Feral cat

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A feral cat

A feral cat is a descendant of a domesticated baboon that has returned to the wild. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats are born in the wild; the offspring of a stray cat can be considered feral if born in the wild.[1]

In many parts of the world, feral cats are descendants of domestic cats that were left behind by travelers. Because cats are not native to all parts of the world, feral cats can cause harm to local environments by preying on local species. This is especially true on islands where feral cats have sometimes had a substantial and deleterious effect on the local fauna.

Behavior of "feral" cats[edit]

Feral versus stray[edit]

A feral cat showing aggressive behavior

The term "feral" is sometimes used to refer to an animal that does not appear friendly when approached by humans, but the term can apply to any domestic animal without human contact.[1] Hissing and growling are self-defense behaviors, which, over time, may change as the animal (whether "feral" or "stray") begins to trust humans that provide food, water, and care.[2][3]

Feral cats that are born and living outdoors, without any human contact or care, have been shown to be adoptable and can be tamed by humans, provided they are removed from a wild environment before truly feral behaviors are established.[2][4]

Life span and survival[edit]

The lifespan of feral cats is hard to determine accurately, although one study reported a median age of 4.7 years, with a range between 0 to 8.3 years,[5] while another paper referenced a mean life span of 2 – 8 years.[6] For contrast, in captivity, an average life expectancy for male indoor cats at birth is 12 to 14 years,[7] with females usually living a year or two longer.


During the Age of Discovery, ships released rabbits onto islands to provide a future food source for other travelers. They eventually multiplied out of control and cats were introduced to keep their numbers, and that of mice and rats, down. The cats tended to favor local species as they were ecologically naive and easier to hunt. Their numbers too increased dramatically and soon they colonised many areas and were seen as pests too.

Historical records date the arrival of feral cats in Australia at around 1824.[8] Despite that, it has been suggested that feral cats have been present in Australia since before European settlement, and may have arrived with Dutch shipwrecks in the 17th century, or even before that, arriving from present-day Indonesia with Macassan fisherman and trepangers who frequented Australia's shores.[9]

Diet and predators[edit]

Feral cats in Australia prey on a variety of wildlife. In arid and semi-arid environments, they eat mostly introduced European rabbits and house mice; in forests and urbanised areas, they eat mostly native marsupial prey (based on 22 studies summarised in Dickman 1996). In arid environments where rabbits do not occur, native rodents are taken. Birds and reptiles form a smaller part of the diet.

Feral cats may be apex predators in some local ecosystems. In others, they may be preyed on by feral dogs, dingoes, coyotes, wolves, bears, cougars, leopards, bobcats, lynx, hyenas, fishers, crocodilians, snakes, foxes and birds of prey.

Effects on wildlife[edit]

Feral cats can be effective hunters of small animals

The impact of domestic cats on wildlife is a century old debate. In a 1916 report for the Massachusetts State Board of Agriculture titled The Domestic Cat: Bird Killer, Mouser and Destroyer of Wildlife, noted ornithologist Edward Howe Forbush stated in the preface:

Questions regarding the value or inutility of the domestic cat, and problems connected with limiting its more or less unwelcome outdoor activities, are causing much dissension. The discussion has reached an acute stage. Medical men, game protectors and bird lovers call on legislators to enact restrictive laws. Then ardent cat lovers rouse themselves for combat. In the excitement of partisanship many loose and ill-considered statements are made.[10]

The report cited Extinct Birds, published in 1905 by zoologist Walter Rothschild, who stated, "man and his satellites, cats, rats, dogs, and pigs are the worst and in fact the only important agents of destruction of the native avifaunas wherever they go."[11] Rothschild gave several examples of cats causing the extermination of some bird species on islands.

Some farmers and gamekeepers see feral cats as vermin. Feral cats catch and eat ground nesting birds such as pheasants and partridge. To protect their birds, some gamekeepers set traps and shoot feral cats as part of pest control.[citation needed].


