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How Much of an Impact Do Cats Make on Wildlife?
It is an undeniable fact that cats are carnivores; their physiology demands this. However, the debate on cat predation focuses on the impact on the other species in their ecosystem. While it is clear that cats can and do have a large impact in exceptional situations (isolated ecosystems being the primary example), it is much more apparent that in our normal, everyday environments the actions of humans have a much greater effect on vulnerable and threatened species. Urban sprawl, fragmentation of forested ecosystems, the increase in motor vehicles and the related increase in roads, and the use of pesticides, fertilizers and poisons do much more damage to bird and small vertebrate species than do domestic and/or feral cats. However, feral cat predation, and its’ supposed effect on vulnerable species, is frequently used as an argument against trap/neuter/return (TNR) programs. As cats are opportunistic feeders, providing them with a readily available food source as a part of a TNR program will reduce any effect they have on their traditional prey species. All cats, and feral cats in particular, have become convenient scapegoats for the loss of many species, especially songbirds. However, we can no longer ignore the role that we humans have played in this process. Before we can sentence cats to death for being carnivores, we need to take a hard look at ourselves and what we have done to our ecosystem.
~excerpt from Feral Cat Predation and It’s Effect on Wildlife - Searching for the Truth
Articles and Links
Feral Cat Predation and It’s Effect on Wildlife - Searching for the Truth Article by Christine L. O’Keefe, PhD which reviews various cat predation studies from a scientific point of view. Also available in PDF Format for printing. If you have trouble with the link to the PDF version of the article, please copy and paste this web address into your browser: http://www.straypetadvocacy.org/PDF/FeralCatPredation.pdf
Addressing “The Wisconsin Study” Article by Stray Pet Advocacy which addresses the study which is cited most often by wildlife conservationists to show the decimating effect that free-ranging cats have on bird populations. The conclusion of the article is that this study simply does not stand up to scientific scrutiny. PDF version available for printing. If you have trouble with the link to the PDF version of the article, please copy and paste this web address into your browser: http://www.straypetadvocacy.org/PDF/TheWisconsinStudy.pdf 11/3
”Domestic Cats - Wildlife Enemy Number One or Convenient Scapegoats?” Article by Sarah Hartwell ©2001. Cat predation studies with commentary as to where the research flaws may exist. If you have trouble with this link, please copy and paste this web address into your browser: http://www.messybeast.com/cat-wildlife.htm
”The Alternative Cat Predation Survey” by Sarah Hartwell ©2002. Hosted by Moggy Cat’s Cat Pages, this article takes a humorous look at how easily statistics can be manipulated. If you have trouble with this link, please copy and paste this web address into your browser: http://members.aol.com/moggycat/affy_16.html
“Myths and Facts about Feral Cats” © 2000-2003 Metro Animal Resource Services, Inc. Included in this easy-to-use chart are several audio presentations about cat predation. (Scroll down ~3/4 down the page for the table of Myths and Facts.) If you have trouble with this link, please copy and paste this web address into your browser: http://www.metroanimal.org/feral/main.html#myths_facts
What Kills Birds? Curry & Kerlinger, LLC. Curry & Kerlinger, LLC (consultants to the Wind Power industry on birds and other wildlife issues) have compiled data that indicate the following statistics regarding annual bird deaths.
Glass Windows. Bird Deaths a year: 100 to 900+ million - Dr. Daniel Klem of MuhlenbergCollege has done studies over a period of 20 years, looking at bird collisions with windows. His conclusion: glass kills more birds than any other human related factor.
Hunting. Bird Deaths a year: 100 + million - According to the U.S. Fish and Wildife Service, more than 100 million ducks, geese, swans, doves, shorebirds, rails, cranes, among others are harvested legally each year.
House Cats: 100 million - (though we take issue with the studies that provide this conclusion. Please see our article “Feral Cat Predation Examined,” by Christine O’Keefe, PhD, above).
Automobiles & Trucks. Bird Deaths a year: 50 to 100 Million - Scientists estimate the number of birds killed by cars and trucks on the nation's highways to be 50 to 100 million a year. Those statistics were cited in reports published by the National Institute for Urban Wildlife and U.S. Fish and Wildlife Service.
