National Geographic Daily News
A housecat stalks turkeys.

A domestic cat stalks turkeys in Maine.

Photograph by Bill Curtsinger, National Geographic

Katia Andreassi

for National Geographic News

Published January 29, 2013

Maybe the butler didn't do it. But the cat probably did.

A new study, published January 29 in Nature Communications, estimates that cats are responsible for killing billions of birds and mammals in the continental U.S. every year. The estimate: 1.4 billion to 3.7 billion bird victims and 6.9 billion to 20.7 billion mammals. Peter Marra, the senior author of the study, called the results "stunning." (Watch: A house cat's point of view.)

"For the last 20, 30, 40 years," he said, "the number that has been batted around as a max was about 500 million."

And there are a lot of potential feline killers. Over 80 million pet cats reside in American homes and as many as 80 million more stray and feral cats survive outside.

The authors found that the stray and feral cats are responsible for most of the kills. But pets aren't exactly innocent: They are blamed for about a third of the bird action. The study also discovered that the cats mainly kill native species like chipmunks and house wrens, not invasive pests like the Norway rat (Rattus norvegicus). (Video: Secret lives of cats.)

The study is part of a larger effort to quantify the threats to birds, said Marra, an ecologist with the Migratory Bird Center at the Smithsonian Conservation Biology Institute in Washington, D.C. Cats happened to be the first threat they considered. Plans are to look at other threats related to human activity: wind turbines, buildings, automobiles, and pesticides. The research is important, Marra said, because "a lot of these causes of mortality may be reversible." He hopes the study will aid policymakers and help cat owners realize "cats are having a larger impact than we thought."

So what can be done about all these wild killer cats?

Current efforts to rein in America's feral cats are insufficient. While a feral cat management technique called Trap-Neuter-Return (TNR) stops some cats from reproducing, it doesn't stop those cats from preying on wildlife. The Humane Society of the United States supports TNR as part of the solution, but acknowledges that it will not noticeably reduce the cat population. John Hadidian, a senior scientist with the society, notes that TNR only reaches about two million cats, and it can be "cumbersome and expensive." He hopes that the attention from papers like this will encourage novel approaches like oral contraceptives for cats.

To some cat observers, the study news was no surprise. Economist Gareth Morgan made headlines around the world last week when he launched a proposal to rid New Zealand of cats. Morgan, whose website features a cartoon kitten announcing "I love to kill," believes that pet cats are endangering New Zealand's birds. While his website advocates a New Zealand without cats, and he would like people to make their current cat their last, he says he really wants cats to be regulated the way dogs are. He points to laws enacted in Western Australia as an example: Cats must be registered, neutered, and microchipped. The microchip, a small identifying device embedded under the skin, can be detected by vets or authorities so they can reunite lost pets with their owners and differentiate between pets and strays. "I'm not saying they should kill their cats," Morgan said. "If they are really into cats, that's fine, but you must control them."

Morgan admits this is "an emotional issue" in a country where nearly half of the households have at least one feline. "It's not that cat owners don't care," Morgan said, "it's that they haven't thought about it."

Meanwhile, people in the U.S. aren't likely to turn on cats either. Cat ownership has increased from about 56 million pet cats in the mid-1990s to the current count of 80 million. Though cats are viewed as both a conservation threat and a human companion, the Humane Society's Hadidian thinks common ground can be reached. "Both the bird people and the cat people want the same thing," he said, "fewer cats outdoors."

34 comments
Jeremy Briggs
Jeremy Briggs

All the ignorant rants fanatically in favor of letting domestic cats run rampant may be infected, in their brains, by toxiplasmosis http://en.wikipedia.org/wiki/Toxoplasmosis

Or perhaps they don't know about the study that shows that cats increase populations of the invasive house mouse, while decimating our native mice in North America, which tend to be less pestilent.

And the many, many studies on birds and chipmunks and many other small mammals. 

Fight the brainwash of them little parasites in your brain!

