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. 1992. Reproductive characteristics of feral pigs in New Zealand. Acta theriol. 37: 259 -270.Breeding was studied in feral pigs Sus scrofa Linnaeus, 1758 inhabiting the northern part of the South Island, New Zealand. In a sample of 1,117 female pigs 50.4% showed evidence (pregnancy or lactation) that they were breeding. There was no statistically significant regional variation in the breeding status of females. Breeding occurred throughout the year with birth peaks in July-November and March. Among 101 females 5-8 months old, 30 (29.7%) were pregnant. The oldest breeding sow was 14 years old. Breeding females up to 17 months old were significantly heavier than non-breeding females, but the difference ceased to be significant for older animals. Pregnant females averaged 6.2 foetuses (range 1-11). Lactating females had on average 5.4 teats extended (range 1 -12). For areas where pigs are considered a pest species a simulation model predicted a population recovery time of 30 months from a 70% kill.

This study evaluates dental ageing techniques for feral pigs in northern South I., New Zealand. Ages of pigs were estimated by three techniques: tooth eruption and replacement on criteria calibrated from pen-reared American-bred European wild pigs; tooth eruption, development, and wear calibrated from known-age feral pigs from the study area; and annular growth in cementum of molariform teeth. All age estimations showed strong agreement with each other and with known ages. The eruption and replacement criteria were most useful for ageing pigs less than 30 months old, whereas the other two criteria were more suited to ageing pigs more than 30 months old. All permanent teeth of New Zealand feral pigs erupted 1-2 months earlier than in European and Malayan wild pigs, and permanent premolars erupted up to 4 months earlier than in Japanese wild pigs. Earlier eruption may reflect early onset of maturity in New Zealand pigs. The clarity of annuli observed varied between animals, but generally increased with age. Pigs from unforested habitat had a higher percentage of clearly defined annuli than those from forested habitat. This may be explained by a climatic or dietary factor.

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