Cats kill 2.4 billion birds and 12 billion mammals every year in US alone

[treesparrow]

Outdoor cats: Single greatest source of human-caused mortality for birds and mammals, says new study

January 2013. A new peer-reviewed study published and authored by scientists from two of the world's leading science and wildlife organizations - the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service (FWS) - has found that bird and mammal mortality caused by outdoor cats is much higher than has been widely reported, with annual bird mortality now estimated to be 1.4 to 3.7 billion and mammal mortality likely 6.9 - 20.7 billion individuals in the US alone.

The study, which offers the most comprehensive analysis of information on the issue of outdoor cat predation, was published in the online research journal Nature Communications and is based on a review of 90 previous studies. The study was authored by Dr. Peter Marra and Scott Loss, research scientists at the Smithsonian Conservation Biology Institute and by Tom Will from the U.S. Fish and Wildlife Service's Division of Migratory Birds.

Problem is even worse than previously suspected

According to Dr. George Fenwick, President of American Bird Conservancy, one of the leading bird conservation organizations in the U.S. and a group that has called for action on this issue for many years, "This study, which employed scientifically rigorous standards for data inclusion, demonstrates that the issue of cat predation on birds and mammals is an even bigger environmental and ecological threat than we thought. No estimates of any other anthropogenic [human-caused] mortality source approach the bird mortality this study calculated for cat predation."

"To maintain the integrity of our ecosystems, we have to conserve the animals that play integral roles in those ecosystems. Every time we lose another bird species or suppress their population numbers, we're altering the very ecosystems that we depend on as humans. This issue clearly needs immediate conservation attention," he said further.

Carnage

"The very high credibility of this study should finally put to rest the misguided notions that outdoor cats represent some harmless, new component to the natural environment. The carnage that outdoor cats inflict is staggering and can no longer be ignored or dismissed. This is a wake-up call for cat owners and communities to get serious about this problem before even more ecological damage occurs," Fenwick said.

The study's estimate of bird mortality far exceeds any previously estimated U.S. figure for cats. In fact, this magnitude of mortality may exceed all other direct sources of anthropogenic bird and mammal mortality combined. Other bird mortality sources would include collisions with windows, buildings, communication towers, vehicles, and pesticide poisoning.

2.4 billion birds and 12 billion mammals killed by cats

The study estimated that the median number of birds killed by cats annually is 2.4 billion and the median number of mammals killed is 12.3 billion. About 69 percent of the bird mortality from cat predation and 89 percent of the mammal mortality was from un-owned cats. Un-owned cats are defined to include farm/barn cats, strays that are fed but not granted access to human habitations, cats in subsidized colonies, and cats that are completely feral.

Extinction cause

Free-ranging cats on islands have caused or contributed to 33 (14 percent) of the modern bird, mammal, and reptile extinctions recorded by the International Union for Conservation of Nature Red List of threatened animals and plant species.

Native species make up the majority of the birds preyed upon by cats. On average, only 33 percent of bird prey items identified to species were non-native species in 10 studies. Studies of mammals in suburban and rural areas found that 75-100 percent of mammalian prey were native mice, shrews, voles, squirrels, and rabbits, all of which serve as food sources for birds of prey such as hawks, owls, and eagles.

The study charges that, "Despite these harmful effects, policies for management of free-ranging cat populations and regulation of pet ownership behaviours are dictated by animal welfare issues rather than ecological impacts.

Projects to manage free-ranging cats, such as Trap-Neuter-Return (TNR) colonies, are potentially harmful to wildlife populations, but are implemented across the United States without widespread public knowledge, consideration of scientific evidence, or the environmental review processes typically required for actions with harmful environmental consequences."

_http://www.wildlifeextra.com/go/news/cat-birds-013.html

Yikes! This certainly seems a humongous amount of killing (assuming the numbers are truly valid). I suppose the bigger question is the predation by domestic cats causing any serious long term population declines in wild birds.

There does appear to be enough domestic cats (and also feral ones) in the US to carry out this level of predation.

There are approximately 86.4 million owned cats in the United States

_http://www.humanesociety.org/issues/pet_overpopulation/facts/pet_ownership_statistics.html

Then again it's just what cats are designed to do I suppose.

 

[mcb]

Yes, I have seen how it works right in the back yard, although no birds have been killed yet by our two cats. It's wired into the cats. It's what they do. If you have a lot of cats, you have a lot of bird hunting. For what it's worth, it is wired into the birds to escape, and they mostly seem to have the advantage.

Our two little predators are bored silly in the house -- with nothing to hunt but bugs -- and when they go out, they go after anything that moves. If I throw a stick, Bella knows where it lands just from hearing, and charges right for it. (She doesn't retrieve, though. :)) She nearly had finch for lunch last week, when she flushed one that was on the ground.

 

[Thomas Alan]

We had cats for years and they did catch birds occasionally. Mostly, though the preferred mice. Sometimes they would catch them outside, then try to bring them in to show us their trophy.

We had one cat that loved baby rabbits. To us he was a loving pet, to them he was probably a horror beyond belief. A difference in point of view I guess.

Another who liked to chase down and kill adult rabbits. At the time we saw this as a good thing since rabbits were pests in our vegetable garden.

Once one of our cats swallowed a mormon cricket. He never seemed to want to do that again after.

Birds are in many dangers in our times. The poisons people put on their lawns and crops. I read a article awhile back that wind turbines kill birds by the thousands. And of course loss of habitat.


I loved some of our cats dearly. But they are killers by nature. There are too many cats because there are too many people for this planet to support.

Mac

Edit: added line

 

[Gimpy]

This is why none of our cats is allowed outside. I've seen how bad it can get when we had barn cats on the farm growing up.

One of our mother cats used to bring us pheasants she'd killed to feed her kittens, full grown wild rabbits, and field rats. One afternoon I counted the number of beaks, and feet she left on our front porch and stopped when I hit thirty. (Song birds, most of those, though once or twice she even caught a bat.)

That was one cat. We had about fifteen. On a farm, the cats were needed to keep rats and mice down, and they did that well.

Having a house cat, its up to the people to keep kitty from devastating the environment. I do not understand people who let their cats outside to pillage, unless its a 'working cat'...one that has a definite job as a mouser.

 

[Josi]

And, then you have power lines and wind farms killing birds as well.

Tens of millions of flamingos, storks, pelicans and other migratory birds are being killed across the world when they fly into power lines, according to a new study.
http://www.nbcnews.com/id/45443549/ns/world_news-world_environment/t/report-millions-birds-killed-power-lines/#.UQiN02ez5D8

Spanish wind farms kill 6 to 18 million birds & bats a year
http://savetheeaglesinternational.org/releases/spanish-wind-farms-kill-6-to-18-million-birds-bats-a-year.html

 

[treesparrow]

Here's the abstract from the original paper,fwiw.
It does point out the important fact that most of the losses are caused by unowned cats.

The impact of free-ranging domestic cats on wildlife of the United States

Scott R. Loss,
Tom Will
& Peter P. Marra
Received
06 September 2012
Accepted
12 December 2012
Published
29 January 2013

Anthropogenic threats, such as collisions with man-made structures, vehicles, poisoning and predation by domestic pets, combine to kill billions of wildlife annually. Free-ranging domestic cats have been introduced globally and have contributed to multiple wildlife extinctions on islands.

The magnitude of mortality they cause in mainland areas remains speculative, with large-scale estimates based on non-systematic analyses and little consideration of scientific data. Here we conduct a systematic review and quantitatively estimate mortality caused by cats in the United States. We estimate that free-ranging domestic cats kill 1.4–3.7 billion birds and 6.9–20.7 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. 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. Scientifically sound conservation and policy intervention is needed to reduce this impact.

_http://www.nature.com/ncomms/journal/v4/n1/full/ncomms2380.html

The RSPCA (animal welfare organisation) in the UK suggests fitting a bell to a cat's collar to give birds warning of approaching danger. I'm not sure if this would include large ones like discarded church bells for instance. :D

 

[mcb]

Here's the abstract from the original paper,fwiw.
It does point out the important fact that most of the losses are caused by unowned cats.

The impact of free-ranging domestic cats on wildlife of the United States

Scott R. Loss,
Tom Will
& Peter P. Marra
Received
06 September 2012
Accepted
12 December 2012
Published
29 January 2013

Anthropogenic threats, such as collisions with man-made structures, vehicles, poisoning and predation by domestic pets, combine to kill billions of wildlife annually. Free-ranging domestic cats have been introduced globally and have contributed to multiple wildlife extinctions on islands.

The magnitude of mortality they cause in mainland areas remains speculative, with large-scale estimates based on non-systematic analyses and little consideration of scientific data. Here we conduct a systematic review and quantitatively estimate mortality caused by cats in the United States. We estimate that free-ranging domestic cats kill 1.4–3.7 billion birds and 6.9–20.7 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. 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. Scientifically sound conservation and policy intervention is needed to reduce this impact.

