Not the cute, cuddly feline friends we call pets—feral cats are stealthy predators having a severe impact on New Zealand’s native wildlife.

The Department of Conservation (DOC) is fighting an uphill battle to control these pests throughout the Canterbury region.

In Mid Canterbury, birdlife along braided rivers is under increasing threat as wild cats run rampant, says Geraldine DOC senior ranger biodiversity Ian Fraser.

“Cats are an enormous problem, and we are trying to protect braided river birds,” Fraser says.

“Feral cats are such versatile predators, and they are devastating the braided river, dryland and tussock ecosystems we have in the Ashburton basin.”

Fraser believes feral cats may be even more prevalent in the Ashburton Basin than in forested areas.

“They seem to be more dominant out here.

“We don’t have so many rats and possums as they do in the forests, but the cat population is out of this world.”

Endangered species such as the black stilt, wrybill, and black-fronted tern are particularly vulnerable to predation by feral cats in South Island braided riverbeds.

Cats were first introduced to New Zealand aboard ships from early European settlers, brought to control rats during the voyage.

Over time, they spread across the country.

Larger and more adept hunters than their domestic counterparts, feral cats are also known to spread diseases such as toxoplasmosis -dangerous to human and stock.

Stealthy by nature and capable of travelling long distances, feral cats are difficult to count and monitor.

Fraser says DOC is turning to technology for help: trail cameras driven by artificial intelligence are in development, as manually counting cats in camera footage is too labour-intensive.

“They are hard to count, they are pretty cryptic.”

Currently, most population estimates come from trap data—and the numbers are staggering.

“In the last three years in the traps in the Upper Rangitata and Stour Valley we have removed 1,346 cats.”

Although black-fronted tern survival rates appear to have improved since the trapping programme began, Fraser says the issue remains overwhelming.

“The cats just keep pouring back in.”

DOC is working closely with farmers and catchment groups to reduce the problem.

“Farmers give us access to their properties, so sometimes our traps are on farmland.

“We also do some rabbit control, because that’s often a cat’s prey base.

“They might snack on birds, but their day-to-day diet is rabbits—if they are around.

“So, keeping rabbits under control helps keep the feral cat population down,” Fraser said.

In North Canterbury, the problem is concentrated in forests where DOC is focused on restoring populations of the critically endangered orange-fronted parakeet, or kākāriki karaka—a bird native to the area.

“It would be a great shame if we lost these, but it's hard maintaining populations when you get predators invading—and of course cats are one of those,” says Rangiora DOC senior ranger biodiversity Archie Macfarlane.

Parakeets are particularly vulnerable when foraging for beech seeds on the forest floor in autumn and when fledgling chicks spend significant time on the ground.

“We have footage of cats hanging around the base of nesting trees.”

Macfarlane says native birds are especially susceptible because they haven’t evolved to recognise cats as a threat.

“They don’t necessarily understand they are a predator.

“If a falcon flies over, they will stop moving and sit down.

“But they may not have that predator recognition behaviour for cats.”

He considers cats the most dangerous predator DOC is dealing with.

“There are not many species they won’t be predating on.

“While our primary focus is protecting kakariki, we are also trying to protect a lot of other critical endangered native species.”

Trapping and euthanising remain the primary methods of control, but they have limitations.

However, a new meat-based bait developed for aerial application is showing promise and may become a game-changer in the effort to make New Zealand predator-free by 2050.

As part of the Predator Free 2050 initiative, DOC—working with pest control company Orillion—is developing a meat-based sausage bait specifically for feral cats.

Early field trials have produced encouraging results.

In a 5,000-hectare aerial trial in North Canterbury’s St James Conservation Area, one 18g sausage bait was dropped per hectare.

GPS-collared tracking showed that 9 out of 10 monitored cats consumed the bait and died.

Motion-activated cameras recorded a sharp drop in cat activity, falling from 63 detections to just one.

A second trial at Macraes Flat in Otago, which was recently completed, has shown similar results with 100 per cent (11 out of 11) of monitored cats dying.

by Claire Inkson