'Ecological disaster': Cats kill 270 million animals per year, say U.K. scientists

Britain’s estimated 9.5 million pet cats are causing unknowable damage to ecosystems near cities and suburbs with how many small animals they kill near outside their owners homes, according to a new study.

Suburban cats living near natural areas kill an average of 34 animals each per year, according to researchers from the University of Reading and Royal Holloway, University of London. Cats living in suburbs surrounded by homes killed an average of 15 each per year.

Cats are best understood as a pampered non-native species, said Dr. Rebecca Thomas, one of the researchers.

“They reach incredibly and unnaturally high densities, especially in suburban environments,” she said.

“They get fed by their owners and given veterinary care so you could consider them mini super predators.”

Most of their victims are birds but those living near natural areas tended to kill more small mammals, like field mice. The study also found that feeding cats and home and making them wear bells were not a deterrent to hunting.

Researchers also noted the less visible impacts of house cats, like how just the presence of a new predator can stress ecosystems.

“Just the presence of a predator can cause wildlife to change their behaviour, either reducing feeding through heightened vigilance or staying away from a nest leaving it exposed, for example,” said Dr. Tar Pirie, the lead author of the study.

“This can reduce the survival of both adults and offspring.”

House cats also carry diseases and parasites, like Toxoplasma gondii, which can be transmitted to local wildlife.

The U.K. estimate on animals killed by cats is lower than the Wildlife Society and the American Bird Conservancy’s, who estimate outdoor pet cats kill around two animals per week. American researchers say that outdoor cats in America may kill up to 4 billion birds and 20 billion mammals per year.

Pet cats were a political issue in 2019 when U.K. farmers’ licenses to shoot birds were revoked. Tony Duckett, conservation officer for Royal Parks in London, agreed with farmers who argued that owning a cat should require a license because of how many birds they kill.