_http://www.nature.com/ncomms/journal/v4/n1/full/ncomms2380.html

The RSPCA (animal welfare organisation) in the UK suggests fitting a bell to a cat's collar to give birds warning of approaching danger. I'm not sure if this would include large ones like discarded church bells for instance. :D

Belling the cats, which are hunting to survive, would seem to shift the balance by having the cats starve instead of the birds caught and eaten. Great solution. How about something that focuses on the real problem - the human activity that created it.

 

[treesparrow]

Here's the abstract from the original paper,fwiw.
It does point out the important fact that most of the losses are caused by unowned cats.

The impact of free-ranging domestic cats on wildlife of the United States

Scott R. Loss,
Tom Will
& Peter P. Marra
Received
06 September 2012
Accepted
12 December 2012
Published
29 January 2013

Anthropogenic threats, such as collisions with man-made structures, vehicles, poisoning and predation by domestic pets, combine to kill billions of wildlife annually. Free-ranging domestic cats have been introduced globally and have contributed to multiple wildlife extinctions on islands.

The magnitude of mortality they cause in mainland areas remains speculative, with large-scale estimates based on non-systematic analyses and little consideration of scientific data. Here we conduct a systematic review and quantitatively estimate mortality caused by cats in the United States. We estimate that free-ranging domestic cats kill 1.4–3.7 billion birds and 6.9–20.7 billion mammals annually. Un-owned cats, as opposed to owned pets, cause the majority of this mortality. 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. Scientifically sound conservation and policy intervention is needed to reduce this impact.

_http://www.nature.com/ncomms/journal/v4/n1/full/ncomms2380.html

The RSPCA (animal welfare organisation) in the UK suggests fitting a bell to a cat's collar to give birds warning of approaching danger. I'm not sure if this would include large ones like discarded church bells for instance. :D

Belling the cats, which are hunting to survive, would seem to shift the balance by having the cats starve instead of the birds caught and eaten. Great solution. How about something that focuses on the real problem - the human activity that created it.

But surely belling a domesticated cat is at least a partial solution to begin with? (Perhaps I should have emphasized domesticated cats to begin with?) . Also, well looked after and well fed cats would not be 'hunting to survive' they would just be following their instincts. Or am I missing something?

Another possible solution might be to keep cats indoors in city districts for their own safety as well as for the good of wildlife as suggested here -

_http://www.calgary.ca/CSPS/ABS/Pages/Animal-Services/Keeping-cats-indoors.aspx

 

[mcb]

But surely belling a domesticated cat is at least a partial solution to begin with? (Perhaps I should have emphasized domesticated cats to begin with?) . Also, well looked after and well fed cats would not be 'hunting to survive' they would just be following their instincts. Or am I missing something?...

Did you see this at the above link:

Un-owned cats, as opposed to owned pets, cause the majority of this mortality.

So they want to put bells on them to "control" their hunting behavior.

 

[treesparrow]

But surely belling a domesticated cat is at least a partial solution to begin with? (Perhaps I should have emphasized domesticated cats to begin with?) . Also, well looked after and well fed cats would not be 'hunting to survive' they would just be following their instincts. Or am I missing something?...

Did you see this at the above link:

Un-owned cats, as opposed to owned pets, cause the majority of this mortality.

So they want to put bells on them to "control" their hunting behavior.

Yep, that's why I put it in bold. But roughly a third of all bird kills are still carried out by domesticated cats according to the report . That's 0.8 billion - still a huge and not insignificant number I think.

I don't see it as an attempt at any type of 'control' on domestic cats just simply a method to send a signal to wild birds to be alert and avoid predation.

Btw I think I'm may becoming emotionally invested in this discussion, maybe not a good thing :) Chance for self observation maybe?

 

[Josi]

I can tell you from experience bells do not work well. Cats are pretty stealthy. They move very slow without the bell making a sound, and then pounce.

 

[treesparrow]

I can tell you from experience bells do not work well. Cats are pretty stealthy. They move very slow without the bell making a sound, and then pounce.

Yes, it does look that way according to this article -

Change your cat's bell to save birds


The age-old technique of attaching a bell to a cat's collar to warn birds of its approach is losing its effectiveness because cats are learning to walk without ringing them.