Nature is out of balance, largely to the elimination of top predators. Don't want wolves? Hello, coyote. Too many deer? Hello, tick overpopulation. It goes on and on… web to web. Nature repairs itself any way it has to. It's time we listened instead of dictating.


Meredith B.
Meredith B.

No offense, but this is rediculous Cats are cats. They eat birds. DEAL WITH IT PEOPLE!!! Farrel and pet cats are not going to be the end of an entire species.  And why are people picking on cats? I don't see a group trying to end dogs chasing squirrels or parrets talking! Hunting is what cats do. #angry     >:(

Dima Appleseed
Dima Appleseed

The bird brained people just pull these figures out of thin air...so frustrating...


Fuzzy math on cats, birds clouds highly questionable ‘study’January 31, 2013 - By Francis Battista - ( 17 Comments )

Did you see it? It was all over the Internet the last couple of days. Sound the alarm, alert the news media. Reportedly, cats are stone-cold killers to the tune of possibly 19 billion animals a year!

USA Today, the New York Times, NPR and just about everybody else have been reporting on a “study,” released in the journal Nature Communications, that claims startling new estimates for the number of prey captured each year by free-roaming and feral cats.

The report, “The impact of free-ranging domestic cats on wildlife of the United States,” unfortunately relies on the agenda-driven analysis of its authors and is devoid of any critical assessment of source material or common-sense implications of its claims.

This particular “study” was designed for one purpose and one purpose only: to directly attack non-lethal programs for outdoor cats and all who support them. It contains no new information and includes estimates from studies dating back 75 years.

While the authors themselves dismiss some of these studies, they nevertheless proceed to use them, along with other source material mathematically extrapolated from the perceived hunting habits of a dozen well-fed house cats. Seriously, that is the extent of some of the research that produced these numbers.

The report claims, for example, that cats kill up to 3.7 billion birds. One has to ask why the only bird deaths that seem to matter are those that are — when combined with misrepresentation and bad math — attributed to cats. Cats do not fly by the way!!!!!!!!!!!!!!

Where are the studies surrounding the annual number of birds killed by sport hunters, pest control or pollution? And, although there has been some work done regarding birds killed by wind turbines, cell phone towers and window strikes, this information lacks the concerted public opinion manipulation that is so evident in this “war on cats and all who love them.”

The “concern” by academics towards the death of wildlife is equally suspect. According to the report, cats kill more than 12 billion small mammals per year — mostly mice, moles, squirrels and shrews. Such a figure would suggest that squirrels (not to mention mice and other rodents) are on the verge of extinction — obviously nonsense to anyone who lives near any city park.

Where are the studies and scientific analysis surrounding the number of rodents killed by poisons intentionally set under kitchen sinks? What about those vicious and equally indefensible glue or mole traps? How about the millions of squirrels killed or maimed annually by hunters or children who gleefully discover their first BB gun under the Christmas tree?

But there is a larger point here. You would think that cat advocates and wildlife biologists (sometimes one and the same person) should all want the same thing — to stabilize and reduce the numbers of stray and free-roaming cats across the country. The difference is in how to get there.

Let’s face it. The authors and the anti-free-roaming cat contingent want stray and feral cats to be rounded up and killed, plain and simple. They want this in spite of the fact that this standard approach to controlling outdoor cat populations has been deemed cruel, cost-prohibitive, inefficient and generally unacceptable to the pet-loving public.

In truth, no one actually knows how many free-roaming cats there are in this country, which makes it impossible — and frankly irresponsible — to pull a number out of the air and multiply it by a theoretical number of birds that the average cat supposedly kills each day. This is especially true when the number is derived in part from observing chubby house cats.

Trap/neuter/return, or TNR, which the authors dismiss, is a proven and humane method for reducing the number of community cats. TNR involves trapping, neutering and releasing community cats back to their colonies. Sterile cats obviously can’t reproduce, and, over time, TNR reduces the number of free-roaming cats in the target colony.

