Cats Face Threats—and Can Cause Them—When They Roam

Letting your cat roam outdoors can be dangerous for your pet as well as the ecosystem.

Although some pet owners think cats need to explore, a new study suggests that there are many potential risks for their outside adventures. The cats could be exposed to disease and they could prey on native wildlife.

“It is well known that both cats and wildlife are at risk when cats are allowed outdoors. However, the extent to which those risks are realized is less well known, which can limit our ability to manage the situation in the best interest of all species involved,” lead author Daniel Herrera, a Ph.D. student in the University of Maryland’s Department of Environmental Science and Technology, tells Treehugger.

“Our research was driven by a desire to inform more effective and humane population management practices for outdoor cats to protect cats and wildlife alike.”

For their work, researchers analyzed data from the D.C. Cat Count, a survey in Washington, D.C., that used 60 motion-activated cameras in 1,500 locations. The cameras recorded which species cats preyed on, as well as where they overlapped with wildlife that could transmit disease to them.

They found that the average cat in the area has a 61% probability of being in the same space as raccoons, which are the most common rabies-transmitting animal in the U.S. They also have a 61% overlap with red foxes and a 56% overlap with Virginia opossums, both of which also can spread rabies.

This exposure can threaten their own health, as well as the safety of their humans once they return home, researchers say.

Free-roaming cats were also found to prey on native species including chipmunks, gray squirrels, cottontail rabbits, groundhogs, and white-footed mice. When they hunt those species they can harm the ecosystem by reducing biodiversity.

The results were published in the journal Frontiers in Ecology and Evolution.

Outdoor Threats

Researchers noted some unexpected animals when combing through the camera footage.

“Our most shocking observation was of a bobcat in northwest D.C., which was the first bobcat ever to be recorded within the municipal boundaries of the city (excluding those at the zoo, of course)! Other notable species included beaver, otter, and muskrat,” Herrera says.

“When people think of Washington, D.C., they might think of the White House or the Capitol Building. But what many don't realize is that DC has the highest proportion of park land of any American city (about 6,700 acres, amounting to about 20% of the city's land). As a result, D.C. residents share the city with a multitude of wild neighbors ranging from flying squirrels to bobcat, and even the occasional black bear (although we did not observe any black bears in this study)!”

When cats are permitted to go outside, they face threats from vehicle collisions, being hunted by other predators, and maybe even ingesting poison put out for rats or other animals.

Researchers point out that many people think their cats are out stalking non-native animals like rats, when they are actually more likely to hunt small, native species.

“When cats roam, they also present direct and indirect dangers to wildlife. Cats are prolific hunters and are known to kill an astronomical number of native animals each year, which is often not necessary for the cat's survival since it is fed by humans,” Herrera says.

“Even if a cat doesn't hunt, however, it can still have negative impacts on wildlife. For instance, the mere presence of a cat applies enough pressure to some bird species that mothers will abandon their nest, or will spend so much time being vigilant of the potential hunter that she neglects to feed her chicks. The simple solution is to keep cats indoors and avoid these risks altogether.”

Researchers noted that there’s a connection between the presence of wildlife and whether there is tree cover and water. However, the presence of cats decreased with those natural elements and instead increased with higher human population density.

These associations clash with the belief that free-roaming cats are filling a natural role in the ecosystem when they hunt wildlife.

“An interesting result from our study is that cats are positively associated with human development while wildlife tend to be negatively associated with dense human development. This finding implies that cats are dependent on humans for their survival, whereas wildlife are not,” Herrera says.

“Since cats have such a strong association with humans we can conclude that cats need humans to live at high densities, as they do in urban areas. If cats are dependent on humans, then any hunting they do is not 'natural' since humans have facilitated it.”

And there’s the added threat of zoonotic disease, when cats are permitted to roam, are potentially exposed to situations where they might contract rabies, and then are allowed back into the home.

“Animals in urban environments are already coping with unique challenges such as habitat loss and reduced habitat connectivity. The additional pressures applied by cats only adds further stress to an already strained ecological system,” Herrera says.

“Similarly, the natural world is already struggling to cope with rapid climate change, human population growth, and rampant biodiversity loss. While some ecological strains might be out of our control, every cat owner has the opportunity to contribute to a healthier Earth by keeping their cats indoors.”