Should domestic cats be allowed to roam freely outdoors? This is a controversial issue. Those who say yes say they are standing up for outdoor cats and the people who care for them. Critics respond that free-roaming cats kill so many important birds, reptiles, mammals and insects like butterflies and dragonflies that they threaten biodiversity globally.
As conservation biologists familiar with these conflicting views, we wondered if there was room for a more nuanced strategy than the typical yes/no impasse. In a recently published study, we used camera traps at hundreds of sites across Washington, DC, to analyze the predatory behavior of free-ranging urban cats. The cameras recorded all cats that passed them, so our study did not distinguish between feral cats and pet cats roaming outdoors.
Our data showed that cats were unlikely to prey on native wildlife, such as songbirds or small mammals, when more than about 500 meters (1,500 feet) from an area. wooded, such as a park or wooded backyard. We also found that when cats were around 800 feet (250 meters) or more from forest edges, they were more likely to prey on rats than native wildlife.
Since the average urban domestic cat ranges over a small area—about 170 meters (550 feet) or one to two city blocks—the difference between a diet consisting exclusively of native species and one with no native prey can be felt in one litter of the cat. Our results suggest that focusing efforts on managing cat populations near forested areas may be a more effective conservation strategy than trying to manage an entire city’s outdoor cat population.
Cats on the loose
Loose cats are commonplace in Washington, DC, which has 200,000 felines. Like many cities, Washington has had its share of cat management controversies.
Professionals on both sides of the loose cat debate largely agree that cats are safest when kept indoors. The lifespan of an outdoor cat usually peaks around 5 years, compared to 10 to 15 years for an indoor cat. Loose cats face many threats, including collisions with vehicles and contact with rat poison. Recognizing these risks, most animal welfare organizations encourage an indoor-only lifestyle.
Similarly, there is little disagreement that cats hunt; for centuries humans have used them to control rodents. But invasive rats, which are often the target of modern rodent control, can grow too large to be easy prey for cats. In response, cats also pursue smaller species that are easier to catch. Studies have linked cats to 63 extinctions worldwide and have estimated that cats kill 12.3 billion wild mammals each year in the United States alone.
Disagreements arise around the handling of cats that already live outdoors. Population management programs often use trap-neuter-return, or TNR – a process in which cats are trapped, spayed, or neutered and released back to where they were captured.
In theory, TNR limits population growth by reducing the number of kittens that will be born. In reality, it is rarely effective, since 75% of individual cats must be treated each year to reduce the population, which is often unachievable. However, reproduction itself is not what most worries conservation biologists.
Today, the Earth is losing wildlife at such a rate that many scientists believe it is experiencing its sixth mass extinction. In this context, the effects of free-roaming cats on wildlife are a serious concern. Cats have a hunting instinct, even when fed by humans. Many wildlife populations are already struggling to survive in a rapidly changing world. Falling prey to a non-native species does not help.
Cats are not picky hunters, but will pounce on the easiest prey available. This generalist predatory behavior contributes to their reputation as one of the most damaging invasive species. But in our opinion, this could also be a key to limiting their ecological impact.
Manage cats based on their behavior
Since cats are generalist predators, their wild-caught diets tend to reflect the locally available species. In areas where there are more birds than mammals, such as New Zealand, birds are the primary prey of cats. Likewise, the diets of cats in the more developed parts of cities probably reflect the most available prey species – rats.
While cats top the list of harmful invasive species, rats aren’t far behind. In cities, rats spread disease, contaminate food and damage infrastructure. There aren’t many downsides to free-roaming cats preying on rats.
Downtowns have no shortage of rats, which can live anywhere, including parks, subways, sewers, and buildings. But native animals tend to stay in or near areas with sufficient outdoor habitat, such as parks and wooded neighborhoods. When cats hunt in these same spaces, they pose a threat to native wildlife. But if cats don’t share these spaces with native species, the risk goes down significantly.
Funding for conservation is limited, so choosing effective strategies is essential. The traditional approach to cat management has largely been to attempt to ban cats from being loose altogether – an approach incredibly unpopular with people who care for outdoor cats. Despite calls for outdoor cat bans, few have been enacted.
Instead, we suggest prioritizing areas where wildlife is most at risk. For example, cities could create “cat-free zones” near urban habitats, which would prohibit the release of trap-neuter-return cats into these areas and impose fines on owners of these areas who let their cats roam around. the outside.
In Washington, DC, that would include wooded neighborhoods like Palisades or Buena Vista, as well as homes near parks like Rock Creek. In our view, this targeted approach would have more impact than the unpopular and difficult to enforce citywide ban on outdoor cats.
Radical policies have done little to reduce outdoor cat populations in the United States. Instead, we believe a data-driven, targeted approach to cat management is a more effective way to protect wildlife.
[Understand new developments in science, health and technology, each week. Subscribe to The Conversation’s science newsletter.]