A feral animal (from Latin fera, "a wild beast") is an animal living
in the wild but descended from domesticated individuals.
As with an introduced species, the introduction of feral animals or
plants to non-native regions may disrupt ecosystems and has, in some
cases, contributed to extinction of indigenous species. The removal of
feral species is a major focus of island restoration.
4 Species of feral animals
5 Effects of feralization
5.1 Ecological impact
5.2 Genetic pollution
5.3 Economic harm
5.4 Economic benefits
5.5 Scientific value
5.6 Genetic diversity
5.7 Cultural or historic value
6 See also
8 External links
According to dictionary definitions a feral animal is one that has
itself escaped from a domestic or captive status and is living more or
less as a wild animal, or one that is descended from such animals.
Other definitions define a feral animal as one that has changed
from being domesticated to being wild, natural, or untamed. Some
common examples of animals with feral populations are horses, dogs,
goats, cats, and pigs.
Zoologists generally exclude from the "feral" category animals that
were genuinely wild before they escaped from captivity: neither lions
escaped from a zoo nor the sea eagles (Haliaeetus albicilla) recently
re-introduced into the UK are regarded as feral. Wild (i.e.
non-domesticated) species naturalized into a new territory are not
normally considered feral animals.
Alfalfa plants, Medicago sativa, colonize roadsides.
Domesticated plants that revert to wild are referred to as escaped,
introduced, naturalized, or sometimes as feral crops. Individual
plants are known as volunteers. Large numbers of escaped plants may
become a noxious weed. The adaptive and ecological variables seen in
plants that go wild closely resemble those of animals. Feral
populations of crop plants, along with hybridization between crop
plants and their wild relatives, brings a risk that genetically
engineered characteristics such as pesticide resistance could be
transferred to weed plants. The unintended presence of genetically
modified crop plants or of the modified traits in other plants as a
result of cross-breeding is known as "adventitious presence
Stray kitten in Nablus
Certain familiar animals go feral easily and successfully, while
others are much less inclined to wander and usually fail promptly
outside domestication. Some species will detach readily from humans
and pursue their own devices, but do not stray far or spread readily.
Others depart and are gone, seeking out new territory or range to
exploit and displaying active invasiveness. Whether they leave readily
and venture far, the ultimate criterion for success is longevity.
Persistence depends on their ability to establish themselves and
reproduce reliably in the new environment. Neither the duration nor
the intensity with which a species has been domesticated offers a
useful correlation with its feral potential.
Species of feral animals
Feral dogs in Bucharest
The cat returns readily to a feral state if it has not been socialized
when young. These cats, especially if left to proliferate, are
frequently considered to be pests in both rural and urban areas, and
may be blamed for devastating the bird, reptile and mammal
populations. A local population of feral cats living in an urban area
and using a common food source is sometimes called a feral cat colony.
As feral cats multiply quickly, it is difficult to control their
Animal shelters attempt to adopt out feral cats,
especially kittens, but often are overwhelmed with sheer numbers and
euthanasia is used. In rural areas, excessive numbers of feral cats
are often shot. More recently, the "trap-neuter-return" method has
been used in many locations as an alternate means of managing the
feral cat population.
A feral goat in Cornwall
The goat is one of the oldest domesticated creatures, yet readily goes
feral and does quite well on its own.
Sheep are close contemporaries
and cohorts of goats in the history of domestication, but the domestic
sheep is quite vulnerable to predation and injury, and thus rarely
seen in a feral state. However, in places where there are few
predators, they get on well, for example in the case of the Soay
sheep. Both goats and sheep were sometimes intentionally released and
allowed to go feral on island waypoints frequented by mariners, to
serve as a ready food source.
The dromedary camel, which has been domesticated for well over 3,000
years, will also readily go feral. A substantial population of feral
dromedaries, descended from pack animals that escaped in the 19th and
early 20th centuries, thrives in the Australian interior today.
Water buffalo run rampant in Western and Northern Australia. The
Australian government encourages the hunting of feral water buffalo
because of their large numbers.
Cattle have been domesticated since the neolithic era, but can do well
enough on open range for months or even years with little or no
supervision. Their ancestors, the aurochs, were quite fierce, on
par with the modern Cape buffalo. Modern cattle, especially those
raised on open range, are generally more docile, but when threatened
can display aggression. Cattle, particularly those raised for beef,
are often allowed to roam quite freely and have established long term
independence in Australia,
New Zealand and several Pacific Islands
along with small populations of semi-feral animals roaming the
United States and northern Mexico. Such cattle are
variously called mavericks, scrubbers or cleanskins. Most free roaming
cattle, however untamed, are generally too valuable not to be
eventually rounded up and recovered in closely settled regions.
Horses and donkeys, domesticated about 5000 BC, are feral in open
grasslands worldwide. In Portugal, feral horses are called Sorraia; in
Australia, they are called Brumbies; in the American west, they are
called mustangs. Other isolated feral populations exist, including the
Chincoteague Pony and the Banker horse. They are often referred to as
"wild horses," but this is a misnomer. There are truly "wild" horses
that have never been domesticated, most notably Przewalski's horse.
While the horse was originally indigenous to North America, the wild
ancestor died out at the end of the last Ice Age. In both Australia
and the Americas, modern "wild" horses descended from domesticated
horses brought by European explorers and settlers that escaped,
spread, and thrived.
Australia hosts a feral donkey population, as do
Virgin Islands and the American southwest.
