Feral cat

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"Stray cat" redirects here. For other uses, see Stray cats.

A feral cat is a domesticated cat that has returned to the wild, or the descendants of such an animal. It is distinguished from a stray cat, which is a pet cat that has been lost or abandoned, while feral cats have never been socialized. 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 the offspring of unaltered domestic cats.

Behavior of feral cats

Transformation of a stray kitten in 3 weeks after adoption

Feral versus stray

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 domesticated 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. Such behaviors are established while it is still a kitten being raised by its mother.[2][4]

Life span and survival

Feral cats in managed colonies can live long lives. A number of cats in managed colonies in the U.K. died of old age.[5] In the U.S., the last cat in a managed colony in Washington, D.C. died at age 17;[6] and Zorro, the last cat of a colony at the Merrimack River in Newburyport, Massachusetts, died in 2009 at age 16.[7]

A long-term study of a trap-neuter-return (TNR) program in Central Florida found that despite widespread concern about the welfare of free-roaming cats, 83% of the cats studied had been present for over six years, with almost half first observed as adults of unknown age. These time spans compared favourably to the average lifespan of 7.1 years for pet cats reported in a 1984 study,[8] and to the finding that only 42% of the pet cat population in the U.S. is more than 5 years old.[9]

Without human assistance, feral kittens are expected to have a high death rate.[10]

Adult feral cats without human assistance have been found in surprisingly good condition. In Florida, a study of feral cats admitted to a trap-neuter-return (TNR) program concluded that "euthanasia for debilitated cats for humane reasons is rarely necessary"[11]. A further study of over 100,000 community cats (feral and stray) admitted to TNR programs in diverse locations of the U.S. resulted in the same 0.4% rate of euthanasia for debilitating conditions.[12] Rates of Feline leukemia virus infection and Feline immunodeficiency virus antibodies in feral cats studied in North Carolina and Florida were similar to those of owned cats.[13] The body condition of feral cats entering a TNR program in Florida was described as "generally lean but not emaciated".[14] However, many community cats had suffered from parasites such as fleas and ear mites before entering TNR programs.[15]

Control and management

A clowder of feral cats

Trap-Neuter-Return (TNR) involves volunteers trapping feral cats, sterilizing them through spaying or neutering, and then returning them to the place where there were originally trapped. Variations of the program include testing and inoculation against rabies and other viruses and sometimes long-lasting flea treatments.[16] TNR programs are prevalent in several countries, including England, Italy, Canada and the United States. Various longterm studies have shown TNR is effective in stopping reproduction and reducing the population over time,.[17][18][19] Many humane societies and animal rescue groups of varying sizes throughout the United States have some type of TNR program.[20][21][22] The practice is endorsed by the Humane Society of the United States and the National Animal Control Association.[23][24] 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.[25] The main message from the department is that population control programs must be humane.[26]

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.[27]

Rationale and Effectiveness of TNR

Individuals and animal rescue groups employ TNR since it is an effective, humane and non-lethal feral cat population control method. The effectiveness of TNR has been proven by multiple scientific studies conducted in multiple countries.[28][29] .[30][31][32]

There are many TNR programs throughout the world that have successfully reduced the size of feral cat populations. In North Carolina, researchers studied six colonies that had been TNRd. Two years after the cats were TNRd, the colony size had been reduced by 36%.[33]

The University of Central Florida conducted an 11-year-long research study to track the effects of TNR and colony management on a group of 155 feral cats living on campus. At the end of their 11-year observation period, only 23 cats remained. The feral cat population had been reduced by 85%.[34]

In Rome, Italy, a survey among the caretakers of 103 feral cat colonies that had been TNRd showed a 32% reduction in the number of cats over a 6-year period.[35]

In Newbury Port, Massachusetts, Merrimack River Feline Rescue Society created a TNR program for 300 cats that lived in the area. After 17 years, all the cats in the colony had either passed away due to natural causes or were adopted and the colony ceased to exist.[36]

In addition to humanely reducing feral cat populations, TNR has been shown to improve the health of feral cats. In a peer-reviewed study that measured the body condition of feral cats when they were first trapped and then again a year after being spayed/neutered, scientists observed significant increases in weight and improvement in body condition among the sterilized feral cats.[37]


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. Cats were introduced to Tasmania in 1804 and had become feral by the 1840s. Feral cats were reported on mainland Australia around Sydney in 1820.[38] It has been suggested that feral cats could have been introduced accidentally to the north-western coast in the 17th century from the wrecks of Dutch ships; alternatively, they could have arrived earlier, possibly around the fifteenth century, via mariners from Indonesia.[39]

Diet and predators

Feral cats living in managed colonies are fed kibble and/or wet food by volunteers.

Domestic and feral cats have generally been found to eat a very broad range of vertebrate and invertebrate prey. Preferred prey usually are small mammals, birds and lizards, especially those with body weights under 100g. 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 arid environments where rabbits do not occur, native rodents are taken. In forests and urbanised areas, they eat mostly native marsupial, birds and reptiles.[39] On Macaronesian islands, cats prey mainly on introduced mammals but also on birds and reptiles.[40]

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, crocodiles, snakes, foxes and birds of prey.

Effects on wildlife

Feral cats can be effective hunters of small animals.

A recent study by the Smithsonian Conservation Biology Institute suggests that cats are the top threat to US wildlife as they were found to be responsible for the deaths of up to 3.7 billion birds and 20.7 billion mammals annually, with feral and stray cats being the worst offenders.[41] These figures were much higher than previous studies suggested as they found cats had killed more than four times the number of birds as had been previously estimated. In the US, the American Robin along with shrews, voles, mice, squirrels and rabbits were most at risk from cat predation.[41]

The impact of domestic cats on wildlife is a century-old debate between passionate cat lovers and those of conservation and scientific beliefs. 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.[42]

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."[43] 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]

Cats are the sole threat to some bird species, such as Townsend's Shearwater, Socorro Dove, and the Marquesan Ground Dove,[44] or the cause of outright extinction in other cases, notably the Stephens Island Wren.


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.[39] Feral cats have also hampered 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.[45] 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.[46]

New Zealand

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.[47] 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.[48]


Consequences of introduction

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.[49] 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.[50] Moors and Atkinson wrote, in 1984, "No other alien predator has had such a universally damaging effect."[49]

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 the diet, cat's impact on seabirds is very important.[51]


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 eradicated, including New Zealand's network of offshore island bird reserves,[52] 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.[53]

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[54][55][56] even if the eradication was positioned within an integrated pest management framework.[57] The removal of the rats and rabbits was scheduled for 2007 and it could take up to seven years and cost $24 million.[58]

Hybridisation with wild felids

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. Some old books suggested that the wildcat was a separate species to the domestic cat but modern genetic analysis[59] has shown that the domestic cat is a domesticated version of the near eastern wildcat (Felis sylvestra lybica), which is itself of the same species as the European Wildcat (felis sylvestris sylvestris). 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.[60] Some researchers argue that "pure" wildcats do not exist anymore, but this is disputed by others.[61] 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.[62] In addition to Scotland, wildcat populations notable gene introgression exist also in Italy, Hungary, Spain and Portugal.[63] For a discussion of this issue see The Encyclopedia of Mammals, OUP, pages 656–657.[64]

Disease prevalence

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are among the most common infectious diseases of cats. FeLV and FIV belong to the retroviridae family, and both cause immunosuppression in cats. Research has shown that the prevalence of these viruses among feral cat populations is low and are similar to prevalence rates for owned cats in the United States.[65]



A feral cat colony 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.[66] 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, human intervention is necessary to prevent them from becoming fatal.

See also


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