The Nature of Wild Pigs

Forest and Bird, Issue 313, 1 August 2004, Page 23

The Nature of Wild Pigs

innaeus gave the name Sus scrofa to both the European wild boar and to its distant descendants, the domesticated pigs. Some authorities regard the domesticated form as a separate species and call it Sus domesticus, but the prevailing opinion is that they are one and the same. Of all members of the pig family, Sus scrofa occupies the largest range. Wild pigs originally occurred in Europe, Asia, North Africa and the Malay Archipelago until humans domesticated them around 5000 years ago and spread them about the world. Domesticated pigs were already a part of Polynesian culture 1000 years ago, but it seems they did not accompany the navigators on, or at least did not survive, their first voyage to New Zealand. The first pigs to arrive here were brought by the French explorer De Surville in 1769, who presented two to Maori in Doubtless Bay in Northland. Their fate is unknown but they are not credited with founding any feral population. During his second and third voyages to New Zealand in the 1770s, James Cook made

frequent gifts of pigs to Maori. He also liberated pairs, brought from the Society Islands and Tonga, around the Marlborough Sounds. Sealers and whalers liberally sprinkled pigs about the offshore islands as potential food for castaways; they were liberated on Auckland Island in 1807, on Raoul and Macaulay in 1836 and on Enderby and Campbell in 1867. By 1840 pigs were well established, but there is no evidence that any true ‘wild boars’ were ever introduced, although today’s feral pigs look very similar to them. Local populations were established from a mix of breeds and have since crossbred with others. For example, the ancestry of feral pigs in central Otago has been traced to the Tamworth breed, with small dashes of Berkshire and Hampshire breeds. Pigs are now found in most areas of New Zealand in a wide variety of habitats, from high alpine regions to lowland exotic forests. Colour patterns vary considerably within and between regions. Most commonly wild pigs are black, but other forms include rusty

red or ginger, sandy brown with black spots, a brown and white, white, black with a white stripe, grey, and a smoky blue, particularly in North Canterbury. Feral pigs are omnivorous, opportunistic feeders, and their feeding habits differ markedly from other introduced hooved animals, such as deer. Studies have shown that 62 percent of food is foraged on the ground, 31 percent by rooting, and the balance by browsing and grazing. Some 70 percent of their diet is plant matter — ferns, roots, fruits and crops — with animal carrion, earthworms, snails and insects making up the rest. Pigs typically forage on dusk. They can leave extensive damage with their specially adapted snouts and tusks. Adult boars have been known to weigh 350 kilograms (some domestic pig breeds can reach 450 kilograms), and reach shoulder heights of nearly a metre. Sows are slightly smaller, and while both sexes grow tusks, boars are able to sharpen theirs by rubbing the lower ones against the upper ones. These are used as weapons in often-violent fights between rivals for females. Boars are insulated with thick tissue around the front of the belly to help protect against the stab wounds they suffer in these contests. A male might secure as many as eight sows in a single season. In New Zealand, sows give birth to one litter in the spring, usually producing between 6 and 10 piglets. But mortality is high — perhaps half a litter will survive. Feral pigs are not protected by law in New Zealand and are classed as a ‘containment pest animal’ in most regional pestmanagement strategies under the Wild Animal Control Act 1977. As such, it is an offence to release pigs into the wild or carry out an act that will cause an increase in the population of feral pigs.