Effects of an Invasive Species: Domestic Cats Fact Sheet by the Wildlife Society in 2017
Feral and free-ranging domestic cats are exotic species to North
America. Exotic species are recognized as one of the most widespread and
serious threats to the integrity of native wildlife populations and
natural ecosystems. Exotic species present special challenges for
wildlife managers because their negative impacts on native species are
poorly understood by the public to the point that many exotic species
are perceived as a natural component of the environment. Some exotic
species have advocacy groups that promote their continued presence, and
few policies and laws deal directly with their control. Perhaps no issue
has captured more of the challenges for contemporary wildlife
management than the impacts of feral or free-ranging domestic cats and
their impacts on native wildlife.
Domestic cats originated from an ancestral wild species, the European and African wild cat (Felis silvestris). The domestic cat (Felis catus)
is now considered a separate species, and is found on all 7 continents,
with 600 million cats worldwide and 148-188 million within the U.S..
Domestic cats have great reproductive potential. Individuals become
sexually mature as early as 6 months of age, and reproduction can occur
throughout the year. A single female may produce as many as 3 litters
each year with 2 to 4 kittens per litter, with the capacity to
successfully raise as many as 12 offspring in any given year.
A growing body of literature strongly suggests that domestic cats are
significant predators on small mammals, birds, reptiles, and
amphibians. Feral and free-ranging cats also serve as reservoirs for
several diseases, including rabies, toxoplasmosis, bartonellosis,
typhus, and feline immunodeficiency virus, that can have significant
effects on the health of humans, wildlife, and other domestic animals.
Because humans often feed free-ranging cats, they can reach population
levels that may result in abnormally high predation rates on wildlife
and increase the spread of diseases. Domestic cats have tremendous
impacts on wildlife and are responsible for the extinction of numerous
mammals, reptiles, and at least 33 bird species globally. Effects of cat
predation and disease spread are most pronounced in island settings
(both actual islands and islands of habitat), where populations of
wildlife are already low or stressed by other factors. Effects are also
significant in natural areas where cat colonies become established.
Competition with native predators, disease implications for native
wildlife populations, and pet owners’ attitudes toward wildlife and
wildlife management also are important issues.
Extensive popular debate over absolute numbers or types of prey taken
by feral and free-ranging cats is not productive. The number of cats is
undeniably large. Even if conservative estimates of prey taken are
considered, the number of prey animals killed is immense. The
supplemental feeding of cats does not deter them from killing wildlife;
often they do not eat what they kill. Likewise, population-level impacts
of diseases associated with cats have only been established in a few
wildlife species, such as southern sea otters (Enhydra lutris nereis),
but negative individual impacts clearly occur in an extremely wide
range of species. Humans introduced cats to North America, and humans
are ultimately responsible for the effects these animals have on native
wildlife species.
The policy of The Wildlife Society regarding feral and free-ranging domestic cats is to:
- Support and encourage the humane elimination of feral cat
populations, including feral cat colonies, through adoption into
indoor-only homes of eligible cats and humane euthanasia of unadoptable
cats.
- Support the passage and enforcement of local and state ordinances
prohibiting the feeding of feral cats, especially on public lands, and
the release of unwanted pet or feral cats into the wild.
- Oppose the passage of any local or state ordinances that legalize
the maintenance of “managed” (trap/neuter/release) free-ranging cat
colonies.
- Support educational programs and materials that provide scientific
information on feral cats and the negative effects on cats from living
outdoors, and call on pet owners to keep cats indoors, in outdoor
enclosures, or on a leash.
- Support programs to educate and encourage pet owners to neuter or
spay their cats, and encourage all pet adoption programs to require
potential owners to spay or neuter their pet.
- Support the development and dissemination of information on what
individual cat owners can do to minimize predation by free-ranging cats,
and to minimize potential disease transmission to humans, wildlife,
cats, and other domestic animals.
- Pledge to work with the conservation and animal welfare communities
to educate the public about the effects of free-ranging and feral cats
on native wildlife, including birds, small mammals, reptiles,
amphibians, and endangered species.
- Support educational efforts to encourage the agricultural community
to keep farm-cat numbers at low, manageable levels and use alternative,
environmentally safe rodent control methods.
- Support efforts to reduce risks to the health of humans and other
animals posed by diseases and parasites of feral cats, including but not
limited to removal of free-ranging cats and elimination of feral cat
colonies. Encourage researchers to develop, obtain, and disseminate
information on the impacts of feral and free-ranging cats on native
wildlife populations, relative to predation, competition, and diseases.
- Recognize that cats as pets have a long association with humans, and
that responsible cat owners are to be encouraged to continue caring for
the animals under their control.
The Wildlife Society’s Position Statement on Invasive and Feral Species
states that the Society opposes “introduction or maintenance of
invasive species and feral species that threaten the survival of
indigenous species” (TWS 2016).
Feral and Free-Ranging Domestic Cats Issue Statement pdf
