Domestic cats may be cute and cuddly, but they're also adept hunters. In the United States, cats kill billions of birds and small mammals a year, experts say.
But where does all this carnage happen?
Near people's houses, a new study suggests. And not because cats don't wander far from home. Instead, it's that cats avoid natural areas where coyotes live, said Roland Kays, a zoologist at the North Carolina Museum of Natural Sciences and the lead author of a study published last month in the Journal of Mammalogy.
Over two years, Kays and his team recruited 486 "citizen scientists" to help track the whereabouts of domestic cats across six states in the eastern United States. Kays loaned each of these volunteers a motion-sensing camera to mount in a tree for three weeks. The cameras were set up to automatically snap a picture whenever they detected an animal moving nearby.
The citizen scientists deployed the cameras in backyards and urban woodlots in Raleigh, N.C., or in one of 32 protected natural areas in North and South Carolina, Tennessee, Virginia, and the Washington, D.C., area.
"Working with the volunteers was key to being able to scale [the research] up and survey over such a big area," Kays said.
After three weeks, the citizen scientists retrieved the memory cards from their cameras and attempted to identify the animals that were pictured. Then they moved the cameras to new sites.
They also gave the memory cards to Kay's team of professional scientists who verified the identities of all the animals.
By the end of the study, the cameras had taken more than 50,000 pictures of coyotes, deer and other wildlife, in 1,953 locations in protected areas. Those same cameras in the protected areas only took 55 photographs of domestic cats in the same time period.
Cameras at 171 sites throughout the urban Raleigh area photographed both cats and coyotes. Cats were most commonly spotted in residential yards -- places where coyotes were rarely seen. To wit: Cameras in residential yards were 300 times more likely to spot a cat than cameras in protected areas, researchers found.
By overlaying the photographic data with maps of housing density and coyote abundance, researchers were able to figure out that coyote activity was the most important factor in determining where cats were seen.
Notably, the only protected area where researchers didn't photograph any coyotes (Gambrill State Park in Maryland) was also the one where the most cats were spotted. This reinforces the notion that coyotes keep cats out of the wild places, researchers wrote.
"Coyotes will kill cats," Kays said. "That's one of the benefits of having predators in the environment -- they help keep the balance of nature and help prevent cats from overrunning it."
So the billions of birds and small mammals that fall victim to domestic cats each year probably live in or near urban areas, Kays said.
"California has a number of endangered small mammals that live close to development," Kays said. "That's where cats could be a real problem."