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How Outdoor Cats Impact The Environment

Updated on January 1, 2017
Bob Bamberg profile image

Bob has been in the pet supply business and writing about pets, livestock, and wildlife in a career that spans three decades.


My friends at the trade publication, Pet Product News International are about more than just pet products. I consider them a valuable watchdog agency because they alert me to a variety of animal related issues that usually aren’t reported by the mainstream media.

A case in point is the March, 2013 edition where Clay Jackson reports on a study published in January by the journal Nature Communications. The study was conducted by Peter Marra and Scott Loss of the Smithsonian Conservation Biology Institute and Tom Will of the U.S. Fish and Wildlife Service’s Division of Migratory Birds.

These guys pored over some 90 studies on cat predation to come up with some eye-popping numbers, and a war of words between some conservation and advocacy organizations.

When you’re talking about cats, you’re touching a raw nerve among a lot of folks, and when you’re talking about the victims in this report, you’re dealing with a house divided. First, let’s look at the study’s key finding.

Expressed in median figures, the study revealed that some 2.4 billion (yes, with a “b”) birds are killed each year by felis catus, the cat. I wonder if that’s where star of film and print Felix The Cat got his name. But I digress.


If you think that’s a big number, how would you like to be a small mammal such as a mouse, a vole, a squirrel or a rabbit?

In the United States alone, cats that roam freely kill some 12.3 billion of them each year. The fact that these species are such prolific breeders is nature's way of compensating them for being a prey animal.

While backyard cats are acknowledged as significant contributors to these stats, the study reports that 80 million farm cats, strays and ferals are responsible for 69% of bird mortality and 89% of mammal mortality.

OK, let’s break out the gloves.

In This Corner...

Washington, D.C. is home to the American Bird Conservancy, and its president, George Fenwick, Ph.D., was quoted in the report thusly: “This study…demonstrates that the issue of cat predation on birds and mammals is an even bigger environmental and ecological threat that we thought.”

And in This Corner...

Just up the road a piece, in Bethesda, Maryland, is the cat advocacy group Alley Cat Allies. Their president, Becky Robinson, said the findings were “part of the continuing propaganda to vilify feral cats,” adding that the study was “bad science” and “a veiled promotion by bird advocates to ramp up the mass-killing of outdoor cats.”

Are the Average Joe and Jane Hypocrites?

Veering off course just a bit, away from the study, I’d like to insert a personal observation. Some of the victims…the small mammals…are also victims of a double standard.

If the study reported on just the birds that were being killed by outdoor cats, me thinks that news would be enough to sound the alarm.

But, what if the study just reported on the mammals that were being killed by outdoor cats?

I submit that the only sound to be heard would be a collective yawn, or perhaps some cheering.

The mammals are considered by most to be pesky vermin. Even the rabbits, which decimate vegetable gardens all across the U.S.A.

But, even pesky vermin have a niche; an important role in environmental affairs.


The study’s authors acknowledged that matters of the heart oft times trump objective science when they concluded: “Despite these harmful effects, policies for management of free-ranging cat populations and regulation of pet ownership behaviors are dictated by animal welfare issues rather than ecological impacts.”

But wait a minute you scientists; doesn’t this quote make sense: “Because of the success of TNR (trap-neuter-release), which stabilizes then reduces the population; places where there were once large colonies of feral cats have seen those colonies fade away.” That quote came from Alley Cat Allies’ Robinson.


It's possible that some cientists might dismiss the quote as anecdotal and question how many birds and mammals would be killed while the colony is fading away.

I'll bet that would make for a most interesting study.

After looking at how many birds are killed annually, by a variety of causes, one has to wonder how long it will be before we run out of birds.

If only birds were as prolific breeders as small mammals are.

We'd pretty much be assured of a never-ending population of them.

Do You Find The number of Birds Killed Disturbing?

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Do You Find The Number of Small Mammals Killed Disturbing?

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How Would You Deal With The Stray/Feral Cat Situation

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    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts

      Not bad for an old guy! Great to hear from you and to catch up. I see Mike Murphy from time to time. He's been retired for 4 years or so and looks great. Except for the grey hair, he hasn't changed any. Other than that, I don't see the old crowd anymore.

      As far as I know, Frank T is into his 80's and still coming down for breakfast. Newt, from Cooper's, who's well into his 80's and sharp as a tack, gets a phone call from him around Christmas each year.

    • Billrrrr profile image

      Bill Russo 

      6 years ago from Cape Cod

      Hi Bob. Yessir. It's me. Turning 70 in November and still kicking and still up for the "gigs"!!!

