The answer is both.
Domestic house cats are highly skilled predators and outdoor cats living near or adjacent to natural areas are likely to prey on many of our nature neighbors. A domestic cat’s motivation to hunt is strong and even your well-fed cat will prey on local birds, small mammals, and reptiles if given the opportunity. Unsuspecting birds that benefit our gardens and natural areas by pollinating plants, spreading seeds, and controlling insects are often at risk of becoming prey of the predator driven instinct of our outdoor cats.
Cats that roam around outside are at risk of: becoming prey of wild predators, being attacked by domestic dogs, getting into fights with other cats, or getting hit by a car.
Domestic cats as predators
Although many of our cats are affectionate pets, they can hunt as effectively as wild predators. Free ranging cats that roam outdoors are a threat to our local wildlife. With more than 70 million pet cats and over 60 million stray cats in the United States, scientists estimate that cats are responsible for killing billions of wild animals, such as birds, reptiles, and small mammals (e.g. rabbits, mice, voles, squirrels) in just one year. Researchers studying the effects of cats in parks found that there were 50% less birds in a park with 25 cats compared to a park with no cats. They also found that two common types of ground-dwelling birds — California Quail and California Thrasher — could not be found in the park with cats.
Outside cats are not only predators but they are also competitors. Local wild predators such as foxes, skunks, raccoons, opossums, weasels, coyotes, bobcats, hawks, and owls rely on the native populations of prey animals to survive. Our well-fed house cats do not need to kill native prey animals to survive, but they often kill them from an instinct to hunt that is independent of the urge to eat. Overall, cats can reduce the availability of prey available for our native wildlife.
Keep your cat safe.
It is a dangerous world outside for your beloved pet. If your cat is roaming around the neighborhood he is at risk of being injured or killed by wild predators, domestic dogs, hit by a car, fighting with other cats, ingesting poisoning (from eating poisoned rodents), or contracting diseases. Keeping your cat indoors is the best way to keep them safe.
How you can help
LinksAmerican Humane Association
American Bird Conservancy
Wild Things Sanctuary
The Impact of Free-Ranging Domestic Cats on Wildlife of the United States