Turning into my driveway last night, I caught a glint of yellow eyes and a flash of white fur. Hitting the brakes just in time, I realized that my neighbor’s cat was out again- and on the hunt. She crouched at the side of the driveway, back hunched protectively, paws on the ground in front of her. As I got out of the car and approached, distracting the cat, a small, dark creature wriggled free from her grip and hobbled towards the safety of the lawn. “Oh no,” I groaned. Our local domesticated predator had struck again.
Many people wonder what they can do for conservation and how they can make a real difference both in their community and globally. One fairly substantial answer: keep your cats indoors. While cats may look sweet and harmless, they are natural predators, and the ancestors of domestic cats (and feral cats today) hunted rodents, birds, reptiles, and other small wildlife to survive. Pouncing is an instinct for cats, and when young cats “play with their food” they may be honing their hunting skills- learning to time their strikes based on the movement and distance of the prey item, coordinating their movements to successfully capture their target.
Most cat owners whose cats roam free have come home to find limp and lifeless “gifts” on their doorstep, or have observed their cat sneaking up a tree in which a bird’s nest hides in the crook of a branch. But we usually only observe our cats killing a few birds or mice- how much of an impact can this really have on wildlife populations?
The answer is- plenty. One 2011 study by Anne Balogh, Thomas Ryder, and Pete Marra showed that in Washington, D.C., predation accounted for 79% of all Gray Catbird deaths, and almost half of the observed predation was attributable to domestic cats. A 2003 study by Michael Woods, Robbie McDonald, and Stephen Harris in Great Britain estimated that over a period of 5 months, domesticated British cats brought home between 85-100 million prey items, including mammals, birds, reptiles, and amphibians. In southeastern Michigan, a 2003 study calculated that during the breeding season, free-ranging cats killed a minimum of one bird per kilometer per day, for a total of ~16,000-~47,000 birds killed over the course of the breeding season in this area.
However, the number of wildlife kills by cats is hard to study, and much past research has relied on reports from cat owners. A new, innovative study attached “Kitty Cams” to 60 cats in Georgia to record the cats’ behavior, day and night. The results were alarming. Although much of the scientific literature focuses on the impacts of outdoor cats on bird populations, the Kitty Cams showed that among these cats, 41% of prey items are reptiles, with mammals comprising 25% and birds 12%. These clever cameras also suggest that owner reports of cat kills are drastically underrepresenting the impact of predation; only about a quarter of prey was brought home by these cats, with almost half left to rot.
Many of us are familiar with the devastating effects that invasive species can have on single species and entire ecosystems; in fact, NatureServe identifies invasive species as the second biggest threat to endangered species, second only to habitat loss. European gypsy moths caused hundreds of millions of dollars of destruction in eastern U.S. forests, feral hogs have devastated local plant communities in the Great Smoky Mountains National Park, and the chestnut blight fungus of the late 19th century wiped out almost every single chestnut tree in the eastern U.S. Domestic cats, too, are an invasive species, and most wildlife communities are not adapted to avoid these skilled predators.
So, if you’d like to play a more active role in conservation in your community, consider keeping your cats indoors. Your cats will live longer, and your local wildlife community will thank you.
For more information about the Kitty Cam research, and to watch Kitty Cam videos, see:
For additional information on domestic cats’ impact on wildlife, go to:
For an opinion piece on how keeping cats outdoors is bad for both wildlife and the cats themselves, check out: