A Doc team recently found fresh signs of pigs, and a farmer has seen some on his boundary with the national park.
Doc South Westland operations manager Wayne Costello said about 25 pigs were thought to have been illegally released in the Saltwater Forest area of the northern section of the park in July 2021.
It was irresponsible and jeopardised all the work that has gone into rowi (Okarito kiwi) conservation, Mr Costello said.
"Pigs wreak havoc for ground nesting birds, such as kiwi and their young, as they will corner, kill and eat kiwi and wreck their habitat through trampling and rooting. Now they're just a small swim across a river into neighbouring rowi habitat."
As well as the danger they pose to birds, pigs eat seedlings and young trees, ringbark mature trees, damage tracks and cause erosion.
Pigs are also a known vector for bovine Tb so there is a risk for local farmers if these pigs were brought in from outside South Westland.
It is illegal to release pigs anywhere. Pig populations expand quickly as they have multiple offspring and no natural predators.
"It seems there are now significant numbers of pigs scattered widely through the northern section of the park which is an ecological catastrophe," Mr Costello said.
The statutory body with responsibilities for game animals and hunting, the Game Animal Council (GAC), has also condemned the release.
"The illegal release of any game animal is extremely disappointing and to release pigs so near to a critical kiwi habitat is particularly reckless," GAC general manager Tim Gale said.
"Pigs are an adaptable species that can become established in an area quickly. While they are a valuable food resource for many communities, that is absolutely no justification for intentionally spreading them into a national park."
