Feral pigs causing ‘devastating’ damage to native bush

The impact caused by a little-known pest in the Hunua Ranges is being studied in a new joint university and Auckland Council research project.

Auckland University Masters student Robert Vennell is calling for volunteers to join him on feral pig research trips into the native bush of South-East Auckland.

His thesis project, a joint venture between Auckland University and Auckland Council, is monitoring the impacts of feral pigs on the environment with motion capture cameras.

Footage similar to what will be shot in the Hunua Ranges was captured in the Waitakere Ranges in 2015. Video: Robert Vennell

“Pigs can cause a lot of damage to native environments as they are a predator of many of our native species: ground nesting birds, frogs and also a lot of invertebrates,” said Mr Vennell.

Department of Conservation scientist Kath Walker said feral pigs are "devastating predators" to anything that lives on the forest floor.

Among those native species affected are the Powelliphanta snail, a carnivorous snail that lives in native New Zealand bush.

“They [feral pigs] love eating the snails themselves, which are a big chunk of protein for the pigs, and they also eat their eggs,” Ms Walker said.

Mr Vennell’s research aims to find what is called the “damage function” so he can understand the relationship between the number of pigs the environment has and the amount of damage they cause.

“Pigs have a really good sense of smell, so they can smell food items in the ground, they’ll locate it and then dig up the ground with their snout. And if you get a lot of pigs in the area, that means they can just plough up the entire forest,” he said.

The destructive threat posed by feral pigs is not a new issue.

Jonathan Miles, spokesperson for Biosecurity at the Auckland Council, said feral pig research has been “ongoing for a long, long time”.

“Research has been done elsewhere in the country on feral pigs as well and they do have an impact on the environment.”

Mr Vennell doesn’t plan on hogging his research. His recordings will give the Auckland Council information about a control target on pest numbers so they can “reduce the pigs to a certain density".

For anyone interested in joining Robert Vennell on his expeditions into the Hunua Ranges, he can be contacted on email.