They’re highly skilled hunters, they kill even when they're not hungry and our native bush is a gourmet feast for them.
Cats are our favourite pet - 40 percent of households have at least one, and all up there are 1.2 million domestic cats out there.
Feral cats are estimated to number in the millions.
But our love of cats has made them a no-go area in conversations about pest eradication projects.
It’s so contentious that cats have been left off the Predator Free 2050 list of pests.
Today, The Detail looks at the growing calls for more resources to get rid of feral cats, and to bring in tighter regulations on pet felines.
"We have to have a conversation about it if we're going to ensure our unique, endangered wildlife doesn't become extinct. And it’s not about being anti-cat," says Tamsin Orr-Walker, chair of Kea Conservation Trust.
She's seen the impact of feral cats on kea: a once-thriving population of the birds at Nelson Lakes was slashed by nearly 80 percent over 10 years.
Footage from cameras shows "constant invasion of these nests by rats, possums and stoats, and then of course we started over the years seeing invasion of feral cats," Orr-Walker says.
A network of live-capture cat and possum traps was set up - live because kea can also get caught in the traps. When an animal is caught it triggers a signal to the Department of Conservation at St Arnaud.
"Someone has to get to that trap very, very quickly to make sure that whatever is in there is dealt with, either released if it’s a kea, and euthanised humanely if it is a cat or a possum,” she says.
Orr-Walker, like other conservationists, is frustrated by the growing number of well-meaning but unregulated community groups running the ‘trap-neuter-return' programmes for feral cats and dumped pets.
"They are so feral that they cannot be tamed, you'll get feline AIDS in that population, cats are the one carrier of toxoplasmosis. Some have been caught and rehomed, which is great, but to actually then support re-releasing those animals back out that can't be rehomed is absolutely criminal," she says.
Predator Free New Zealand Trust chief executive Jessi Morgan says they are one of New Zealand's worst ecological problems because of the "impact a single cat can have".
"Our native species aren't equipped to deal with them," she says.
"Our native species have quite a strong scent and their reflex when they are threatened is to freeze, so for a mammalian predator both those things are really helpful if you are going to be hunting one of our native species."
A number of conservationists and trappers spoken to by The Detail refused to go on the record about feral cats, because of the backlash from cat lovers.
But New Zealanders’ views are changing, as community groups involved in pest control, trapping possums, stoats, ferrets and rats start to recognise that feral and dumped cats are undermining a lot of work that they are doing, says Morgan.
Judy Gilbert has been battling the pest problem on Aotea Great Barrier Island for decades at the Windy Hill Sanctuary.
She’s also involved in the ambitious new Tū Mai Taonga project to get rid of feral cats and rats and re-introduce lost species.
"This is a bottomless pit, suppressing these animals. We urgently need to eradicate the cats and rats off this island for it to make a significant difference as a biodiversity arc."
Gilbert says there has to be an agreement with the community about allowing domestic cats that are spayed and neutered.
"You'd have a little bit of carnage, but I think that that could be tolerable from a smallish number of companion cats. It’s a concession."