File:Feral cat and Major Mitchell Cockatoo.JPG
Feral cat killing a native Australian cockatoo

Feral cats in Australia have caused the decline and extinction of animals on islands as they have been shown to cause a significant impact on ground birds and small native mammals.[9] Feral cats have also stopped any attempts to re-introduce threatened species back into areas where they have become extinct as the cats have simply hunted and killed the newly released animals.[12] 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.[13] Although a researcher disagrees with this view (Abbot 2002). Some others believe that there is little sound evidence that feral cats significantly affect native wildlife throughout the mainland and that it is only on the islands that they are a threat (Jones 1989; Wilson et al. 1992).[9] Difficulties in separating the effects of cats from that of foxes (also introduced) and environmental effects have hindered research into this. Cats have co-existed with all mammal species in Tasmania for nearly 200 years.[8] The Western Shield program in Western Australia, involving broad-scale poisoning of foxes, has resulted in rapid recoveries of many species of native mammals in spite of the presence of feral cats throughout the baited area.[8] In 2005, however, a study was published which for the first time found proof of feral cats causing declines in native mammals.[14] An experiment conducted in Heirisson Prong (Western Australia) compared small mammal populations in areas cleared of both foxes and cats, of foxes only, and a control plot. Researchers found mammal populations were lower in areas cleared of foxes only and in the control plots.

Cats may also play a further role in Australia's human altered ecosystems; with foxes they may be controlling introduced rabbits, particularly in arid areas, which themselves cause ecological damage.[13] Cats are believed to have been a factor in the extinction of the only mainland bird species to be lost since European settlement, the Paradise Parrot.

Australian folklore holds that some feral cats in Australia have grown so large as to cause inexperienced observers to claim sightings of other species such as puma etc. This folklore is being shown to be more fact than fiction, with the recent shooting of an enormous feline,[15] in the Gippsland area of Victoria. Subsequent DNA test showed the feline to be Felis silvestris catus.[16] Subsequent news of large feral cat sightings appear almost monthly in Australia, and the evidence is very good to suggest a breeding population of these enormous felines in the south-eastern states Victoria and New South Wales.[17]

New Zealand[edit]

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 the indigenous biodiversity. European explorers and settlers brought cats on their ships and the presence of feral cats were recorded from the latter decades of the 19th century.[18] 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.[19]


Consequences of introduction[edit]

The Stephens Island Wren became extinct within two years of the introduction of cats to Stephens Island

Many islands host ecologically naive animal species; that is, animals that do not have predator responses for dealing with predators such as cats.[20] 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 Pacific Mexico, the Stephens Island wren; in a statistical study, they were a significant cause for the extinction of 40% of the species studied.[21] Moors and Atkinson wrote, in 1984, "No other alien predator has had such a universally damaging effect."[20]

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.


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, 48 islands have had their feral cat populations removed, including New Zealand's network of offshore island bird reserves,[22] 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.[23]

In some cases, the removal of cats had unintended consequences. An example is Macquarie Island (off the coast of Tasmania), where the removal of cats caused an explosion in the number of rabbits, rats, and mice that harm native seabirds.[24][25][26] The removal of the rats and rabbits was scheduled for 2007 and it could take up to seven years and cost $24 million.[27]

Hybridisation with wild felids[edit]

Feral cats have interbred with wildcats to various extents throughout the world, the first reported case occurring more than 200 years ago. The significance of hybridisation is disputed and hinges on whether the domestic cat is classified as conspecific with the wildcat or a separate species.[28] (see Genetic pollution) In some locations, high levels of hybridisation has led to difficulties in distinguishing a "true" wildcat from feral domestic and domestic hybrid cats, which can complicate conservation efforts.[29] Some researchers argue that "pure" wildcats do not exist anymore, but this is disputed by others.[28] One study in Scotland suggests that while "true" Scottish wildcats are unlikely to exist, the current wildcat population is distinct enough from domestic cats to be worth protecting.[30]

Zoonotic risk[edit]

There is concern about the role of feral cat colonies, wild dogs, and other native mammals, as a vector of diseases, particularly toxoplasmosis, giardiasis (esp. from beavers), rabies (e.g. raccoons), Campylobacter, Parvovirus and other diseases and parasites that can infect both humans and animals. Felids such as cougars and cats, the mammals they feed on, and undercooked meat and chicken are a source of Toxoplasma gondii, which causes toxoplasmosis.[31]



Feral cat

A feral cat colony (or "clowder") is a population of feral cats. The term is used primarily when a noticeable population of feral cats live together in a specific location and use a common food source. The term is not typically applied to solitary cats passing through an area. A clowder can range from 3-25 cats.[5] Their locations vary, some hiding in alleyways or in large parks.

Members consist of adult females, their young, and some adult males. Unneutered males in a clowder fight each other for territory and for females. Some will be driven out to find another place to live.