Electric Transmission Lines. Bird Deaths a year:up to 174 million - Estimates made by the U.S. Fish and Wildife Service demonstrate millions of birds die each year as a result of colliding with transmission lines.
Agriculture (Pesticides). Bird Deaths a year: 67 million - Pesticides likely poison an estimated 67 million birds per year according to the Smithsonian Institution. Cutting hay may kill up to a million more birds a year.
CommunicationTowers. Bird Deaths a year: 4 to 10 million - U.S. Fish and Wildlife Service estimates that bird collisions with tall, lighted communications towers, and their guy wires result in 4 to 10 million bird deaths a year.
Oil and Gas Extraction. Bird Deaths a year: 1 to 2 million - The U.S. Fish and Wildlife Service reports that up to 2 million birds died landing in oil pits to bathe and drink in 1997. Fish and Wildlife says netting has improved that situation somewhat. There are no overall estimates for the number of birds affected by oil and gas spills, and oil and gas extractions (and transport.)
If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.currykerlinger.com/birds.htm
About Pesticides and Birds. ©American Bird Conservancy. “Some pesticides can, and do, kill birds - songbirds, gamebirds, raptors, sea and shorebirds, among others. 672 million birds are directly exposed each year by pesticides on farms alone - according to one conservative estimate - and 10% of these, or roughly 67 million birds, die. According to the US Fish & Wildlife Service, approximately 50 pesticides currently used in the US have caused bird die-offs.” Hosted by www.abcbirds.org. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.abcbirds.org/pesticides/
Communications Towers are Bird Killers. ©2000 “Banks (1979) estimated that 1.2 million birds per year were killed by communications towers across the USA. He based this figure on data from three towerkill studies suggesting an annual mortality at tall TV towers of 2500 birds per tower. The FCC had informed him that there were 1010 television transmitting stations in the USA as of February 1975 and he figured that, if half of these stations had a mortality like the studies suggested, 1.2 million birds would be killed annually.” For more information, please visit www.towerkill.com. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.towerkill.com/issues/consum.html
Glass: Silent but Deadly. ©Fall 1995, Touching Down, a newsletter of www.flap.org (Fatal Light Awareness Program). “If you believe that windows in general pose a serious threat to birds, you're perfectly right. Daniel Klem Jr., a biologist at MuhlenbergCollege in Pennsylvania, conservatively estimates that every year over 100 million birds die as a result of hitting glass in the United States alone.” The above article can be found in FLAP’s ‘Who We Are’ section. Just click on Newsletters in FLAP Archives. FLAP’s site is not designed so that we can provide direct links to articles and information on the site.
“How Do Free Roaming cats Impact Humans and Wild Animals?” A JAVMA review (in PDF format) considers whether TTVAR Programs are Feasible and Human by Dr. Gary Patronek of TuftsUniversity. Summary published in Animal Sheltering Magazine, May – June 1998. “Many people believe free-roaming and feral cats hunt and kill an enormous number of songbirds and other wild animals, but few studies indicate any long term effects, and many provide evidence to the contrary.” If you have trouble with the above link, please copy and paste this web address directly you’re your browser: http://www.hsus2.org/sheltering/magazine/currentissue/may_jun98/free_roaming.pdf 10/31
“Cats – Love them or Hate them!” ©2003 Songbird Survival (UK) “Cats are frequently singled out as the primary reason for the disappearance of Britain's songbirds. But is this label really justified? SongBird Survival thinks not!… If we compare the predation rates of cats and sparrowhawks on birds alone, this highlights some very interesting facts. For example, Britain's population of 10 million cats is said by the CPL to be responsible for killing 55 million songbirds each year - an average of 5.5 per cat. Yet by comparison, and calculating from the predation rate quoted by Dr Ian Newton in his book The Sparrowhawk, the UK's estimated population of 100,000 sparrowhawks will slaughter in excess of 100 million songbirds during the same period - an average of 1,000 'kills' per sparrowhawk. This strongly indicates that sparrowhawks are responsible for killing almost DOUBLE the total number of songbirds predated by cats. And on a 'one-to-one' basis, each sparrowhawk kills the same number of songbirds as the total taken by 180 cats!” If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.songbird-survival.org.uk/cats.htm 10/31
