(CNN) When your house cat trots outside for a neighborhood stroll, it doesn't end well for birds, bunnies, squirrels and other wildlife. And now, thanks to a new study, we know how much damage our feline friends can do.

In fact, they kill even more prey than wild predators similar in size to cats, and they don't have to go far to do it. The average range for pet cats allowed outside is about 328 feet from the house they live in.

"We found that house cats have a two- to 10-times larger impact on wildlife than wild predators -- a striking effect," said Roland Kays, lead study author and zoologist at the North Carolina Museum of Natural Sciences.

To track the behavior of house cats who were allowed to go outside, 925 cats across six countries were fitted with unobtrusive GPS devices. Scientists and citizen scientists used the data to track how far the cats ranged, as well as any prey they captured and brought home across rural and urban areas in the US, the UK, Australia and New Zealand.

The study published Wednesday in the journal Animal Conservation.

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