Reproductive characteristics of feral pigs in New Zealand

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.