Julie Levy’s, (DVM, PhD, DACVIM) report to the Florida Fish and Wildlife Conservation Commission in Kissimmee, Florida on May 30, 2003. (PDF) Dr. Levy address the fact that Florida’s Feral Cat Issue Team overlooked a number of well-constructed studies that have been reported in peer-reviewed scientific literature. Her address to the Commission goes on to cite the many studies addressing TNR programs and their success, transmission of disease issues and cat predation. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.alleycat.org/pdf/levycomments.pdf 10/31
“The Truth about Cats and Wildlife,” ©2003, Eva Berriman, as hosted on her site, Animal Welfare: Human Dependent Animals. “Rightly or wrongly, environmental groups and councils have increasingly called for the confinement of cats to prevent their predation on birds and other wildlife. Cats do impact on wildlife, like humans they kill to eat, but there has been a great deal of misinformation and propaganda about the true harm they do. This debate has become so heated at times, fueled by a minority of vocal cat haters who often have the ear of government, that people have lost sight of the fact that it is humans themselves who are the real culprits. Massive, ongoing and largely irreversible damage to the environment by human activity is the main reason for the loss of wildlife, the impact of cats being infinitesimal in comparison. In fact if given a choice, cats mainly prey on pest species such as rodents and rabbits as they have done for millennia, with the full endorsement of humans.” If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.users.bigpond.com/berrime/wildcats.htm 10/31
“Exotica,” 1999. Jeff Elliot. Posted October 19, 1999 4:34 UTC. Deep Ecology Forum of the Communications for a Sustainable Future (CSF). Significant support for CSF has come from the Corporation for National Service, the International Studies Association, and the Communications Initiative of the University of Colorado. Excerpt: “I wrote two 1994 articles on feral cats, and was shocked by the ignorance of "experts" from the Audubon Society and government officials who were vocal about the evils of ferals. There is very good data about what feral cats eat -- all the science shows that birds are only about five percent of their diet. (Mostly they eat rodents and other small mammals, populations which did not diminish as human habitation forced out foxes and other predators.) "Five percent? Really? That's surprisingly low," one respected ornithologist told me. Despite his outspoken opinions about feral cat colonies, he had never actually read the cat-science. And even more surprisingly, this doesn't seem unusual. The bird-people have only the foggiest ideas about the science literature on cats…. I also found that ferals are an easy scapegoat for the more complex issue of human encroachment.” Jeff Elliot is editor of the Albion Monitor (http://www.monitor.net/monitor) If you have trouble with the above link, please copy and paste this web address directly into your browser: http://csf.colorado.edu/forums/deep-ecology/jun99/msg00720.html 10/31
“Understanding Cats and Predation,” ©2000, Alley Cat Allies. Reprinted with permission and hosted by the Stanford Cat Network. “While many studies have shown that cats do not have a detrimental impact on wildlife on continents, there are several who feel that cats are to blame for the depletion of songbirds and other animals. Two studies most often quoted are the StanleyTemple study and the Churcher /Lawton study. Some groups use these studies in misguided effort s to discredit our work to humanely control feral cats. Over sixty studies have been done on different continents all showing three very important points:
Cats are opportunistic feeders, eating what is most easily available. Feral cats are scavengers, and many rely on garbage and hand-outs from people.
Cats are rodent specialists. Birds make up a only small percentage of their diet when they rely solely on hunting for food.
Cats may prey on a population without destroying it. If this weren't so, we would no longer have any mice around.
