Cat predation on wildlife
Cat predation on wildlife is the result of the natural instincts and behavior of both feral and domesticated cats to hunt small prey, including wildlife. Some people view this as a desirable phenomenon, such as in the case of barn cats and other cats kept for the intended purpose of pest control; however, contrary to popular belief, there is no scientific evidence that cats are an effective means of rodent control, and ecologists oppose their use for this purpose because of the disproportionate harm they do to beneficial native wildlife. As an invasive species and superpredator, they do considerable ecological damage. In Australia, hunting by cats helped to drive at least 20 native mammals to extinction, and continues to threaten at least 124 more. Their introduction has caused the extinction of at least 33 endemic species on islands throughout the world. Feral and domestic cats kill billions of birds in the United States every year, where songbird populations continue to decline.
A 2013 study by Scott R. Loss and others of the Smithsonian Conservation Biology Institute and the U.S. Fish and Wildlife Service found that free-ranging domestic cats (mostly unowned) are the top human-caused threat to wildlife in the United States, killing an estimated 1.3 to 3.7 billion birds and 6.3 to 22.3 billion mammals annually. These figures were much higher than previous estimates for the U.S.:2 Unspecified species of birds native to the U.S. and mammals including mice, shrews, voles, squirrels and rabbits were considered most likely to be preyed upon by cats.:4
Perhaps the first U.S. study that pointed to predation by cats on wildlife as a concern was ornithologist Edward Howe Forbush's 1916 report for the Massachusetts State Board of Agriculture, The Domestic Cat: Bird Killer, Mouser and Destroyer of Wildlife: Means of Utilizing and Controlling It.
Island settings pose particular challenges for wildlife. A 2001 study identified cats alone as responsible for the plight of some island bird species, such as the Townsend's shearwater, socorro dove, and the Marquesan ground dove.:400 The same study identified the greatest cause of endangerment of birds as habitat loss and degradation, with at least 52% of endangered birds affected,:399 while introduced species on islands, such as domestic cats, rats and mustelids,:403 affected only 6% of endangered birds.:399 Other studies caution that removing domestic cats from islands can have unintended consequences, as increasing rat populations can put native bird and mammal species at risk.
Impact by location
Cats in Australia have been found to have European origins. This is important to note because of their effect on native species. Feral cats in Australia have been linked to the decline and extinction of various native animals. They have been shown to cause a significant impact on ground nesting birds and small native mammals.
Feral cats have also hampered any attempts to re-introduce threatened species back into areas where they have become extinct as the cats have hunted and killed the newly released animals. Numerous Australian environmentalists claim the feral cat has been an ecological disaster in Australia, inhabiting most ecosystems except dense rainforest, and being implicated in the extinction of several marsupial and placental mammal species. Some inhabitants have begun eating cat meat to mitigate the harm that wild cats do to the local wildlife.
In 2020, it was reported that a culling of feral cats that had recently begun in Dryandra Woodland, in Western Australia, had caused the population of numbats to triple in number, the largest number of the endangered marsupial to have been recorded there since the 1990s.
Domestic cats are common throughout China, and the number of pet cats in the country increased at a rate of 8.6% from 2018 to 2019. A 2021 estimate based on a public survey estimated that outdoor cats kill "1.61–4.95 billion invertebrates, 1.61–3.58 billion fishes, 1.13–3.82 billion amphibians, 1.48–4.31 billion reptiles, 2.69–5.52 billion birds, and 3.61–9.80 billion mammals" there each year. The authors recommended policies be implemented, such as a public education initiative to encourage people to keep their cats indoors, and building more animal shelters. They also recommended that TNR programs "should be limited until rigorous, peer-reviewed studies are able to show that such efforts consistently attain the sterilization rates needed to result in stabilization and permanent decline of unowned cat populations," as they said that most TNR programs fail to do this.
The fauna of New Zealand has evolved in isolation for millions of years without the presence of mammals (apart from a few bat species). Consequently, birds dominated the niches occupied by mammals and many became flightless. The introduction of mammals after settlement by Māori from about the 12th century had a huge effect on indigenous biodiversity. European explorers and settlers brought cats on their ships and the presence of feral cats was recorded from the latter decades of the 19th century. It is estimated that feral cats have been responsible for the extinction of six endemic bird species and over 70 localised subspecies as well as depleting bird and lizard species.
This section contains too many or overly lengthy quotations for an encyclopedic entry. (July 2020)
In the UK, the Royal Society for the Protection of Birds says there is no scientific evidence that predation by cats is having any effect on the population of birds UK-wide. They say that starvation and disease, and predation by other animals, are greater drivers of bird mortality, and that cats preferentially kill "weak or sickly" birds. They also say that the bird species that are showing the most serious population declines don't commonly encounter cats. They attribute the decline in bird populations to habitat loss.