The pig (hog) has established feral populations worldwide, most
notably in Australia, New Zealand, the United States,
New Guinea and
the Pacific Islands. Pigs were introduced to the Melanesian and
Polynesian regions by humans from several thousand to five hundred
years ago, and to the Americas within the past 500 years. In
Australia, domesticated pigs escaped in the 18th century, and now
cover 40 percent of Australia with a population estimated at 30
million. While pigs were doubtlessly brought to
New Zealand by the
original Polynesian settlers, this population had become extinct by
the time of European colonization, and all feral pigs in New Zealand
today are descendants of European stock. Many European wild boar
populations are also partially descended from escaped domestic pigs
and are thus technically feral animals within the native range of the
Rock doves, also known as pigeons: feral animals who nonetheless live
in close proximity to humans
Barbary dove in Tasmania, Australia. Also known as a ringneck
dove or ring dove (Streptopelia risoria)
Rock pigeons were formerly kept for their meat or more commonly as
racing animals and have established feral populations in cities
Colonies of honey bees often escape into the wild from managed
apiaries when they swarm; their behavior, however, is no different
from their behavior "in captivity", until and unless they breed with
other feral honey bees of a different genetic stock, which may lead
them to become more docile or more aggressive (see Africanized bees).
Large colonies of feral parrots are present in various parts of the
world, with rose-ringed parakeets, monk parakeets and red-masked
parakeets (the latter of which became the subject of the documentary
film, The Wild Parrots of Telegraph Hill) being particularly
successful outside of their native habitats and adapting well to
Effects of feralization
See also: Rewilding (conservation biology)
A feral population can have a significant impact on an ecosystem by
predation on vulnerable plants or animals, or by competition with
indigenous species. Feral plants and animals constitute a significant
share of invasive species, and can be a threat to endangered species.
However, they may also replace species lost from an ecosystem on
initial human arrival to an area, or increase the biodiversity of a
human-altered area by being able to survive in it in ways local
Main article: Genetic pollution
Animals of domestic origin sometimes can produce fertile hybrids with
native, wild animals which leads to genetic pollution (not a clear
term itself) in the naturally evolved wild gene pools, many times
threatening rare species with extinction. Cases include the mallard
duck, wild boar, the rock dove or pigeon, the red junglefowl (Gallus
gallus) (ancestor of all chickens), carp, and more recently
salmon. Other examples of genetic swamping lie in the breeding
history of dingoes. Dingoes are wild true dogs that will interbreed
with dogs of other origins, thus leading to the proliferation of dingo
hybrids and the possibility of the extinction of pure wild
dingoes. Researches in
Scotland have remarked on a similar
phenomenon of the genetic mixing of feral domestic cats and their wild
counterparts. In some cases like rabbits, genetic pollution seems
not to be noticed. There is much debate over the degree to which feral
hybridization compromises the purity of a wild species. In the case of
the mallard, for example, some claim there are no populations that are
completely free of any domestic ancestor.
Feral animals compete with domestic livestock, and may degrade fences,
water sources, and vegetation (by overgrazing or introducing seeds of
invasive plants). Though hotly disputed, some cite as an example the
competition between feral horses and cattle in the western United
States. Another example is of goats competing with cattle in
Australia, or goats that degrade trees and vegetation in
environmentally-stressed regions of Africa. Accidental crossbreeding
by feral animals may result in harm to breeding programs of pedigreed
animals; their presence may also excite domestic animals and push them
to escape. Feral populations can also pass on transmissible infections
to domestic herds. Loss to farmers by aggressive feral dog population
is common in India.
Many feral animals can sometimes be captured at little cost and thus
constitute a significant resource. Throughout most of
Melanesia feral pigs constitute the primary sources of animal protein.
Prior to the Wild and Free-Roaming Horses and Burros Act of 1971,
American mustangs were routinely captured and sold for horsemeat. In
Australia feral goats, pigs and dromedaries are harvested for the
export for their meat trade. At certain times, animals were sometimes
deliberately left to go feral, typically on islands,
in order to be later recovered for profit or food use for travelers
(particularly sailors) at the end of a few years.
Populations of feral animals present good sources for studies of
population dynamics, and especially of ecology and behavior (ethology)
in a wide state of species known mainly in a domestic state. Such
observations can provide useful information for the stock breeders or
other owners of the domesticated conspecifics (i.e. animals of the
Feral populations sometimes preserve or develop characteristics which
do not always exist in the fully domesticated equivalent. Therefore,
they contribute to domestic biodiversity and often deserve to be
preserved, be it in their feral environment or as domestic animals.
For example, feral species that are usually subjects of eradication in
New Zealand are currently the subject of study to
determine if there is a need for their preservation.
Cultural or historic value
American mustangs have been protected since 1971 in part due to their
romance and connection to the history of the American West. A similar
situation is that of the
Danube Delta horse from the
Letea Forest in
the Danube Delta. Romanian government is considering the protection of
the feral horses and transforming them into a tourist attraction,
after it first approved the killing of the entire population. Due to
the intervention of numerous organizations and widespread popular
disapproval of the
Romanians the horses have been saved, but still
have an uncertain fate as their legal status is unclear and local
people continue to claim the right to use the horses in their own
Overpopulation in companion animals
Stray dogs in Bangkok
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Look up feral animal in Wiktionary, the free dictionary.
Horse and Burro Program
Feral Camels, Information from Australian Department of Agriculture
regarding Australia's estimated 300,000 feral camels.
Cat Allies, a feral cat advocacy