Research suggests cats are one of the top threats to US wildlife, killing billions of animals each year.
Scientists from the Smithsonian Institute estimate cats are responsible for the deaths of between 1.4 and 3.7 billion birds and 6.9-20.7 billion mammals annually, the BBC reports.
They said stray and feral cats were the worst offenders but added pet cats also played a role and that owners should do more to reduce their impact.
In New Zealand, economist Gareth Morgan is campaigning to reduce cat numbers to try to preserve native birdlife.
Mr Morgan called for cats to be desexed, registered, micro-chipped and kept inside.
The authors of the US study concluded that more animals are dying at the claws of cats than in road accidents, collisions with buildings or poisonings.
The research was published in scientific journal Nature Communications.