If the number of community cats continues to grow, it means that TNR is not being practiced as widely as it should be. Meanwhile, individuals, such as the report’s authors, keep recycling and repackaging the same discredited information.

Let’s face it, scapegoating cats is a huge and, sadly, lucrative business. If even half the U.S. Fish and Wildlife’s energy and funding was geared toward spay/neuter and educational programs, this problem wouldn’t be an issue. But, that, of course, would result in a lot of well-connected, taxpayer-reliant academics being forced out of work.

This latest misguided ”study” is nothing more than a calculated effort to block the universal endorsement of a sound, humane population management strategy for cats that has been successful in municipalities across the country.

One more reason for this stupid stupid comments (how does National Geographic even allow these comments) is that Counties rather than using the humane ways of TNR prefer to shoot, poison torture cats so they can fatten their own pockets

Ddoes National Gepgraphic know that Koreans and Chinese both boil kittens live to eat them?????????

GOD WILL INTERVENE to stop this evil behavior, that is for sure

Scott Lawson
Scott Lawson

Cats? Really, Humans by far are the most efficient species at killing on the planet 

Dea Hysa
Dea Hysa

Well done America..Just when I thought you couldn't surprise me with anymore bs.

First Last
First Last

Saying that "the cats mainly kill native species like chipmunks and house wrens, not invasive pests" overstates the case: cats also kill House Sparrows (Passer domesticus), which are a non-native, invasive species, not to mention a fair number of native pests. I have personally witnessed a cat killing and eating a gopher that I had been unable to get rid of.

Jerrie Prater
Jerrie Prater

If you own a cat, (I Do) spay or neuter, and do not let your cat out of the house unless supervised. ever.. you can train them to walk on leash or use a catio. Cats shouldn't roam if only for their own saftey


Nancy Mcgrath
Nancy Mcgrath

This story is going to cause more cat death. These animals have suffered because of man.How about a counter number of how many birds are killed from pesticides? Every house that sports a little" do not enter,pesticide lawn appication" is more cause for bird death and sickness. Silent spring is still going on. Spay and neuter is the message that should be sent,not this ! How about something simple like break away collars with loud bells rather than a death sentence!!

Bettina B.
Bettina B.

How about training? To a certain extent, you can teach a cat what kind of pray is OK (mouse) and what isn't (bird).

Michelle Ali
Michelle Ali

I am a proud cat lover and owner and have been for years. The thought of losing them over all of this is madness. It is the circle of life. Kill or be killed! Survival of the fittest and cats are way ahead in the stakes. Don't start mass-culling of these beautiful creatures because you'll only mess with natures food chain. Yes to cats (and all animals!) and No to stupid people!

John C.
John C.

All the single female Obama voters are going to go nuts.

Jim Roberts
Jim Roberts

The creatures that cats kill and eat, are mostly rodents that humans consider a threat to humans.  So, a boring day in the news room caused the news media seize an opportunity to bad mouth cats, for doing us all a favor.  I do not recall a single incidence when a house cat [ever] killed a human.  They will cause an a**wipe human substantial injury while escaping from that human who tries to do the cat harm.  Beyond self defense, I am unaware of any evidence of any human being injured or killed by a cat.

Ben Vincent
Ben Vincent

Between cats and wind turbines birds are having it pretty bad.

Sidney Cooper
Sidney Cooper

Not really surprising.  Cats are predators.  They pretty much kill anything smaller than them - including us!

Kevin W
Kevin W

 It sounds like the only people that are in denial are the cat people. I for one am sick of the neighborhood cats leaving dead chipmunks on my back patio. They also keep spraying my patio furniture and back door. In the summer I enjoy sitting on my patio and reading. Though I can't really enjoy it anymore because after about a half hour of sitting in a cat urine soaked chair I get a headache from the horrible smell of cat urine.