_http://www.telegraph.co.uk/lifestyle/pets/7782632/Change-your-cats-bell-to-save-birds.html


It goes on suggest brightly coloured collars as a possible alternative solution which apparently are more successful according to this research -

"Reducing the rate of predation on wildlife by pet cats: The efficacy and practicability of collar-mounted pounce protectors" BIOLOGICAL CONSERVATION, Vol 137, Issue 3, July 2007, pp 341-348

Michael Calvera, Sandra Thomasa, Stuart Bradleya, and Helen Murdoch UniversityMcCutcheonb a-School of Biological Sciences and Biotechnology, Murdoch University, Murdoch, Western Australia, Australia b-School of Veterinary Studies, Murdoch University, Murdoch, Western Australia, Australia

SUMMARY

In an attempt to provide sound advice to owners seeking to curb the predatory behaviour of their pet cats, we evaluated whether or not the commercial collar-worn product the CatBib reduces the number of vertebrates caught by pet cats. We also tested whether the colour of the CatBib influenced its effectiveness, or if supplementing the CatBib with a bell could reduce predation further. Fifty-six cats identified by their owners as known hunters completed the study, which took place in Perth, Western Australia over a six-week period in November/December 2005 (southern hemisphere late spring/early summer). Each cat spent a period of three weeks wearing a CatBib and three weeks without it and the number of prey brought home during each period was recorded. Participating cats caught a total of 13 bird species, five mammal species, and 11 herp (reptile and frog) species. The mammal the Southern Brown Bandicoot was the only prey species of conservation concern. CatBibs stopped 81% of
cats from catching birds, 45% of cats from catching mammals, and 33% of cats from catching herptofauna. CatBibs of both colours were equally effective at reducing predation. There was no statistically significant evidence that adding bells conferred additional protection. Most cats (86%) adjusted almost immediately to wearing a CatBib, 10% took a day or so and only 4% took longer.

edit forgot link-
_http://www.catgoods.com/field-trial-results.php

 

[mcb]

...Btw I think I'm may becoming emotionally invested in this discussion, maybe not a good thing :) Chance for self observation maybe?

Maybe, or maybe I am confused. To me a "domestic cat" is a species. Some are owned, some are abandoned, and some are feral. Whenever I have heard about this problem, it has been the unowned ones that were causing ecological trouble, and putting bells on them would mean they would have to either go cause some other kind of trouble or starve. But I could be wrong.

I know that here in Sacramento some cats live in the American River Parkway preserve, because I saw them when I used to go walking there regularly. I also saw coyotes, and our vet has described runaway housecats as "coyote food." If there were other larger predators then I wouldn't think that unowned cats would be such a problem. It's when the humans kill off all the larger predators for "convenience" (or introduce smaller ones where there were none before) that the big problems emerge.

 

[treesparrow]

...Btw I think I'm may becoming emotionally invested in this discussion, maybe not a good thing :) Chance for self observation maybe?

Maybe, or maybe I am confused. To me a "domestic cat" is a species. Some are owned, some are abandoned, and some are feral. Whenever I have heard about this problem, it has been the unowned ones that were causing ecological trouble, and putting bells on them would mean they would have to either go cause some other kind of trouble or starve. But I could be wrong.

I know that here in Sacramento some cats live in the American River Parkway preserve, because I saw them when I used to go walking there regularly. I also saw coyotes, and our vet has described runaway housecats as "coyote food." If there were other larger predators then I wouldn't think that unowned cats would be such a problem. It's when the humans kill off all the larger predators for "convenience" (or introduce smaller ones where there were none before) that the big problems emerge.

OK, I think I see where we each may be confused and maybe talking at cross purposes.

By domestic cats I meant well looked after owned ones and not individuals once domesticated but now gone feral for whatever reason. I agree it is feral ones causing the bulk of the killing and I again I'm not suggesting belling those or any taking any other measures, which might hamper their abilities to kill and feed themselves. I don't know what can be done about this problem, that is, if it is a problem. Is the level of cat predation really having a long term effect on bird population levels ? (that maybe is the most important question). Would those creatures killed by cat succumbed to some other predator anyway - had the cats been absent - partly because they were young, sick or inexperienced? Who knows?

 

[Gimpy]

By domestic cats I meant well looked after owned ones and not individuals once domesticated but now gone feral for whatever reason. I agree it is feral ones causing the bulk of the killing and I again I'm not suggesting belling those or any taking any other measures, which might hamper their abilities to kill and feed themselves. I don't know what can be done about this problem, that is, if it is a problem. Is the level of cat predation really having a long term effect on bird population levels ? (that maybe is the most important question). Would those creatures killed by cat succumbed to some other predator anyway - had the cats been absent - partly because they were young, sick or inexperienced? Who knows?

Domesticated cats are one of the few species that will kill another animal just for the exercise, and not for food. That is why they are so devastating when the population goes too high in the wild. In our area, stray cats, and barn cats are killed by cars and coyotes more than they die from starvation.

Where I live in the country, the local song bird population dips as the stray cat population rises. Its evened out by coyote packs, which prey on strays of all species.

Having seen how cats can destroy an ecosystem, I'm not averse to culling any population of stray cats when an endangered ecosystem is being stressed by them.