Nick Forde, a trustee of the UK charity SongBird Survival, said the RSPB's claim of no evidence was disingenuous because adequate studies had not been done, in part due to the RSPB's position. Forde accused the RSPB of downplaying the effect of cat predation on birds in the UK to avoid offending "old ladies who might own cats", who he said are some of the RSPB's most generous benefactors. The RSPB's head of nature policy, Jeff Knott, denied that the agency was downplaying the effects of predation by cats. Knott said that cat predation was not a conservation issue, and that the RSPB was not afraid of potentially offending its members. He added that the Royal Society for the Protection of Birds had no plans to spend funds studying the effects of cat predation on birds.
In the UK, it is common to allow pet cats access to the outdoors. SongBird Survival considers that "the prevailing line that 'there is no scientific evidence that predation by cats is having any impact on bird populations in UK' is simply no longer tenable", and that "no study has ever examined the impact of cats on songbirds at the population level; evidence shows that the recovering sparrowhawk population in the 1970-80s resulted in the decline of some songbird populations; cats kill around 3 times as many songbirds as sparrowhawks; the mere presence of cats near birds' nests was found to decrease provision of food by a third while the resultant mobbing clamour from parent birds led in turn to increased nest predation by crows and magpies; [and that] it is therefore far more likely that cats have an even greater impact on songbird populations than sparrowhawks".
Sir David Attenborough in his Christmas Day, 2013, edition of BBC Radio 4 programme Tweet Of The Day said "cats kill an extraordinarily high number of birds in British gardens". Asked whether cat owners should buy bell collars for their pets at Christmas, he replied: "that would be good for the robins, yes".
Consequences of introduction
Many islands host ecologically naive animal species. That is, animals that do not have predator responses for dealing with predators such as cats. Feral cats introduced to such islands have had a devastating impact on these islands' biodiversity.
They have been implicated in the extinction of several species and local extinctions, such as the hutias from the Caribbean, the Guadalupe storm petrel from the Pacific coast of Mexico, and Lyall's wren. In a statistical study, they were a significant cause for the extinction of 40% of the species studied. Moors and Atkinson wrote, in 1984, "no other alien predator has had such a universally damaging effect."
Feral cats, along with rabbits, some sea birds, and sheep, form the entire large animal population of the remote Kerguelen Islands in the southern Indian Ocean. Although exotic mammals form the bulk of their diet, cats' impact on seabirds is very important.
Because of the damage cats cause in islands and some ecosystems, many conservationists working in the field of island restoration have worked to remove feral cats. (Island restoration involves the removal of introduced species and reintroducing native species.) As of 2004[update], 48 islands have had their feral cat populations eradicated, including New Zealand's network of offshore island bird reserves and Australia's Macquarie Island.
Larger projects have also been undertaken, including their complete removal from Ascension Island. The cats, introduced in the 19th century, caused a collapse in populations of nesting seabirds. The project to remove them from the island began in 2002, and the island was cleared of cats by 2004. Since then, seven species of seabird that had not nested on the island for 100 years have returned.
In some cases, the removal of cats had unintended consequences. An example is Macquarie Island, where the removal of cats caused an explosion in the number of rabbits, that started feeding of the island's vegetation, thus leaving the birds without protection to other predators, like rats and other birds even if the eradication was positioned within an integrated pest management framework. The removal of the rats and rabbits was scheduled for 2007 and it could take up to seven years and cost $24 million.
Mice and rats
Cats are sometimes intentionally released into urban environments on the popular assumption that they will control the rat population; but there is little scientific basis for this. The reality is that cats find rats to be large and formidable prey, and so they preferentially hunt defenseless wildlife such as lizards and songbirds instead. Scientists and conservationists oppose the use of cats as a form of rodent control because they are so inefficient at destroying pest species that the harm they do to native species in the process outweighs any benefit.
Cat attack outcomes
Wildlife that are attacked by cats fare poorly, even when provided with veterinary treatment by licensed wildlife rehabilitators (over 70% of mammals and over 80% of birds died in spite of treatment in one study).:p. 171 Even those that had no visible injuries from the cat attack often died (55.8% of birds, 33.9% of mammals).:p. 169 Typical wildlife injuries caused by cats include cuts, degloving (the stripping off of skin), and small puncture wounds caused by prey being gripped by the cat's teeth that are easily hidden by fur or feathers.:p. 171 Systemic infection, usually caused by Pasteurella multocida, a highly pathogenic bacterial species that's found naturally in cat mouths, can kill small animals in as little as 15 hours.:p. 171 Few other causes of injury that are commonly seen by wildlife care facilities lead to death as rapidly:p. 171 or as frequently as interaction with a cat.:p. 170
Cat owner attitudes
Predation by pet cats is an environmental issue that cannot be resolved until cat owners accept that the problem exists and individually take responsibility for addressing it. Surveys of cat owners find they often view the depredation of wildlife as a normal thing that cats do, and rarely feel an individual obligation to prevent it. They may experience some level of cognitive dissonance toward the subject, because when surveyed they're more likely than the general public to believe that cat predation isn't harmful to wildlife, despite the likelihood they have witnessed acts of predation firsthand, and in many cases have been receiving "gifts" of animal carcasses from their cats. Those that express concern also often express a belief that, despite owning the animal, they have no control over what it does, or believe that they can't manage its behavior without compromising the cat's welfare in some way. A few cat owners even take pride in the animals their cats return home, believing it represents the cat's authenticity or skill.