   I chased one of the cats off and actually watched it leave my yard and run through a pet door in my neighbors back door. The one time my dog got out and defecated in her back yard she had a s*** fit! Actually, I think it was when my dog peed on her mailbox. Anyway, I brought the cat pee up and her excuse was that cats are free spirited creatures. Well, next time I might just be target practicing with my pellet gun in the back yard, and the cat my just FREELY walk in front of it!

Barb Williams
Barb Williams

If there were no cats, the rats would be eating the bird's eggs.  We are better off with the cats.

Agurus Guru
Agurus Guru

Estimates based on "poof".  Math like Obama uses.

S.w. Tsang
S.w. Tsang

@Chuck Hansen don't tell it to national geo and all those birders or at uk they call them twitchers ! obsessed and live for birds only and see nothing else in nature ! maybe their hunting dogs or their swiss bank accounts inherited from their daddies .

S.w. Tsang
S.w. Tsang

@Dima Appleseed national goe loves dogs even features dogs all the time in their national geo wild channel. go figure it out? dogs are domestic pets. so why have them daily on its channel for wild animals at all like the dog whisperer, dog town , alpha dog , blue collar dogs, next thing u know it will have a show on sex with dogs ! marriage to dogs !

Scott Lawson
Scott Lawson

At least cats normally pick there battles with some purpose. Us on the other hand just go gung ho and kill everything!!


S.w. Tsang
S.w. Tsang

@Jerrie Prater  u are so right. keep your cats indoor, if they are let out, supervise them. after all , they have an i.q = to a 2 yr old human kid ! and shame on those who dump their unwanted pets ( kittens and cats ) out on streets and parks ! take them to the shelters ! it's cruel. how do u think we have feral or strays? cats did not swim all the way from africa to here !  dogs too are invasive species and kill for fun especially in a pack ! other invasive also ruin the eco system; but we do not want to mention and that is -  goats, cows, horses, chickens - thanks to our love of meat and agri business ! they do demonize pigs. again, they did not want to be food animals, definitely the female pigs do NOT want to be in a gestation cage so small that the poor animals can't turn around. and often these animals are beaten or even rape!

Mike McMillian
Mike McMillian

@Michelle Ali Your comments make you sound like one of the stupid uneducated people you write about. Do a little research before you babble such drivel. Cats are threatening wildlife at an alarming rate so your last sentence makes no sense. Your cats if they are outdoor cats are killing more wildlife than you know. Cats do not belong in any habitat in the world. They are the exotics. Try to read a little next time.

S.w. Tsang
S.w. Tsang

@Jim Roberts humans have been attacked and human babies have been killed by family dogs for no reason that we know of. but a dog rescue group attempted to rescue the poor even the owner had decided to put the dog to sleep inhumanely. judge was on the side of the grieving father. 

S.w. Tsang
S.w. Tsang

@Sidney Cooper like all predators. if humans were as small as cats, do u think dogs would be your best friends. 


we are the biggest and badest predators of all . and we have a brain, a big one with big guns , bombs and lies! we know better than cats , have yet to act better

S.w. Tsang
S.w. Tsang

@Kevin W adocating violence and animal cruelty ? the one u should aim at is the cat's stupid owner ! she is stupid and dumb !

Mike McMillian
Mike McMillian

@Agurus Guru Do some research before you blow this study off. There are plenty more to back it up. Cats are killing wildlife at an alarming rate, especially feral cats. Have your cat fixed before it's first litter and keep them indoors. That will help.

S.w. Tsang
S.w. Tsang

@Mike McMillian @Michelle Ali  neither do dogs which are truly invasive why? because men have captured and bred wolves into dogs !  so dogs do not belong to any where and invasive to the world. yet they do kill at our blessing why? because their masters are hunters , poachers and illegal wide animal traders and canned hunting farm owners and professional hunters. lastly some family dogs do kill their family members about 24 people per year. just last year a new born baby was kill by the family dog. dogs do not have a killer bite, they just bite and tear u till u die or stop moving or dog has lost interest

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