    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts can't be...but it must be...or in today's parlance, this the Billrrr whose mother-in-law launched my broadcasting career from her position as a nurse's aide at Choate Hospital in Woburn...the Billrrr with whom Don, Charlie, Joe's Kid and I went to the "gigs" at Jack Witchi's every Friday night...the Billrrr with whom the Barrington Bomber, the Cranston Crusher, the Knott St. Knocker and I would compete the next day at North Bowl...the Billrrr who taught me the finer points of handicapping greyhounds...the Billrrr with whom I shared a million laughs at WARA?

      Great to see you, Bill. Funny, but I was having one of those "I wonder whatever happened to" moments recently and you crossed my mind. After 40-odd years, it's good to see that we've both landed on our feet!

      Thanks for commenting on the hub. Contemporary wisdom is that all cats should be indoor cats...but the reasons cited are almost always for the health and safety of the cat. The cats' impact on the environment is sometimes mentioned, but seemingly as an afterthought.

      Indoor cats do live longer than outdoor cats, though. The life expectancy of an outdoor cat has been estimated by various smart people to be less than six years, while indoor cats live to almost 20. I'm basically an indoor cat and I've made it to 66 (or +/- 14 in cat years) so far.

      I've got to run out to work...I've got 3 part time jobs to keep me off the streets and out of trouble...but I plan to zip over to your profile page and catch up on your hubs.

      Thanks for making my day! Regards, Bob

    • Billrrrr profile image

      Bill Russo 

      6 years ago from Cape Cod

      Hello Bob. This is a voice from your past. Glad to see that you have come to Hubpages. Best of luck to you. I have had eight cats in my lifetime and they were outdoor cats. I thought that all cats should be allowed to roam free. But the years have changed my mind. I have seen too many birds, squirrels and other animals killed by my beloved felines. I now believe that cats should be indoor companions only. Since my last cat passed away my Cape Cod yard has suddenly become a haven for cottontail bunnies so tame they come within two feet of me. Cardinals abound near my feeders. Mourning Doves greet me at the back door every morning. I know how hard it is to say no to a cat that is begging to go outside, but it needs to be done.

    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts

      Hi Jaye, great seeing you again. You make a lot of valid points. Where I live (small city) the majority of cat owners maintain them as indoor cats, but there are a number of them that let their cats roam their peril. Those folks are sort of looked down upon.

      There is the faction that believes cats are supposed to be's unnatural to keep them housebound...but they're sort of regarded as knuckle draggers. That's how it is here in the heavily populated northeast. I understand things are different in rural communities.

      Around here, crazy cat ladies (and men) are sometimes investigated as hoarders. Not too many years ago hoarding was treated as animal neglect or cruelty cases and prosecuted accordingly. Nowadays, it's considered a mental health issue. The animals are confiscated and the hoarder enrolled in the mental health system.

      Always nice to have you stop by and contribute to the comment stream. Thanks for the votes! Regards, Bob

    • JayeWisdom profile image

      Jaye Denman 

      6 years ago from Deep South, USA

      The reason for the enormous cat population is the huge number of un-neutered stray and feral cats churning out new litters of kittens as fast as they can do so. Too many of these cats end up in shelters or, as is the case in my neighborhood, running loose and being fed at the back door of at least one "crazy cat lady", who only contributes to the problem. (There are probably "crazy cat men", too, but I'll stick to my own experience.)

      Unfortunately, I've lived next door to the crazy cat lady for the past twelve years. She has multiple cats of her own, and she lets them run wild with no regard for her neighbors (though she chains her small dog to her back porch post). While the majority of dog owners keep their pets indoors, behind fences and comply with leash laws on walks, there's no such thoughtfulness from many cat owners. Fences don't keep out cats. If you don't want them on your property, that's just too bad! For some strange reason, the people who turn their cats loose outdoors cannot seem to understand why anyone would object to them. I don't mean to generalize, because I know there are also responsible cat owners who keep their pets indoors with litter boxes and don't let them bother other property-owners. I appreciate their thoughtfulness.

      Here's where the bird killing comes into play. My neighbor on the other side of my property turned her back yard into a sanctuary for songbirds and squirrels. The birds that eat from her numerous bird feeders fly into my yard, and I enjoy their songs and chirping. However, too many birds are killed by the cats that come here uninvited and unwanted. I routinely find clumps of feathers and stay bones left by these predatory cats.

      I also witnessed a cat raiding a bird nest in a tree behind my house. My small great-grandson saw it too, and it made him cry. Feral cats can be mean, and I've been badly scratched by one, requiring a tetanus shot. I suppose I should count myself lucky that the cat didn't have rabies.

      So I care more than a "tsk, tsk, tsk" about the situation, though I realize there's not much (if anything) I can do to rectify it. I only wish that all cat owners would ask themselves how they would like it if someone living near them let a pet boa constrictor into their yard!

      Some "Golden Rule" behavior is called for here....

