Research says cats kill tens of billions of animals a year, killing 33 species.

The number of wildlife deaths caused by cats is up to 10 billion.

Cats are one of the biggest threats to wildlife in the United States, killing tens of billions of animals each year, according to a study.

The researchers estimate that cats kill between 1.4 billion and 3.7 billion birds and between 6.9 billion and 20.7 billion mammals each year. Stray and wild cats are the culprits, the scientists wrote in the journal Nature communications. However, they also said that pet cats are also involved in the killing of wild animals, and their owners should take more effective measures to reduce the threat to wild animals.

The results show that in the United States, the number of animals killed under cat’s paws exceeds the number of animals killed by traffic crush, collision with buildings and poisoning. On islands around the world, there has been a complete record of the killing instinct of domestic cats: these felines and human beings continue to prey on local wild animals, which has caused the extinction of 33 species worldwide. However, in the mainland, it is difficult to track and investigate the predation of wild animals.

To find out more, researchers from the Smithsonian Conservation Biology Institute (SCBI) and the U.S. Fish and Wildlife Protection Agency reviewed previous studies that looked at the superb skills that cats exhibit when they hunt.

The researchers’ analysis shows that the number of cats killed is much more than that mentioned in previous studies; they found that the number of birds killed by cats is more than four times of the previous estimates. Native American birds, such as the robins, are at greatest risk, while rats, shrews, wild mice, squirrels and rabbits are the most likely mammals to be killed.

“Our research shows that cats pose the greatest threat to wildlife in the United States,” said Dr. Peter Mara of the Smithsonian Institute of conservation biology.

“Ownerless cats” are divided into stray cats, wild cats and farm cats, which kill about three times as many wild animals as pet cats, the team said. However, the researchers said that pet cats are still killing a large number of animals, and their owners should take more measures to limit the killing of pet cats.

Dr. Mara said: “in this study, the number of deaths in wild animals is very high. We hope that some pet cat owners will trust our research results and keep their cats indoors; we also hope that the research will attract the attention of policy makers, wildlife managers and scientists – the number of wildlife deaths caused by cat predatory behavior is huge. ”

A spokesman for RSPCA, an animal charity, said: ‘using the right collar and bell will reduce the success rate of cat hunting by at least a third.