Pigs are being bred and illegally released onto conservation land across Northland, as the region struggles with a boom in numbers.
Conservationists are pleading for hunters to stop the practice, which they fear could spread one of the country's biggest biosecurity threats.
Footage released to Newshub shows rush hour in a section of original native forest in Northland, with 40 pigs filmed in just one minute.
A man who manages an area of precious conservation land, and wants to remain anonymous, says he's been complaining for years about hunters breeding pigs and illegally releasing them - and has faced threats for doing so.
"[They told me] that I was taking food off their table and interfering in something that didn't concern me and I should just stick out of it or watch myself, not go anywhere after dark kind of stuff."
He says on one side of the forest, there's a man who regularly breeds pigs and releases them into the forest, and another on the other side.
The Northland Regional Council says a minority of hunters are involved, but they're responsible for serious damage.
"There are a few out there that are doing it, and we have had situations where large numbers of pigs have been bred up and released," Northland Regional Council biosecurity manager Kane McElrea says.
Pigs have been appearing on conservation land where they were none. Images obtained by Newshub show bones and other scraps dumped in a forest, and within a day pigs have eaten it.
Mr McElrea says at the back of Waipu area, "there was pigs being fed up and bred for hunting purposes and then released - and I think the numbers sort of totalled more than 30."
Northland is already struggling with a boom in pig numbers.
They damage traps, root up the ground, eat vulnerable species such as kauri snails, and can wreck the nests of flightless birds.
The problem could also play a role in the spread of kauri dieback disease.
"There's clearly been some pig release going on," Keith Briden from Department Of Conservation (DoC) said.
"And in Northland it's particularly important to keep pigs under control because we have the kauri dieback disease and we don't want high numbers of pigs spreading the disease."
The Northland Pighunting Club condemns any release of pigs. Its secretary Victor Shortland says "people that do do it would be probably keeping it quiet because the rest of us would probably go and catch them".
Mr Shortland says it's a hunter's responsibility to manage pig numbers and stay within the law.
Newshub.
