New Zealand Journal of Ecology (1988) 11: 73- 78

Diet of Feral Pigs in the Podocarp-Tawa Forests of the Urewera Ranges

Research Article
C. Thomson  
C. N. Challies  
  1. Forestry Research Centre, Forest Research Institute, P.O. Box 31- 011, Christchurch, New Zealand

Samples of stomach contents were collected from 104 feral pigs (Sus scrofa) shot in the Urewera Ranges between December 1982 and June 1985. These were sorted into food items which were dried, weighed, and combined to give estimates of their annual and seasonal diets.
Overall 51.80/0 of the pigs' food was obtained by foraging on the ground, 30.6% by rooting, and 17.6% by browsing and grazing. Their annual diet comprised 71.9% plant material and 28.1% animal material, the proportions being similar in all seasons. The fruits of tawa (Beilschmiedia tawa), hinau (Elaeocarpus dentatus), and supplejack (Ripogonum scandens) together made up one-third of the pigs' diet. These were taken seasonally, comprising 60% of their food in autumn, 42% in winter, and 25% in summer. The other major plant foods were the roots of supplejack, the fronds and stems of tree ferns (Cyathea spp.), and the rhizomes and roots of bracken (Pteridium esculentum); the first two foods were taken mainly in spring and summer. Earthworms and vertebrate carrion, especially the carcasses of brushtail possums (Trichosurus vulpecula), were the main animal foods eaten.
It is suggested that periodic fluctuations in pig numbers may be associated with yearly differences in tawa and hinau fruiting.