Free-ranging cats are an invasive species and a threat to themselves, scientists say

A free-roaming cat is not a happy cat. According to a new study in the journal Frontiers in Ecology and Evolution, free-ranging house cats are a downright threat to native wildlife — largely because of the irresponsibility of their human owners. The new research adds to an ever-growing literature on how mankind’s love for cats is transforming the natural world.

“Cats are like a grenade for hunting when a bullet would do. Cats kill everything they can. They don’t target specific species.”

This particular study was conducted by American and Canadian researchers who used a camera trap survey to examine the interactions of free-ranging house cats in the Washington, DC area over a three-year period.

The scientists also analyzed the interactions of eight native mammalian species, five of which are commonly preyed on by cats and three of which are notorious disease vectors. They found that where there are more people, there are more likely to be cats — and where there are more cats, cats are more likely to interact with disease-carrying mammals like raccoons and red foxes. In addition, where there are more cats, there are white-footed mice and eastern cottontails, which are preyed upon by feral cats.

“Our research was driven by a desire to inform more effective and humane outdoor cat population management practices to protect cats and wildlife alike,” Daniel Joseph Herrera, a graduate student studying urban ecology at the University of Maryland-College Park, told Salon by E-mail. Interestingly, the study also debunked certain myths about house cats, namely the notion that they are nocturnal. Rather, the researchers found that “Instead of having peaks of activity at night (nocturnal) or during the day (diurnal), cats — as a species — maintained a relatively constant level of activity throughout the 24-hour day. In other words, our analysis revealed that cats have no clear pattern of activity and individual waking times vary widely and overlap.”

This means that when humans begin to populate a community and allow their cats to roam freely, chances are high that the cats will interact with wildlife in that area – everything.


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“From a management perspective, this means that conflicting patterns of activity cannot be relied on to end the cat-wildlife conflict,” Herrera pointed out. “Taking measures to ensure cats and wild animals are not in the same space, e.g. B. Keeping cats indoors will prove more effective.”

Bird watchers are certainly inclined to agree with Herrera’s argument. Grant Sizemore, director of invasive species programs at the American Bird Conservancy, was quick to challenge the misconception that cats need or deserve to roam outdoors to be happy and healthy.

“On the contrary, cats who exercise outdoors are exposed to a variety of serious risks, including vehicle traffic, poisons, injuries and illness,” Sizemore explained via email. “Cats with outdoor access are almost three times more likely to be infected with parasites,” Sizemore said, citing a 2019 study from Biology Letters. Keeping house cats indoors, in an outdoor enclosure, or on a leash. Indoor cats can live long and happy lives.”

“If cats are dependent on humans, then whatever hunts they engage in is not ‘natural’ in that humans have facilitated it… They don’t serve an ecological role, they do ecological harm.”

Sizemore also debunked the notion that cats do not have a significant impact on their local environment when preying on native creatures.

“Not only are domestic cats not native to the United States and therefore not a natural part of the environment, their predatory impact can be significant,” Sizemore noted. “Kays et al. (2020) found that the impact of domestic cats is actually 4 to 10 times greater than that of domestic predators, partly due to the incredibly high density of cats. In the United States, an estimated 2.4 billion people are killed by free-ranging birds each year.” As a result, “domestic cats have already contributed to the extinction of 63 species of birds, mammals, and reptiles, and domestic cats are the leading source of direct human-caused avian mortality in the U.S.”

All of Sizemore’s points are based on older research – but the Frontiers in Ecology and Evolution study reinforces these points.

“Proponents of free-roaming cats often claim that cats are merely entering into a vacated ecological role,” Herrera pointed out. “An interesting finding of our study is that cats are positively associated with human development, while wild animals are more negatively associated with dense human development. This finding implies that cats depend on humans for their survival, but wild animals do not.” This suggests that cats depend on humans to survive in densities common in urban areas. “If cats are dependent on humans, then any hunt they do isn’t ‘natural,’ since humans have facilitated it.” Worse, cats hunt wildlife far more often than native species, meaning that “they don’t have an ecological role fulfil, but cause ecological damage”.

They could also help start another pandemic.

“The human-cat relationship further complicates ecological interactions such as transmission of zoonoses,” Herrera noted. “While a human would never knowingly open their doors to a rabid raccoon, pet cat owners routinely allow their cats to engage in activities where they could contract rabies, and then welcome them back into their homes at the end of the day.” Cats in particular can harbor SARS-CoV-2, the virus that causes COVID-19. Epidemiologists know that the more a virus crosses between species, the more opportunities it has to mutate. SARS-CoV-2 is thought to have originated in bats and pangolins before spreading to humans.

Stephen Vantassel, a vertebrate pest specialist at the Montana Department of Agriculture, was more succinct in his analysis.

“People think, ‘The cat only kills unwanted rodents. I need the cat to control bugs,'” Vantassel wrote to Salon. “Answer: Cats are like using a grenade for hunting when a bullet would suffice. Cats kill everything they can. They don’t target specific species.”

As for the idea that a cat needs to go outside for their sanity? “No. Indoor cats can have toys and play if you take the time. Their health will improve as well,” Vantassel said.

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