by Whit Gibbons

August 26, 2007

Should a "housecat" stay inside? Or does a housecat get to choose when it stays inside or goes out? Cats would agree with the latter definition, but human opinions about whether cats should be allowed to roam free can be fervent and fierce.

At Cape May, NJ, outdoor cats are viewed by some people as a major threat to a rare species of bird, the piping plover, which was given protection under the Endangered Species Act in 1985. The migrating birds spend spring and summer on beaches and can become victims of prowling cats. One end of the emotional spectrum of the cat-eats-piping-plover phenomenon comes from outraged bird watchers who come to Cape May to see birds, not cats. Some ornithologists want the U.S. Fish and Wildlife Service to eliminate the unwanted predators. Meanwhile, one cat sympathizer stated that the cats should be allowed to roam free because people should let "nature take its course." The obvious response to that sentiment is that cats are not part of the natural scene on a New Jersey beach. However, other environmentalists take the position that beach housing and development have eliminated far more piping plovers and other wildlife than cats ever will. Hence the question, "if federal agencies remove the cats, shouldn't they take the same approach with developers?"

A problem some wildlife enthusiasts have with outdoor cats is that they take more than their share of native wildlife. Some biologists consider cats to be the most dangerous carnivore in many regions because of an inclination to kill, whether hungry or not, making cats a potential menace to all wildlife. Domestic cats are known as "subsidized predators," meaning they do not have to hunt to survive but have leisure time to kill for sport only.

Finding polarized positions about cats and wildlife is not difficult, Cats reportedly kill twenty million birds in Britain and three million in a single U.S. state, Virginia, each year. Yet cat defenses abound. Some ecologists maintain that proof is lacking that cat predation leads to declines in the prey populations. You may not like it when a cat snares your favorite cardinal in the front yard, but does the population of cardinals in the neighborhood decline in any measurable way? As someone once wrote to me, "I am puzzled by the concern some people have for native wildlife that suffers because house cats go outside. What exactly is the problem? No animal has ever gone extinct because of cats." I'm not sure that statement is correct, but one valid point is that birds in a yard with feeders are "subsidized prey," offsetting the subsidized predator advantage in that situation. Other justifications given for outdoor cats are that their impact on native wildlife is trivial compared to highway deaths, and "the presence of outdoor cats sharpens the senses of birds and other wildlife."

To protect native wildlife from free-roaming cats, people have sought a variety of solutions. Collars with bells reduce the capture of prey by 34-48 percent. Battery powered electronic devices that warn the prey when lights go on or alarms go off when the cat pounces toward the prey can also reduce cat predation. And a recent test in Australia of the "pounce protector, a lightweight neoprene bib worn on a collar" showed that bird captures were reduced by 80 percent. However, rest assured that some people on both sides will not view these as solutions. Some bird enthusiasts will not be satisfied if anything above 0 percent of the birds is killed. Some cat lovers would find the indignity of placing a bell, alarm system, or bib on their cat to be insurmountable.

Finally, do outdoor housecats that kill small animals have any greater environmental impact than native predators would have had historically? Do housecats simply fill a role that we have already eliminated by our removal of natural predators? As someone said, "maybe housecats are actually returning the outdoors closer to a natural system than what we have now without native predators."

Two-sided arguments about cats are likely to go on for a long time, and I'm sure I can find someone who would disagree with any position you care to take.

If you have an environmental question or comment, email

(Back to Ecoviews)