People who do not like neighbours' cats wandering on to their properties should set live capture traps and hand the marauders over to the council, economist Gareth Morgan says.
The millionaire philanthropist is campaigning to get rid of cats, which he says are killing native birds and have already contributed to wiping out nine species.
Killing the animals is not necessary, but is an option, his new Cats to Go website says.
"The choice we face is clear: cats or conservation," Dr Morgan said yesterday. "We claim to be clean and green, yet half of Kiwi homes are harbouring serial wildlife killers.
"I am advocating responsible pet ownership, not for people to bop their pets on the head. To me, a responsible pet owner has their cat neutered, keeps it well fed and indoors as much as possible, and puts a bell on them. Then when their cat dies, I think people should consider not replacing it.
"We appreciate the fact that you have an emotional connection with your pet and that pet ownership is a rewarding experience.
"But there's a real problem with cats - they kill for pleasure, and most of that killing is out of your sight so probably out of your mind."
He also calls for domestic cats to be registered, chipped and neutered, as dogs are. To stop cats wandering, he says neighbours should be encouraged to set live capture cage traps on their property and turn "the miscreants" over to the local authority.
Wellington SPCA chief executive Iain Torrance said he was surprised and disappointed by Dr Morgan's campaign.
While he agreed about responsible pet ownership, he said some of Dr Morgan's statements were "a bit radical and over the top". He questioned the validity of his research.
"It is disappointing that he has chosen to take such a hard line towards an animal that provides comfort and companionship to children, the elderly and the wider community."
When Wellington SPCA came across stray cats, it neutered them and released them, which was effective in reducing the number of strays. Eradicating cats from an area did not work if there was food available, as other cats would move in, he said.
Karen Jones, of Ngaio, who has four of her own cats and is fostering seven kittens for the SPCA, backed many suggestions, including putting bells on cats and keeping them inside when possible.
But a cat-free New Zealand was too severe, she said. "You can't put one species above another one."
If cats disappeared, numbers of pest species, such as rats, would increase.
Earlier this month Unitec researcher Mark Farnworth estimated there were 1.4 million cats nationally, with potentially another 350,000 in the wild.
But John Innes, from Landcare Research, said while endangered native birds were at risk, they did not tend to live in urban centres, meaning cats were not the major killers.
"If you look at cat diets, they live off rodents, rats, mice, small rabbits, things like that."
This led to them eating ship rats, which preyed on native birds.
- The Dominion Post