      Voted Up++


    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts

      Hello, Melissa...thanks for stopping by. I replied to your comment last night and don't know what happened to it. I guess it's floating around cyberspace somewhere!

      We all have reasons to disregard organizations (and people, too) whose agendas are contrary to our beliefs. As I mentioned in the hub, sometimes you hit a raw nerve when talking about cats, and that may be the case with Alley Cat Allies. They do some good work, though. I'll bet if I took a poll, it would run in their favor between their supporters and detractors.

      I think it will be a long, long time before free roaming will be outlawed for cats. It was easy to do for dogs. They scare people, scatter trash that's put out for collection, and foul our lawns. Leash laws were easy to write.

      Other than killing birds and small mammals, about the worst thing cats do is poop in our flower beds sometimes. I doubt the general public cares more than a "Tsk, tsk, tsk" and a head shake about the birds and small mammals.

      Cats are too popular. There are more of them in American households than there are dogs. Thanks for adding to the comment stream. Regards, Bob

    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts

      Hello, Suhail, thanks for stopping by. Actually, where I live coyotes are common in suburban neighborhoods. Both of my sons lost cats to for sure and one suspected.

      When I owned my store, one of my customers lost her beloved Pomeranian to a coyote when the dog was about 20 feet away from her! They're back, they're bold, and they're a force to be reckoned with.

      This type of issue undoubtedly will spark lively debate. Thanks for your comments. Regards, Bob

    • Suhail and my dog profile image

      Suhail Zubaid aka Clark Kent 

      6 years ago from Mississauga, ON

      I have personally seen neighbourhood cats taking babies from the nest. It is a proven fact that cats kill birds. That explains why you wouldn't find nesting local birds near farms. North American forests are eerily devoid of chirruping of birds, only because of cats.

      However, I believe that there is a solution other than trapping and killing and neutering and releasing. We need to encourage top predators of the region make a comeback. This would translate into encouraging coyotes to return to where they belong. In the absence of coyotes as top predators on the eastern seaboard, we are witnessing a phenomena known as 'Meso-predator Release', i.e., taking up of the niche by 2nd or 3rd level of predators.

      Coyotes keep cats away from preying upon birds by sending a fear factor. Yes, there will be some complaints initially that coyotes are preying upon pet and farm cats, but then cats will themselves begin to stay home and avoid encountering coyotes.

      Another way to discourage cats from roaming free is setting 'Catting hounds' after them just like coonhounds after raccoon. Of course, this suggestion could be taken in a lighter vein as well :-)

      This is an awesome hub! Thank you for sharing.

    • Melissa A Smith profile image

      Melissa A Smith 

      6 years ago from New York

      Ok, simply put Alley Cat Allies are proven liars who will say anything to protect invasive cats. There comes a point where if I catch a person or entity in a certain number of lies that their opinions and information are entirely disregarded until backed up by a credible source. If you comb through their website it is widely apparent how much they couldn't care less about wildlife, so it will be a cold day down there when I put any stock into their perspectives.

      You are correct, the fact that people don't care about small mammals is horrendous. I am known by many to be an 'animal hater' for some of my opinions, then I have to remind people of their obvious speciesism. Many cat owners are just terrible people who when confronted with their pet's (uneaten) kill act like I'm holding a piece of dirt. Free-roaming needs to be illegal in most areas and the feral cat problem, I guess would vary by region, but trap and kill (or shoot) has its place.

    • DrMark1961 profile image

      Dr Mark 

      6 years ago from The Atlantic Rain Forest, Brazil

      True, cats don't intimidate many people. If you were the bird in that photo, though, being afraid of cats would be a good thing!

    • Bob Bamberg profile imageAUTHOR

      Bob Bamberg 

      6 years ago from Southeastern Massachusetts

      More often than not, anecdotal information, unfortunately, is unverifiable. Of course, my claim is strictly anecdotal.

      Dogs are required to be locked up because a lot of people are afraid of dogs. Cats, on the other hand, don't intimidate many folks. Anecdotal but pinky swear true.

      Thanks for stopping by, Doc. Your comments are always appreciated...although I don't have a study to back that up :)

    • DrMark1961 profile image

      Dr Mark 

      6 years ago from The Atlantic Rain Forest, Brazil

      Interesting article. Is that 2.4 billion for US birds alone? Imagine worldwide. I like cats but really appreciate my wild birds, lizards, and other small critters.

      This leads to another, even more controversial, subject. Why are dogs required to be locked up but so many cat owners think their cats should be free to go where they want? I really do not want my neighbors cats killing my parrots and robins, but when I mention it...Heavens! You can not lock up a cat!!! (People used to say the same thing about dogs.)

      That trap-neuter-release program is not saving many lives. Anecdotally. And we all know about the reliability of anecdotes, right?

      Voted up.


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