Cats and Wildlife A Conservation Dilemma; By John S.
Coleman, Stanley A. Temple and Scott R. Craven
source:
http://wildlife.wisc.edu/extension/catfly3.htm
Domestic cats first arrived in North America with European
colonists several hundred years ago. Since that time, cats have multiplied and
thrived as cherished pets, unwanted strays, and semi-wild predators. Although
often overlooked as a problem, free-ranging cats affect other animals, often far
from the homes and farms they share with people. Because we brought the domestic
cat to North America, we have a responsibility to both the cats and to the wild
animals they may affect. Here are some interesting and perhaps surprising facts
concerning the contemporary dilemma posed by free-ranging domestic cats in the
United States.
How cats became domesticated
Domestic cats originated from an ancestral wild species,
Felis silvestris, the European and African Wild Cat. The domestic cat is now
considered a separate species, named Felis catus. In appearance, domestic cats
are similar to their wild relatives, and many of their behaviors, such as
hunting and other activity patterns, remain essentially unchanged from their
ancestral form. Cats were first domesticated in Egypt around 2000 BC [1].
Domestic cats spread slowly to other parts of the globe, possibly because
Egyptians prevented export of the animal they worshiped as a goddess. However,
by 500 BC the Greeks had acquired domestic cats, and they spread cats throughout
their sphere of influence. The Romans introduced the domestic cat to Britain by
300 AD. Domestic cats have now been introduced around the world, mostly by
colonists from Europe.
How many cats are there in the United States?
The estimated numbers of pet cats in urban and rural
regions of the United States have grown from 30 million in 1970 [2] to 60
million in 1990 [3]. These estimates are based on U.S. Census data and include
only those cats that people claim to "own" as pets, not cats that are
semi-wild or free-ranging. Nationwide, approximately 30% of households have
cats. In rural areas where free-ranging cats are usually not regarded as pets,
approximately 60% of households have cats. In the state of Wisconsin alone, with
approximately 550,000 rural households, the number of rural free-ranging cats
(not house pets) may be as high as 2 million [4]. The combined total of pets and
free-ranging cats in the U.S. is probably more than 100 million. Because of
their close association with humans, most of these cats are concentrated in
areas where people live rather than in remote undeveloped areas.
The legal status of domestic cats
The laws that relate to domestic cats vary by local
government. In most areas, the person who provides care for a cat is legally
responsible for its welfare and control. As with other domestic animals, if
ownership can be established by collars or other means of identification, a cat
is considered personal property [5]. It is usually the responsibility of the
owner to control the cat's movements. In most areas, cats can be live trapped
and either returned to the owner or turned over to authorities if they wander
onto other peoples' property. Many municipalities have leash laws and require
vaccination and neutering of pet cats. Because laws vary, one should check local
ordinances for the appropriate way to deal with stray cats.
What effects do domestic cats have on wildlife?
Although rural free-ranging cats have greater access to
wild animals and undoubtedly take the greatest toll, even urban house pets take
live prey when allowed outside. Extensive studies of the feeding habits of
free-ranging domestic cats over 50 years and four continents [6] indicate that
small mammals make up approximately 70% of these cats' prey while birds make up
about 20%. The remaining 10% is a variety of other animals. The diets of
free-ranging cat populations, however, reflect the food locally available.
Observation of free-ranging domestic cats shows that some
individuals can kill over 1000 wild animals per year [7], although smaller
numbers are more typical. Some of the data on kills suggest that free-ranging
cats living in small towns kill an average of 14 wild animals each per year.
Rural cats kill many more wild animals than do urban, or suburban cats [8].
Several studies found that up to 90% of free-ranging rural cats' diet was wild
animals, and less than 10% of rural cats killed no wild animals [9]. Recent
research [10] suggests that rural free-ranging domestic cats in Wisconsin may be
killing between 8 and 217 million birds each year. The most reasonable estimates
indicate that 39 million birds are killed in the state each year. Nationwide,
rural cats probably kill over a billion small mammals and hundreds of millions
of birds each year. Urban and suburban cats add to this toll. Some of these
kills are house mice, rats and other species considered pests, but many are
native songbirds and mammals whose populations are already stressed by other
factors, such as habitat destruction and pesticide pollution.
