A conservation group is backing a campaign to reduce ownership of domestic cats because it says they are killing native wildlife.
Economist Gareth Morgan has launched a website which calls cats natural born killers and gives reasons why people should not own the animals.
The website 'Cats to Go' says they don't just kill rodents but also native and introduced birds, skinks and insects.
Advocacy manager for Forest and Bird Kevin Hackwell says a recent study in Dunedin showed the animals were killing native birds like fantails.
Mr Hackwell says people should be responsible with their pets and consider not replacing them when they die.
Mr Morgan's site says people should keep cats inside 24 hours a day and, if that's impractical, ensure that when the time comes it is the last cat they own.
The site says it is not necessarily suggesting owners go out and have their cat euthanised but that is an option.