For Rodent Control, Cats Are Over-Rated

Do you ever get tired of hearing people say, “We don’t have mice because we have a cat”? I do. In urban areas, when a house cat kills the occasional rodent, their owners beam proudly, “Thank you Tabby...Such a good cat!” And this notion also seems especially persistent among farmers and rural folks. In a study I conducted, 52% of Indiana poultry farmers kept cats (as many as 10) on their farms solely for the purpose of controlling mice.

This confidence people have had in cats as rodent controllers is worldwide and began with the start of civilization. The ancient Egyptians employed cats in their granaries in efforts to control the thieving mice, and honored the cat-goddess Bast, in appreciation of the cat as a pest controller. Each of us has seen pictures, cartoons and children’s stories depicting cats as the ultimate (and “natural”) mouse killer. And to this day we are constantly reinforcing the image with various things we say.

So is it myth or fact? What is the impact of cats in controlling rodents around our buildings, and upon our urban environments in general? Let’s take a closer look at the cat and its behavior, as well as the various types of cats found in urban and suburban environments.

THE HOUSE CAT. Felis domesticus is a member of the mammalian order Carnivora, which generally comprises opportunistic predators (e.g. foxes, raccoons, dogs, coyotes, bobcats, mountain lions, etc.). In urban areas, including cities, suburbs and rural areas, the house cat may be an indoor pet, a feral (wild) cat, or a semi-feral cat.

As a house pet in the United States, the cat has replaced the dog as the No.1 pet, and estimates now place the number of pet house cats at approximately 58 to 60 million. These cats are usually well-fed, de-clawed, cared for by people and never allowed outdoors. The psychological value of these cats to their owners is often quite significant — they truly serve as companions. The behavior of these cats and their impact on the local urban environment varies depending on their food supply as provided by people and nature.

Feral house cats are cats that were, at some point, abandoned and have reverted back to a “wild” state. Feral cats fend for themselves and feed on whatever opportunity presents. In inner city areas, this includes garbage, insects, birds, the occasional rodent and whatever else they can find.

People sympathetic to the plight of abandoned cats place out cat food on a daily basis, which has resulted in population explosions of feral and semi-feral cats. In rural areas and areas away from buildings, feral cats that do not have access to human food are predaceous on insects, small mammals, birds, fish, snakes and carrion.

The impact of these cats on local wildlife can be devastating. In fact, the house cat is the top predator of the urban and suburban ecosystem. One study conducted of England’s 5 million house cats estimated the cats claimed an annual toll of approximately 70 million animals and birds. The toll on desirable song birds can be particularly devastating. In my own yard, I have watched my neighbor’s “house cat” stalk my birdfeeder daily. This cat was highly effective in capturing many young song birds.

So house cats roaming suburban yards are not exactly helping to enhance the wildlife of an area. They not only decimate some of the desirable song bird population, they kill other desirable mammals and the natural predators of rodents (e.g. snakes).

PLAYING CAT AND MOUSE. But what about the cat’s role in helping to control mice and rats? It is well-known the house cat commonly preys on the house mouse — when the opportunity presents itself, and if the cat is interested. In many cases, however, the mouse is quite adept at escaping from a cat. Consider for example, that a healthy mouse can move at 12 feet per second in its effort to avoid predators. But with the older, sickly, or near-death mice, Tabby is going to look pretty good when bringing these mice to the nondiscriminating homeowner.

But killing the occasional mouse, and controlling an infestation are two different activities. In general, cats are not responsible for keeping buildings rodent-free or keeping rodent populations in check. The most generous we can be toward the cat and its role in mouse control is to admit that by random luck, a cat may occasionally be successful in capturing and killing the mouse that has just entered the house. Should the mouse be a pregnant female, then the cat has in fact, stemmed off a possible infestation.

On the other hand, sometimes cats actually bring in mice that normally would have stayed outside. Most of us have been in this situation, saying “look what the cat dragged in,” as the cat brings in a near-death, in-shock mouse for a toy, or for delivery to its owner’s feet. The most serious consequence of such “gift giving” could be what happened in a recent situation, in which a cat dropped a deer mouse on the lap of its proud owner. “Why thank you, Tabby. Such a good cat.”

Unfortunately this woman contracted the deadly Pulmonary Hantavirus several days later.

Many homes, both with and without cats, never experience mouse infestations, and there are many reasons for this: the specific environment, tightness of the home, random luck, etc. The difference is that within homes with cats, the homeowners credit their cats in keeping the home mouse-free.

Some people believe that the odor of cats in and around a home serves as a natural deterrent to rodents outside the home. However, there is no research to support this. It may be true in certain cases, but effects of cat odor as a mouse deterrence would be unpredictable at best, and would likely vary significantly depending on many things.

CATS AND RATS. And what about cats and rats? Studies as early as 1910 observed that cats are not effective in controlling rats. The well-known rodentologist Bill Jackson found in 1951 that Baltimore cats did nothing more than catch rats that would eventually die from one cause or another anyway. Their predation had not reduced the rodent population. More recently in 1986, Dr. J. Childs conducted research on city cats and rats that found a size-dependent selection of rats by cats, whereby cats will catch only juvenile or sub-adult rats, and do not complete their chases of adult rats. He observed, “although adult cats and larger rats were frequently observed in close proximity, no aggressive behavior was directed by rats toward cats, and generally these species co-exist peacefully in alleys.”

So despite popular press and the lay public’s perceptions, cats are not important contributors in rodent control for the typical urban environment. Perhaps the myth of cats as great mousers is so well established because people have a tendency to lavish undeserved credit and attention on those they love. How else could you explain housing, feeding and caring for an animal which doesn’t respond to commands, lays around the house all day, and doesn’t provide any work in return? Perhaps maximizing and exaggerating the cat’s role in keeping our domiciles free of rodents as their “work” is the best we can come up with in justifying this highly one-sided relationship.

No offense to cat lovers, but for a mouse problem, get a truly effective rodent predator — a pest management professional.

Dr. Robert Corrigan, a contributing editor to PCT magazine, is president of RMC Pest Management Consulting. He can be reached at RMC Pest Management Consulting, 5114 Turner Road, Richmond IN 47374, 317/939-2829.