Despite the difficulties in showing the effect most
predators have on their prey, cats are known to have serious impacts on small
mammals and birds. Worldwide, cats may have been involved in the extinction of
more bird species than any other cause, except habitat destruction. Cats are
contributing to the endangerment of populations of birds such as Least Terns,
Piping Plovers and Loggerhead Shrikes.
In Florida, marsh rabbits in Key West have been threatened by predation from
domestic cats [11]. Cats introduced by people living on the barrier islands of
Florida's coast have depleted several unique species of mice and woodrats to
near extinction [12, 13].
Not only do cats prey on many small mammals and birds, but
they can outnumber and compete with native predators. Domestic cats eat many of
the same animals that native predators do. When present in large numbers, cats
can reduce the availability of prey for native predators, such as hawks [14] and
weasels [15].
Free-ranging domestic cats may also transmit new diseases to wild animals. Domestic cats have spread feline leukemia virus to mountain lions [16] and may have recently infected the endangered Florida Panther with feline panleukopenia (feline distemper) and an immune deficiency disease [17]. These diseases may pose a serious threat to this rare species. Some free-ranging domestic cats also carry several diseases that are easily transmitted to humans, including rabies and toxoplasmosis [18].
Domestic cats vs. native predators
Although cats make affectionate pets, many domestic cats
hunt as effectively as wild predators. However, they differ from wild predators
in three important ways: First, people protect cats from disease, predation and
competition, factors that can control numbers of wild predators, such as
bobcats, foxes, or coyotes. Second, they often have a dependable supply of
supplemental food provided by humans and are, therefore, not influenced by
changes in populations of prey. Whereas populations of native predators will
decline when prey becomes scarce, cats receiving food subsidies from people
remain abundant and continue to hunt even rare species. Third, unlike many
native predators, cat densities are either poorly limited or not limited by
territoriality [19]. These three factors allow domestic cats to exist at much
higher densities than native predators. In some parts of rural Wisconsin,
densities of free-ranging cats reach 114 cats per square mile. In these areas,
cats are several times more abundant than all mid-sized native predators (such
as foxes, raccoons, skunks) combined. With abundant food, densities can reach
over 9 per acre, and cats often form large feeding and breeding
"colonies" (81 cats were recorded in one colony, and colonies of over
20 are not uncommon) [20, 21]. Unlike some predators, a cat's desire to hunt is
not suppressed by adequate supplemental food. Even when fed regularly by people,
a cat's motivation to hunt remains strong, so it continues hunting [22].
In summary
Free-ranging cats are abundant and widespread predators.
They often exist at much higher densities than native predators. They prey on
large numbers of wild animals, some of which are rare or endangered. They
compete with native predators, and they harbor a variety of diseases. Yet, cats
are popular pets. In order to have and care for our pets--and still protect our
native wildlife--we must make an effort to limit in a humane manner the adverse
effects free-ranging cats can have on wildlife.
What you can do
 |
Keep only as many pet cats as you can feed and care for.
