Page 1 – 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.
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.
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.