birds and animals.
Managing rabbits
Early attempts to manage rabbit plagues inflicted on New Zealand one of our worst conservation disasters – the introduction of stoats, ferrets and weasels. These natural predators of rabbits rarely managed rabbit numbers effectively, and they have been disastrous for our native terrestrial species.
Historically, substantial government investments have been made to manage rabbits through other means: trapping, shooting, poisoning, gassing, burrow-ripping, pathogens and dogs. Myxomatosis was introduced in the early 1950s as a form of pathogenic control though, unlike Australia, it failed to establish through lack of a suitable spreading organism.
Today, landowners, including the Crown, are responsible for managing rabbits on their own lands. Regional councils monitor numbers regularly and may enforce rabbit management when numbers exceed agreed limits, regardless of land tenure.
Rabbit haemorragic disease (RHD) was introduced illegally in 1997. During the 2000s and early 2010s, field evidence showed that this initial strain had a reduction in potency and management effectiveness. A new strain of RHD (RHDV1-K5) was approved for release by the Ministry for Primary Industries in late 2017. This strain was released in mid-2018 by a national consortium of agencies with the aim of reducing wild rabbit populations. Local rabbit management is especially effective if landowners pursue survivors with shooting or poisoning.