- Surplus killing, biology
- Price Persson, Charlotte (26 November 2017). "Scientist: Australia's feral cats should be eradicated". ScienceNordic.
- Nogales, Manuel; Vidal, Eric; et al. (1 October 2013). "Feral Cats and Biodiversity Conservation: The Urgent Prioritization of Island Management" (PDF). BioScience. 63 (10): 804–810. doi:10.1525/bio.2013.63.10.7.
- "Tackling Feral Cats and Their Impacts - Frequently asked questions" (PDF). Australian Government Department of the Environment and Energy. Retrieved 12 May 2018. CS1 maint: discouraged parameter (link)
- Loss, Scott R.; Will, Tom; Marra, Peter P. (2013). "The impact of free-ranging domestic cats on wildlife of the United States". Nature Communications. 4: 1396. doi:10.1038/ncomms2380. PMID 23360987. Archived from the original on 2014-09-04.
- Morelle, Rebecca (29 January 2013). "Cats killing billions of animals in the US". BBC News. Retrieved 12 February 2013. CS1 maint: discouraged parameter (link)
- Edward Howe Forbush, "The Domestic Cat: Bird Killer, Mouser and Destroyer of Wildlife: Means of Utilizing and Controlling It", Commonwealth of Massachusetts, State Board of Agriculture, Economic Biology Bulletin 42, 1916.
- Collar, N. J. (2001). Endangered Birds (PDF). 2. New York: Academic Press. p. 400. in Encyclopedia of Biodiversity
- Fan, M; Kuang, Y; Feng, Z (September 2005). "Cats protecting birds revisited". Bull Math Biol. 67 (5): 1081–106. CiteSeerX 10.1.1.152.4561. doi:10.1016/j.bulm.2004.12.002. PMID 15998496.
- Hanna, Emily; et al. (April 2014). "Island mammal extinctions are determined by interactive effects of life history, island biogeography and mesopredator suppression". Global Ecology and Biogeography. 23 (4): 395–404. doi:10.1111/geb.12103.
- Popkin, Gerald (29 August 2013). "Feral cats help some endangered mammals survive, report says". The Sydney Morning Herald.
- Spencer, Peter B.S.; Yurchenko, Andrey A.; David, Victor A.; Scott, Rachael; Koepfli, Klaus-Peter; Driscoll, Carlos; O’Brien, Stephen J.; Menotti-Raymond, Marilyn (9 November 2015). "The Population Origins and Expansion of Feral Cats in Australia". Journal of Heredity. 107 (2): 104–114. doi:10.1093/jhered/esv095. PMC 4757960. PMID 26647063.
- Dickman, Chris (May 1996). Overview of the Impacts of Feral Cats on Australian Native Fauna (PDF). The Director of National Parks and Wildlife – Australian Nature Conservation Agency – Institute of Wildlife Research. ISBN 978-0-642-21379-2. Archived from the original (PDF) on 4 March 2016. Retrieved 11 February 2013. CS1 maint: discouraged parameter (link)
- The Threat Of Feral Cats. Environment.nsw.gov.au (28 October 2011). Retrieved on 5 May 2013.
- Robley, A.; Reddiex, B.; Arthur, T.; Pech, R.; Forsyth, D. (Sep 2004). "Interactions between feral cats, foxes, native carnivores, and rabbits in Australia" (PDF). CSIRO Sustainable Ecosystems / Arthur Rylah Institute for Environmental Research. Archived from the original (PDF) on 17 March 2011. Retrieved 12 February 2013. CS1 maint: discouraged parameter (link)
- Mercer, Phil (2007-09-02). "Australians cook up wild cat stew". BBC News.
- Dobson, Johnson; Hussey, Toby. "Numbat numbers at WA's Dryandra Woodland grow as feral cat culling program kicks in". ABC. Retrieved 20 November 2020. CS1 maint: discouraged parameter (link)
- Li, Yuhan; Wan, Yue; Shen, Hua; Loss, Scott R.; Marra, Peter P.; Li, Zhongqiu (January 2021). "Estimates of wildlife killed by free-ranging cats in China". Biological Conservation. 253. doi:10.1016/j.biocon.2020.108929. Retrieved 14 February 2021.
