Smithsonian Study Finds Cats in U.S. Kill Billions of Birds and Mammals

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PARIS - Domestic cats in the United States kill up to 3.7 billion birds and as many as 20.7 billion mice, voles and other small mammals each year, biologists estimated on Tuesday.

Puss is probably the biggest human-induced killer of these species, outstripping better-known culprits such as habitat loss, agricultural chemicals or hunting, they said in a study published in the journal Nature Communications.

A team led by Scott Loss at the Smithsonian Conservation Biology Institute in Washington looked at published research into the predation habits of cats.

Cats that have outdoors access kill between 30 and 47 birds apiece in temperate parts of Europe and North America each year, and between 177 and 299 mammals, according to past investigations.

The next step was to get an estimate of the number of cats in the United States.

Loss's team calculated there were around 84 million cats with owners, of which a couple of million are unlikely to have outdoor access or go hunting.

Added to that are between 30 and 80 million "unowned" cats -- animals that are wild or free-ranging but without an owner and survive on goodwill.

"We estimate that free-ranging domestic cats kill 1.4 to 3.7 billion birds and 6.9 to 20.7 billion mammals annually," says the study.

"Unowned cats, as opposed to owned pets, cause the majority of this mortality."

The paper says the estimates are much bigger than previously thought, and show that cats "are likely the single greatest source of anthropogenic [man-made] mortality for US birds and mammals."

It adds: "Scientifically sound conservation and policy intervention [are] needed to reduce this impact."

The study tried to get a fix on the numbers of reptiles and amphibians that are killed by cats, but drew a blank.

According to the famous "Red List" compiled by the/ International Union for Conservation of Nature (IUCN), cats on islands have caused or contributed to the extinctions of 33 species of birds, mammals and reptiles.

The study coincides with a fierce debate in New Zealand, where Gareth Morgan, a businessman turned philanthropist, has called for cats there to be eradicated to save the country's unique species of wildlife, which includes the flightless kiwi.


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When we moved here from Germany, we had two cats, two-year-old litter mates, who had always been purely indoor cats. I built a cat door so that they could go in and out at will...and the killing began. Within a few months I'd lost count after three dozen birds and about forty mice and rats. Sometimes we'll go a couple of weeks with no kills (at least none they bring into the house to finish off), other times it can be one or two a day.
Our cats are well-fed, happy, and affectionate, five-year-old killing machines. It is their nature, cats are predators and much more feral than domesticated dogs. I'm pretty convinced they would kill us too except 1) we feed them, and 2) we're way too big. I still love both kitties, I'm a life-long cat "owner" and will be forever.

January 08 2014 at 11:24 PM Report abuse rate up rate down Reply
Tracylea Byford

Let's see. This Smithsonian "farce" that is pretending to be a serious study finds that cats are causing species to vanish. Human beings by their habitat encroachments are causing species to vanish. Outdoor cats should be killed to solve the problem. So, by inference, one could argue that the Smithsonian believes a viable solution to human encroachment would be to kill humans to solve the problem? Wake up folks and boycott the Smithsonian. Who knows what their next "study" will find, or recommend. Brrrr. Chilling.

February 26 2013 at 8:10 PM Report abuse rate up rate down Reply
Tracylea Byford

Let's see. Cats are causing species to disappear. Human encroachment is causing species to disappear. The Smithsonian "farce" that is pretending to be a serious study advocates for killing cats because they are contributing to vanishing wildlife. Does it then by inference, advocate killing humans for same?

Boycott the Smithsonian, folks. Before they go any further...

February 26 2013 at 8:06 PM Report abuse rate up rate down Reply

You are simply taking this study at face value? A study which used only 69 birds and very sloppy statistics?

I don't think that is caring about cats, or truth.

February 07 2013 at 9:05 PM Report abuse rate up rate down Reply

What, no critical thinking about this study, which extrapolated from 69 bird studied? ONLY 69 birds, and sloppy science and misleading statistics?

Way to stick up for cats, she said sarcastically.

February 07 2013 at 9:04 PM Report abuse rate up rate down Reply

It is an ESTIMATION based on quantitative analyses. An ESTIMATION. No actual proof, just estimates on what they THINK cats kill, based on other junk science that uses fake calculators to estimate, without actually trying to actually get data from shelters in study areas. According to their calculator, there are over 30,000 ferals in my city. Luckily, we have tons of bleeding-heart programs that attend to feral cats as quickly as possible, and the actual number of ferals estimated by professional feral caretakers are around 10,000. I am so sick of people trying to blame cats for behaving like cats. Why not go after the fools who carelessly let their unfixed cats outside, letting them get pregnant, then putting them out because they can't deal with THEIR mistake? Species die every single day, and new species are found every single day. It is the way of life! Let me tell you, birds reproduce MORE than cats do, to believe birds are in danger is ridiculous.

February 02 2013 at 3:10 PM Report abuse rate up rate down Reply
Deborah Ripoli

you are freaking kidding me! no one will allow for cats to be eliminated. every animal kills off another. that is part of nature. I would say pollution kills more birds than cats do. nothing like putting the thought out there for people to abuse cats.

January 30 2013 at 9:38 AM Report abuse rate up rate down Reply
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