Controlling reproduction and humanely euthanizing unwanted cats will keep cat
populations from growing beyond the size that can be adequately cared for. On
farms, keep only the minimum number of free-ranging cats needed to control
rodents. Well-fed, neutered females will stay closest to farm buildings and
do most of their killing where rodent control is needed most. Traps and
rodenticides, as well as rodent-proof storage and construction, will usually
contribute more to effective rodent control than cats. |
|
If at all possible, for the sake of your cat and local
wildlife, keep your cat indoors. Confinement will eliminate unwanted
reproduction, predation on wild animals, and the spread of disease. Bells are
mostly ineffective in preventing predation [23] because, even if the bell rings,
it's usually too late for the prey being stalked. Declawing may reduce hunting
success, but many declawed cats are still effective predators. Keeping your cats
indoors helps protect the wildlife around your yard and prevents your cat from
picking up diseases from strays or getting injured. The two most common causes
of death for rural cats in south central Wisconsin are disease and being struck
by automobiles. If cats must be allowed outdoors, consider using a fenced
enclosure or runway. |
|
Neuter your cats or prevent them from breeding, and
encourage others to do so. Support or initiate efforts to require licensing and
neutering of pets. In areas where such laws already exist, insist that they be
enforced. For information on local licensing and neutering laws, contact your
local health department or humane society. |
|
Locate bird feeders in sites that do not provide cover for
cats to wait in ambush for birds. Cats are a significant source of mortality
among birds that come to feeders [24]. To prevent cats from climbing to bird
nests, put animal guards around any trees in your yard that may have nesting
birds. |
|
Don't dispose of unwanted cats by releasing them in rural
areas. This practice enlarges rural cat populations and is an inhumane way of
dealing with unwanted cats. Cats suffer in an unfamiliar setting, even if they
are good predators. Contact your local animal welfare organization for help. |
|
Eliminate sources of food, such as garbage or outdoor pet
food dishes, that attract stray cats. |
|
Don't feed stray cats. Feeding strays maintains high
densities of cats that kill and compete with native wildlife populations. Cat
colonies will form around sources of food and grow to the limits of the food
supply. Colonies can grow to include dozens of animals [21]. Maintenance of
colonies of free-ranging or feral cats through supplemental feeding benefits no
one. The cats suffer because of disease and physical injury; native wildlife
suffers from predation and competition, and colonies can be a source of disease
for animals and humans. Those concerned with the welfare of animals can improve
the lives of the many native species that suffer from lack of food and shelter
by protecting and improving the habitats they require [25]. |
Literature cited
[1]
Serpell, S.A. 1988. The domestication of the cat. Pp. 151-158. In: D.C.
Turner and P. Bateson (eds.) The Domestic Cat: The Biology of Its Behaviour.
Cambridge University Press, Cambridge.
[2]
Pet Food Institute. 1982. Pet food information fact sheet. Pet Food
Institute, Washington, D.C.
[3]
Nassar, R. and J. Mosier. 1991. Projections of pet populations from
census demographic data. Journal of the American Veterinary Medicine Association
198: 1157-1159.
[4]
Coleman, J.S. and S.A. Temple. 1993. Rural residents' free-ranging
domestic cats: a survey. Wildlife Society Bulletin 21: 381-390.
[5]
Boddicker, M.L. 1983. House Cats (feral). Pp. C25-C29. In: Prevention and
Control of Wildlife Damage. Institute of Agriculture and Natural Resources,
University of Nebraska, Lincoln, Nebraska.
[6]
Fitzgerald, B.M. 1988. Diet of domestic cats and their impact on prey
populations. Pp.123-147. In: D.C. Turner and P. Bateson (eds.) See [1].
[7]
Bradt, G.W. 1949. Farm cat as predator. Michigan Conservation
18(4):23-25.
[8]
Churcher, P.B. and J.H. Lawton. 1987. Predation by domestic cats in an
English village. Journal of Zoology, London 212:439-455; Eberhard, T. 1954. Food
habits of Pennsylvania house cats. Journal of Wildlife Management 18:284-286;
Fitzgerald, B.M. 1988. See [6].
[9]
Fitzgerald, B.M. 1988. See [6]; Davis, D.E. 1957. The use of food as a
buffer in a predator-prey system. Journal of Mammalogy 38:466-472; Eberhard, T.
1954. See [8]; and Liberg, O. 1984. Food habits and prey impact by feral and
house-based cats in a rural area of southern Sweden. Journal of Mammalogy
65:424-432.
[10]
Coleman, J.S. and S.A. Temple. 1996. On the Prowl. Wisconsin Natural
Resources 20(6):4-8.
[11]
Anni Simpkins, Key West Navel Air Station, personal communication.
[12]
Humphrey, S.R. and D.B. Barbour. 1981. Status and habitat of three
subspecies of Peromyscus polionotus in Florida. Journal of Mammalogy 62:840-844.
[13]
Gore, J.A. and T.L. Schaefer. 1993. Cats, condominiums and conservation
of the Santa Rosa beach mouse. Abstracts of Papers Presented. Annual Meeting of
the Society for Conservation, Tucson, Arizona, June, 1993.
