University of Georgia are recording the activities of cats using a collar camera in the aid of wildlife conservation

CATS may own the internet, but now they've been exposed as the instigators of a backyard holocaust far worse than ever suspected.

A new study published by Nature Communications shows the adorable family pets - renown for their cute and cuddly antics - kill about 2.4 billion birds and 12.3 billion mammals each year in the United States alone.

Researchers from the Smithsonian Conservation Biology Institute say both domestic and feral cats are to blame for the massacre which is some three times worse than previously suspected.

However, feral cats are believed to be the worst offenders.

The report says the cat-kill toll is higher than the combined figure from pesticides, poisons, vehicle collisions, window strikes and windmills.

Peter Marra of the Smithsonian Conservation Biology Institute said "We were absolutely stunned by the results".

The researchers methodically sifted data gathered from a variety of studies into a new mathematical model.

"Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals," the study reports.

"The big message is responsible pet ownership", Marra says, as domestic cats still catch some 1.9 billion wild animals in the US each year.

"Management decisions, both in the US and globally, must be informed by fine scale research that allows analysis of population responses to cats and assessment of the success of particular actions."