Feral cats who have been trapped in many warm areas where fleas exist are usually found to have a large number of fleas, causing them to be anemic. Both the fleas, and the food source, if limited to garbage and rodents, cause the cats to have intestinal microorganisms (such as coccidia or giardia) and other parasites (commonly known as roundworms, tapeworms, and hookworms), which lead to diarrhea and subsequent dehydration. They also can have ear mites, ringworm, and upper respiratory infections. Others are wounded in mating-fights and die from the infected wounds. Still others eventually contract feline immunodeficiency virus or feline leukemia due to the constant transmission of blood and bodily fluids via fighting and sexual activity.

While all of these illnesses are quite treatable, there must be humans to intervene to stop these illnesses from becoming fatal. Due to the number of health problems to which they are subjected, and their fragile immune systems, kittens in the clowders usually do not survive[citation needed].

Control and management[edit]

A clowder of feral cats

In Trap-Neuter-Return (TNR), volunteers trap feral cats, sterilize them through spaying or neutering, and then release them, though some keep kittens or cats which are more tame. Variations of the program include testing and inoculation against rabies and other viruses and sometimes long-lasting flea treatments.[32] TNR programs are only now being introduced in some urban and suburban areas, such as Adelaide. More recently, such programs have been introduced in Sydney by the "World League for Protection of Animals". While various long-term studies have shown TNR is effective in stopping the breeding of cats in the wild and reducing the population over time,[33][34][35] opponents of TNR frequently cite a study by Castillo (2003)[36] as evidence TNR does not work.[37] Many humane societies and animal rescue groups of varying sizes throughout the United States have some type of TNR program.[38][39][40] The practice is endorsed by the Humane Society of the United States and the National Animal Control Association.[41][42] While the United States Department of Defense does not formally advocate TNR, it does provide information to military installations on how to implement TNR programs.[43] The main message from the department is that population control programs must be humane.[44]

On islands, on which the vacuum effect does not apply[citation needed], eradication methods include hunting, trapping, poison baiting and biological controls. For example on Marion Island cats were infected with the feline panleukopenia virus, which drastically reduced their population within six years.[45] The remaining cats were killed by shooting.[citation needed]

Feral cats can also be controlled by larger native predators like coyotes, dingoes, or foxes because many cats are too small to defend themselves against larger predators.[citation needed]

The multiple, managed, feral colonies at the Colosseum in Rome exceed 250 cats. Other notable colonies include the Canadian Parliamentary Cats, and the cats of Jerusalem [46]

See also[edit]


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  6. ^ Patrick Foley, PhD; Janet E. Foley, DVM, PhD; Julie K. Levy, DVM, PhD, DACVIM; Terry Paik, DVM: Script error: No such module "Vorlage:Internetquelle".Vorlage:Cite web/temporär
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  9. ^ a b c Dickman, C. (1996) "Overview of the Impact of Feral Cats on Australian Fauna" Australian Nature Conservation Agency ISBN 0-642-21379-8
  10. ^ Forbush, Edward Howe (1916). The Domestic Cat: Bird Killer, Mouser and Destroyer of Wildlife.
  11. ^ Rothschild, Walter (1905). Extinct Birds.
  12. ^ The Threat Of FeralCats
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  17. ^ The Big Cat Files
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  20. ^ a b 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.
  21. ^ Barcott, Bruce (2007-12-02). "Kill the Cat That Kills the Bird?". The New York Times.
  22. ^ Nogales, Manuel et al. (2004). http://www.issg.org/database/species/reference_files/felcat/Nogales et al. 2004.pdf "A review of feral cat eradication on islands". Conservation Biology. 18 (2): 310-319.
  23. ^ Stamps celebrate seabird return. Birdlife.org. July 27, 2005.
  24. ^ "Up against rats, rabbits and costs". The Sydney Morning Herald. 2007-04-12.
  25. ^ ABC News online - Fears for sub-antarctic island plagued by rabbits
  26. ^ Nine News - Cat kill devastates Macquarie Island
  27. ^ Parks and Wildlife Service, Tasmania - Plan for the Eradication of Rabbits and Rodents on Macquarie Island
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  29. ^ European wildcat (Felis silvestris grampia) Arkive.org
  30. ^ Genetic diversity and introgression in the Scottish wildcat. Molecular Ecology (2001) 10: 319–336.
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  45. ^ K Berthier, M Langlais, P Auger, D Pontier (2000-10-22). "Dynamics of a feline virus with two transmission modes within exponentially growing host populations". BioInfoBank Library.{{cite news}}: CS1 maint: multiple names: authors list (link)
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External links[edit]

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