Even though some cats can become efficient hunters and do kill birds, many international biologists agree that only on small islands do cats possibly pose a severe threat to the wildlife populations. They agree with biologist C.J. Mead that ‘Any bird populations on the continents that could not withstand these levels of predation from cats and other predators would have disappeared long ago...’ "
If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.stanford.edu/group/CATNET/articles/understd_pred.html 10/31
“Feral Cats on the Firing Line,” ©San Francisco SPCA. “For all the talk of cat predation, science exonerates our friends…. A 1994 World Watch Institute Study showed, for example, that of the world’s 9,000 bird species, 5,000 are in decline, while another 1,600 are threatened or nearly threatened with extinction. Some populations have fallen by 75% as a result of four primary factors: habitat loss, overtrapping, drought and pesticides. Cats are notably absent as factors.” If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.sfspca.org/gifs/pdf_feralcats/firing.pdf 10/31
Help Us End The Anti-Cat Campaign. ©2000 Alley Cat Allies: reprinted with permission and hosted by Austin Feral Cats. “The English Churcher/Lawton study is often quoted as well. This small study also extrapolated the data across Britain and stated that cats were killing 100 million birds and small mammals each year….Roger Tabor, British biologist, says of this study: “It is not realistic to multiply the numbers of catches of these (70) rural cats by the entire cat population of Britain. Most cats are town cats with small ranges, and catch fewer items of prey than the village cats of this survey. The mesmeric effect of big numbers seems to have stultified reason.” If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.austinferalcats.org/birds.htm 10/31
Migratory Bird Mortality, US Fish & Wildlife "The greatest threat to birds and all wildlife continues to be loss and/or degradation of habitat due to human development and disturbance." US Fish & Wildlife conclude that: “Declining bird populations are probably most often the result of combined or cumulative impacts of all mortality, thus addressing each of the contributing factors is a priority. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://birds.fws.gov/mortality-fact-sheet.pdf 12/10
“Cats - Myths, Facts and Other Considerations” Australia is a definite hot spot where the debate on feral cats is heated. This article, by Frankie Seymore, dispels many of the common myths about the impact that feral cats have on Australia’s unique ecosystem. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.animalsaustralia.org/default2.asp?IDL1=1274&IDL2=1310 12/10
Wildlife Predation & TNR – Taking a Common Sense Approach. Essay by Neighborhood Cats. While the debate rages about the impact that feral cats have on wildlife, the solution is the same no matter the conclusion. TNR is still the only way to manage feral cats the potential predation impact on wildlife. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.neighborhoodcats.org/about/about_essays_old_4.htm 2/27/04
Feral Cats and Native Birds A look at cat predation from the bird advocate’s point of view. Gloria Scholbe tries to find a reasonable compromise for the birds and the cats. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.holisticbirds.com/hbn03/spring03/pages/feralcats.htm 2/27/04
Glass windows an 'indiscriminate' bird killer Article from CNN dated February 3, 2004 states that glass buildings could be the second leading cause of bird deaths, second only to habitat destruction. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.cnn.com/2004/TECH/science/02/03/birds.clear.danger.ap/index.html 2/27/04
Backyard Birds and Predators from The Whole Cat Journal by Angela Kessler discusses ways to protect birds from roaming cats, as well as ways to keeping owned cats safer in a confined area, such as the backyard of the owner. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.wholecatjournal.com/articles/predators.htm 2/27/04
The Feline Resistance “The existing network of feline protectors has been overwhelmed by government agencies influenced by an insidious propaganda campaign. The principals of The Feline Resistance! believe that in addition to education, it is now necessary to empower local cat advocates with the capability to expose the lies and stop the killing . . .” The Feline Resistance presents information that contests ABC Birds Cats Indoors! program information. If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.felineresistance.org 5/15/04
**NEW** Defenders of Wildlife, “Plight of the Songbird” “…Birds, of course, are dying from many other causes, including natural ones. The fact is, more than half the population of most bird species die every year. At least 100 million birds die every year from crashing into windows, scientists estimate. But windows, cats, West Nile virus, wind turbines — all those specific causes of death that are apparent in people's backyards -- are not, at present, having any known effect on the population size of any continental bird species, Rappole says. Numbers of individual birds killed simply do not constitute evidence of an overall population decline.” If you have trouble with the above link, please copy and paste this web address directly into your browser: http://www.defenders.org/defendersmag/issues/spring03/plightsongbird.html 04/16/06
Posted on SHARE Yahoo group - May 11, 2006