- King, Carolyn (1984) Immigrant Killers. Auckland: Oxford University Press. ISBN 0-19-558121-0
- Eason, Charles T.; Morgan, David R. & Clapperton, B. Kay (1992). Toxic bait and baiting strategies for feral cats. University of Nebraska – Lincoln: Proceedings of the Fifteenth Vertebrate Pest Conference 1992.
- "Are cats causing bird declines?" The Royal Society for the Protection of Birds, accessed 23 June 2014.
- Webster, Ben (30 December 2015). "RSPB accused of going soft on cats to appease donors". The Sunday Times. Retrieved 27 September 2020. CS1 maint: discouraged parameter (link)
- "In the UK, the vast majority of pet cats have free access to the outside world, or are at least allowed to go outside unsupervised for large parts of the day." "A world of difference – How cat ownership in America differs to the UK", Pets4Homes, accessed 1 September 2014.
- "Archived copy". Archived from the original on 2016-07-31. Retrieved 2017-03-22.CS1 maint: archived copy as title (link)
- "Cats killing huge numbers of British birds, Sir David Attenborough warns". The Guardian. 10 December 2013.
- Moors, P.J.; Atkinson, I.A.E. (1984). "Predation on seabirds by introduced animals, and factors affecting its severity" in Status and Conservation of the World's Seabirds. Cambridge: ICBP. ISBN 0-946888-03-5.
- Barcott, Bruce (2 December 2007). "Kill the Cat That Kills the Bird?". The New York Times.
- Pontier, D.; E. Natoli; L. Say; F. Debias; J. Bried; J. Thioulouse; T. Micol & E. Natoli (2002). "The diet of feral cats (Felis catus L.) at five sites on the Grande Terre, Kerguelen archipelago" (PDF). Polar Biology. 25 (11): 833–837. doi:10.1007/s00300-002-0424-5.
- Nogales, Manuel; Martin, Aurelio; Tershy, Bernie R.; Donlan, C. Josh; Veitch, Dick; Puerta, Nestor; Wood, Bill; Alonso, Jesus (2004). "A review of feral cat eradication on islands" (PDF). Conservation Biology. 18 (2): 310–319. doi:10.1111/j.1523-1739.2004.00442.x. hdl:10261/22249.
- Cat eradication from Ascension Island. Petsaspests.blogspot.com (2014-01-23). Retrieved on 2015-11-01.
- "Up against rats, rabbits and costs". The Sydney Morning Herald. 12 April 2007.
- Fears for sub-antarctic island plagued by rabbits. ABC News (15 July 2006).
- Draper, Michelle and La Canna, Xavier (14 January 2009) Cat kill devastates Macquarie Island. Nine News
- Controversy on feral cat removal on Macquarie Island. Petsaspests.blogspot.com.es (2013-05-14). Retrieved on 2015-11-01.
- Macquarie Island World Heritage Area. Plan for the Eradication of Rabbits and Rodents on Macquarie Island. Parks and Wildlife Service, Tasmania. parks.tas.gov.au
- Kobilinsky, Dana. "Rats! Feral cats fail at urban rodent control". The Wildlife Society. Retrieved 28 February 2020. CS1 maint: discouraged parameter (link)
- Parsons, Michael H.; Banks, Peter B.; Deutsch, Michael A.; Munshi-South, Jason (27 September 2018). "Temporal and Space-Use Changes by Rats in Response to Predation by Feral Cats in an Urban Ecosystem". Frontiers in Ecology and Evolution. doi:10.3389/fevo.2018.00146. Retrieved 28 February 2020. CS1 maint: discouraged parameter (link)
- Solly, Meilan. "Cats Are Surprisingly Bad at Killing Rats". SMITHSONIANMAG.COM. Smithsonian Magazine. Retrieved 28 February 2020. CS1 maint: discouraged parameter (link)
- "North Side’s 47th Ward Using Feral Cats To Catch Rats", CBS Chicago, 28 June 2012.
- Mcruer, Dave L.; Gray, Lincoln C.; Horne, Leigh-Ann; Clark Jr., Edward E. (21 June 2016). "Free-roaming Cat Interactions With Wildlife Admitted to a Wildlife Hospital". Journal of Wildlife Management. doi:10.1002/jwmg.21181.
- Crowley, Sarah L.; Cecchetti, Martina; McDonald, Robbie A. (30 July 2018). "Hunting behaviour in domestic cats: An exploratory study of risk and responsibility among cat owners". People and Nature. doi:10.1002/pan3.6. Retrieved 2 March 2021.
- Loyd, Kerrie Ann T.; Hernandez, Sonia M. (28 April 2015). "Public Perceptions of Domestic Cats and Preferences for Feral Cat Management in the Southeastern United States". Anthrozoös. Retrieved 2 March 2021.