From the April 2012 Conservationist
Photo: Paul Clark
The Ultimate Hunter
Domestic cats and wildlife populations
By Christine Donovan
She cringed. She didn't even have to look down to know that her foot had just grazed the top of another dead bird. It was seven o'clock in the morning and she had stepped outside to get the newspaper, but instead was greeted by another "present" from her cat Trixie.
While not every cat owner has stepped on a wild animal first thing in the morning, most outdoor cat owners are familiar with the "gifts" (both live and dead) brought to them by their cats. What many people don't realize, however, is that these gifts are representative of the harm their cats can cause by going outdoors.
Americans are just learning about the dangers posed by domestic cats that spend some or all of their time outdoors. And while it may be hard for us to imagine that those adorable, purring members of our families can be a threat, the reality is that domestic cats are incredible hunters that take a huge toll on wildlife populations. In fact, through injuring and killing prey, house cats represent a serious ecological threat, and in many suburban and rural areas they are the most abundant predators.
These are the cat-killed birds brought
into the Portland Audubon Society
in one season. (Photo: Portland
According to The New York Times, domestic cats kill more than one billion (yes, I did say billion) small mammals and about one billion birds each year nationwide. That's more than 100,000 times the number of birds killed by the BP oil spill.
A common misconception is that a cat fed at home will not kill animals. However, it appears that domestic cats' instincts to hunt are separate from their hunger senses. Owners of outdoor cats know this firsthand: they feed their cats well, yet cats still bring home "gifts." A study from 1976 featured in an article by American Bird Conservancy highlighted six cats eating a food that they enjoyed. However, when a live mouse was put in the room, each cat stopped eating to kill the mouse, and then continued eating its food. In one study, a well-fed cat killed more than 1,600 animals in 18 months. Even if the cat lets the prey escape alive, the prey almost always dies from stress and/or infections from the cat's teeth or claws.
Cats have the greatest impact on bird populations. According to Wildlife Professional magazine, domestic cats have had documented impacts on 254 species of threatened, near threatened, and extinct bird species worldwide. In the U.S., almost one-third of bird species are endangered, threatened, or in significant decline due to stresses such as habitat destruction. Meanwhile, the number of house cats has almost tripled in the last 50 years.
American Bird Conservancy states that house cats' main prey includes rabbits, squirrels, chipmunks, cardinals, blue jays and house wrens, and they will also prey on the endangered piping plover, Florida scrub-jay and the California least tern. A cat roaming outdoors averages 14 kills per year, and there are more than 100 million outdoor and feral cats in the U.S. The numbers add up, and directly affect the food available for native predators.
Cats are a particular threat in the early summer, during birds' vulnerable fledgling stage. Many people think that attaching a bell to their outdoor cat will keep it from catching prey, but this is not the case. Studies show that the bell usually does not alert prey until it is too late, or not at all.
Pet owners can help by keeping their feline companions inside. This protects wild critters, and is also good for the cat's own safety. It has been well-documented that cats that roam freely outdoors live between three and five years, while cats kept exclusively indoors live between 10 and 17 years. Outdoor cats are hit by cars, fall prey to wild predators (fox, fishers, mink, coyote, owls, hawks), and can be exposed to poisons and diseases. In fact, thousands of cats are killed each year due to poisons such as pesticides, rodenticides and antifreeze, while others contract deadly diseases such as rabies, feline leukemia, distemper and feline immunodeficiency virus. Keeping cats indoors can benefit their owners, as well. Outdoor cats can bring fleas, ticks, diseases and parasites into the home, exposing their owners to these hazards.
Parasites occur in much higher numbers in outdoor cats than in their exclusively indoor counterparts. One study found hookworm in 75% of feral cats. Furthermore, many diseases that domestic felines can carry are highly contagious and can go undetected by the cat's owner. The illnesses that your cat carries may not only be harmful to it, but also to wildlife. For example, in the western U.S., house cats have spread feline leukemia to mountain lions, and in Florida, domestic cats may have infected the endangered Florida panther with feline distemper and an immune deficiency disease.
When you consider that domestic cats born and raised entirely outdoors have an almost 80 percent annual mortality rate, and that in a given year millions of outdoor cats do not come home, indoor life for a cat looks attractive. Owners of outdoor cats are nervous that their cats will be miserable indoors, but in fact, cats raised exclusively indoors generally show no desire to go outdoors. So if you want Trixie to stop leaving you inconvenient gifts, consider easing her or your next cat into life indoors. You'll be extending her life, and protecting local wildlife at the same time.
A senior at SUNY Geneseo, Christine Donovan was a summer intern at DEC.