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Cats Kill Billions of Small Animals Per Year, Study Shows


Feral or domesticated, cats are wreaking havoc on the populations of chirpy birds, chubby-cheeked chipmunks and cuddly rabbits, according to a new study.

Researchers were astounded to discover that the toll wrought by the nation’s 160 million cats—half of them pets and half wild—reaches into the billions.

Peter Marra, an ecologist at the Migratory Bird Center of the Smithsonian Conservation Biology Institute out of Washington D.C. and a senior author of the paper, was studying cats in the context of learning what the biggest threats to birds are, according to National Geographic. To find out how many animals cats kill annually, he and his team extrapolated using data from various local studies and surveys, The New York Times said. Marra, colleague Scott R. Loss and a researcher from the U.S. Fish and Wildlife Service, Tom Will, published their findings in the January 29 issue of the journal Nature Communications.

"For the last 20, 30, 40 years, the number that has been batted around as a max was about 500 million,” Marra told National Geographic, and said to The New York Times. “When we ran the model, we didn’t know what to expect. We were absolutely stunned by the results.”

What they found was that feral cats and outdoor cats kill 1.4 billion to 3.7 billion birds and 6.9 billion to 20.7 billion small mammals, reported. Most of them are killed by feral cats, though a third of the critters are offed by outdoor kitties. Most of the victims are small mammals such as shrews, chipmunk and voles, The New York Times said. Further, cats do not hunt invasive species such as the Norway rat, but seem to prefer the other, native species. 

Cats themselves are an invasive species of sorts, having originated in Asia and Africa, domesticated themselves via symbiotic relationship with newly agricultural peoples thousands of years ago, and then come over to Turtle Island with the settlers, according to Leslie Lyons, a researcher studying cat genetics at the University of California’s Davis School of Veterinary Medicine. 

“There is archaeological and genetic evidence to show that cats first originated in the fertile crescent,” Lyons told the Associated Press in 2008. “We took genetic samples in Egypt, Turkey, Lebanon and Iran, and they are all tied together because that was the seat of cat domestication.”

While the bond that ancient Egyptians had with cats is well known, lesser known is how they got here.

“Cats spread through Asia, where they also became important to societies there: An all-white cat is considered good luck, for example,” Lyons told AP. “They came here, to North America, with the Pilgrims, on the boats to help with the rodent populations. There are no domesticated cats that are indigenous to America or Australia, they all came over on boats.”

Today, feral cats abound in Indian country, with thousands roaming the Navajo Nation alone, according to Rescue Operations of Animals on the Reservation, a Flagstaff, Arizona-based nonprofit group that works to reduce the number of strays on Indian reservations. 

The subject of rogue kitties has been swirling around lately, with New Zealand environmentalist Gareth Morgan's suggestion last week that homeless cats be put down and pet cats kept indoors. Though Trap-Neuter-Release (TNR) programs reduce reproduction, the cats still kill, as John Hadidian, a senior scientist with the Humane Society of the United States, pointed out to National Geographic. And regardless of how they arrived, the Smithsonian scientists said that something must be done. 

“Our findings suggest that free-ranging cats cause substantially greater wildlife mortality than previously thought and are likely the single greatest source of anthropogenic mortality for US birds and mammals,” the authors said in their abstract. “Scientifically sound conservation and policy intervention is needed to reduce this impact.”