Until 1769, pigs were absent from New Zealand. According to Carl Walrond’s hunting article in New Zealand’s Encyclopedia, Te Ara, there were no land mammals in New Zealand other than bats before the arrival of introduced species. The French explorer Jean François Marie de Surville brought pigs to the country.
De Surville presented two pigs to Māori in Doubtless Bay in 1769, according to Hazel Petrie’s Te Ara article on introduced foods. Petrie explains that Māori quickly adapted to foods introduced by Europeans and shared the animals they received with other tribes. However, Walrond notes that what happened to the first pigs is unknown. Pigs later reproduced, and some escaped to establish feral populations. These feral pigs became known as Captain Cookers, although Petrie notes that at least some wild pigs in the South Island may have originated from Captain Cook’s voyages.
Gift turns into currency
More pigs arrived. Governor Philip King of Norfolk Island gave 12 pigs to Tukitahua, one of two chiefs who had been taken to the island. King also established a connection with another northern chief, Te Pahi, and arranged for 56 pigs to be transported to him on three ships between 1804 and 1805. Pigs soon became valuable trading goods. From 1805, Māori traded pigs with Europeans, and Te Ara notes that in the 1840s, a horse cost 40 pigs, while one schooner cost Bay of Plenty Māori 500 pigs.
Feral herds emerged alongside the trade. According to Walrond, wild pigs had become well established by 1840 and were the first introduced animals to be hunted for sport. In the late 19th century, Australians referred to New Zealand as the “Pig Islands” because of the prevalence of pigs. Hunting continued, and Te Ara’s broader history of hunting recognizes at least 25,000 pig hunters in the country.
How pigs affected the forest
In a 2015 study published in the New Zealand Journal of Ecology, researchers led by John Parkes spent 25 months studying soil, seedlings and the stomach contents of 14 pigs killed by hunters in Waitutu Forest in South Fiordland. Pigs overturned 7.4% to 12.4% of the soil in the forest terraces at any given time. The animals also returned to the same areas repeatedly, digging up older disturbed areas about seven times more often than newly disturbed areas. Stag beetles were the main target of their digging and made up 27% of the pigs’ food.
The team expected to find clear ecological harm but did not. Seedlings in dug-up patches were shorter, but the authors attributed this to pigs selecting those areas rather than to digging stunting the seedlings. Seedling numbers increased at similar rates in dug and undisturbed plots over two years, and most measures of soil microbes showed no significant differences. Parkes and colleagues concluded that the effects on seedling regeneration and soil life were limited or neutral, and that pigs probably had less influence on the forest than other invasive herbivores such as red deer.
That does not mean pigs have no ecological effects. The study did not determine how ground disturbance and predation affected populations of animals the pigs preyed on, such as stag beetles, and said those effects required further investigation. Five other stag beetle species are listed as nationally critical or nationally endangered, while earlier studies have suggested that pigs threaten some native invertebrates, including Powelliphanta snails. The paper said more research would be needed to assess whether those impacts justify controlling pig numbers.
The name “Pig Islands” reflects the prevalence of wild pigs in New Zealand, but the Waitutu study shows that their effects can vary by ecosystem. At the site studied, pigs disturbed forest soil and preyed on native animals, while their effects on seedling regeneration and soil life were limited, leaving their wider ecological impact for further study.