[14]
George, W.G. 1974. Domestic cats as predators and factors in winter
shortages of raptor prey. Wilson Bulletin 86:384-396.
[15]
Erlinge, W., G. Göransson, G. Högstedt, G. Jansson, O. Liberg, J. Loman,
I.N. Nilsson, T. von Schantz and M. Sylvén. 1984. Can vertebrate predators
regulate their prey? American Naturalist 123:125-133.
[16]
Jessup, D.A., K.C. Pettan, L.J. Lowenstine and N.C. Pedersen. 1993.
Feline leukemia virus infection and renal spirochetosis in free-ranging cougar (Felis
concolor). Journal of Zoo and Wildlife Medicine 24:73-79.
[17]
Roelke, M.E., D.J. Forester, E.R. Jacobson, G.V. Kollias, F.W. Scott, M.C.
Barr, J.F. Evermann and E.C. Pirtel. 1993. Seroprevalence of infectious disease
agents in free-ranging Florida panthers (Felis concolor coryi). Journal of
Wildlife Diseases 29:36-49.
[18]
Warfield, M.S. and W.I. Gay. 1986. The cat as a research subject. Pp.
41-54. In: W.I. Gay (ed.) Health Benefits of Animal Research. Foundation for
Biomedical Research, Washington, DC.
[19]
Liberg, O. and M. Sandell. 1988. Spatial organization and reproductive
tactics in the domestic cat and other felids. Pp. 83-98. In: D.C. Turner and P.
Bateson (eds.) See [1]; Natoli, E. and E. de Vito. 1988. The mating system of
feral cats living in a group. Pp. 99-108. In: D.C. Turner and P. Bateson (eds.)
See [1].
[20]
Coleman, J.S. and S.A. Temple. 1993. See [4].
[21]
Natoli, E. and E. de Vito. 1988. See [19].
[22]
Adamec, R.E. 1976. The interaction of hunger and preying in the domestic
cat (Felis catus): an adaptive hierarchy. Behavioral Biology 18:263-272.
[23]
Paton, D.C. 1991. Loss of wildlife to domestic cats. Pp. 64-69. In: C.
Potter (ed.) Proceedings of a Workshop on the Impact of Cats on Native Wildlife.
Endangered Species Unit, Australian National Parks and Wildlife Service, Sydney,
Australia.
[24]
Dunn, E. 1991. Predation at feeders: close encounters of the fatal kind.
Feeder-Watch News 4(1):1-2.
[25]
Bourne, R. (ed.). 1974. Gardening with Wildlife. The National Wildlife
Federation. Washington, D.C. 190 pp.
Additional reading
Jurek, R.M. 1994. A Bibliography of Feral, Stray and
Free-ranging Domestic Cats in Relation to Wildlife Conservation. California
Department of Fish and Game, Wildlife Management Division. 24 pp.
Contacts
Humane Society of the United States, 2100 L Street, NW,
Washington D.C. 20037. Website: http://www.hsus.org
American Bird Conservancy, 1250 24th Street NW, Suite 220,
Washington, DC 20037. Phone: (202) 467-8348
Native Species Network, P.O. Box 405, Bodega Bay, CA 94923.
E-mail: nsn@wco.com
Authors:
John Coleman is a biologist with the Great Lakes Indian
Fish and Wildlife Commission.
Stanley Temple is the Beers-Bascom Professor in
Conservation in the Department of Wildlife Ecology at the University of
Wisconsin-Madison.
Scott Craven is a professor and Extension wildlife
specialist in the Department of Wildlife Ecology at the University of
Wisconsin-Madison.
Special thanks for layout, design and production assistance
to Darrel Covell, wildlife outreach specialist at the University of
Wisconsin-Madison.
Funding:
This publication was made possible by financial support
from the United States Fish and Wildlife Service, National Conservation Training
Center, Division of Education.
Issued in furtherance of Cooperative Extension work, Acts
of May 8 and June 30, 1914, in cooperation with the U.S. Department of
Agriculture, University of Wisconsin-Extension, Cooperative Extension.
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