Feral pigs (Sus scrofa) are a threat to New Zealand’s biodiversity. Predation of frog species by feral pigs is a notable problem in other countries where pigs have been introduced. Our study aimed to determine through analysis of stomach contents if feral pigs are consuming frogs in the Waitakere Ranges, Auckland. Auckland Council contract pig hunters collected 274 feral pig stomach samples. Of these samples, 184 were screened for frog consumption via both dissecting microscope and DNA analyses.
While studying the population of feral goats (Capra hircus L.) on the northern tip of main Auckland Island in summer 1972-73 (Rudge and Campbell, 1975) skeletons were looked for from which to estimate natural mortality. We found only two skulls, both without horns or lower jaws, and concluded that goat bodies were eaten by feral pigs. Some pig faeces were therefore collected around Port Ross, preserved in 10% formalin, and later washed apart on a I mm sieve. Identifiable items were listed as present or absent and scored by percent frequency of occurrence.
Seven feral pigs (Sus scrofa), radio-tracked in relatively undisturbed rough pasture and forest near Murchison, New Zealand, for periods of 18-186 days, occupied home ranges of 28-209 ha. The immature pigs were significantly more active and had significantly larger home ranges than the adults, particularly adult females. The pigs were mainly nocturnal but they varied individually. The frequency of grazing and the rooting up of pasture and bracken (Pteridium esculentum) varied seasonally.
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.
Marked sites established around Port Ross in 1973 were re-examined in 1983 to measure changes in the vegetation and assess the impact of goats and pigs. Goats had not increased in numbers, nor extended beyond their earlier range, but they were seen higher on the Hooker Hills. Pigs were scarce, but their sign was seen throughout. Photopoints and numerical methods both showed that Chionochloa antarctica tussock was eliminated or greatly reduced where goats and pigs occurred together, and where only pigs were present it was reduced slightly.