Download A Reconsideration of Trap-Neuter-Vaccinate

Feral Cat Problems:
A Reconsideration of Trap-Neuter-Vaccinate-Return
and
An Alternative Approach
Gerald R. Rising
SUNY Distinguished Teaching Professor Emeritus
University at Buffalo
After dark
all cats are leopards.
— Native American Proverb
Abstract
Cat TNVR (Trap-Neuter-Vaccinate-Return) is widely proposed as a response to problems
with feral cats. Unfortunately the R of that acronym, returning the cats into the environment from
which they were trapped, creates serious problems: feral cat communities are established where
cats are fed and protected by volunteers but otherwise continue to range free. Research shows
many negative results of this: (1) these cats continue to kill birds and mammals at an alarming
rate; (2) the process not only does not, as widely claimed, reduce the number of feral cats but
instead often increases their population; (3) availability of the colonies encourages abandonment
of additional house pets; (4) despite vaccination there are human and wildlife health risks
associated with feral cats; and (5) the process is very expensive and, because the cat population
is not reduced, these costs do not decline over time. A proposal for the removal of feral cats from
the environment through containment is offered as an alternative.
Introduction
Based on their 2009 review of 65 documents, most of them peer-reviewed research papers,
(Dauphine & Cooper, 2009) summarize: "American birds face an estimated 117 to 157 million
exotic predators in the form of free-ranging domestic cats (Felis catus), which are estimated to
kill at least one billion birds every year in the United States.1 Cats have contributed to declines
and extinctions of birds worldwide and are one of the most important drivers of global bird
extinctions. Studies have shown that cats pose threats to many bird populations, including
priority species for conservation, through their predation of adult, nestling, and juvenile birds.
Cats also have impacts on birds through competition with native predators such as raptors, and
through the harboring and transmission of zoonotic and other diseases to birds and other wildlife.
In addition to direct mortality, cats also cause stress responses in birds due to predation risk that
may result in further bird population declines."
It is easy to think that concerns about declines and extinctions are problems elsewhere, but
consider the conjectured effect of two feral cats that were abandoned on Goat Island above
Niagara Falls in about 2005. Their introduction was soon followed by the loss of the small fox
1
A later study published in 2013 in Nature Communications estimated that cats kill up to 3.7 billion birds and
between 6.9 billion to 20.7 billion mammals in the continental U.S. each year. To place those numbers in a local
context, they represent an average of over 6000 birds and 18000 mammals killed by cats in each of the over 3000
U.S. counties per day.
squirrel colony on that island. While cause-and-effect is not established for this coincidence, it
speaks to the fact that we too have small and sensitive populations of individual species that can
be affected by the introduction of an alien to which they have not developed adequate defense
mechanisms.
Supported Cats Continue to Kill Birds and Mammals
In the past bird and terrestrial animal depredation by free-roaming cats (pets allowed to run
free as well as feral cats) were often estimated from the number of captures returned to the home
by house pets. A study by (Loyd, Hernandez, Carroll, Abernathy, & Marshall, 2013) had pet
owners attach video cameras to their cats before allowing them to range free. They then recorded
the length of time on their own and the number of returned prey. This study demonstrated that a
substantial proportion of free-roaming cats kill prey despite being fed at home. Moreover, it
showed clearly that returned prey far underestimates the number of animals killed by cats as less
than a quarter were returned.
It is interesting to extrapolate the results of this study of 55 cats in Athens-Clarke County,
which the authors describe as a "unified city-county area of northeastern Georgia." Considering
only the owned free-roaming cats of that county, estimated from Humane Society data to be
13,500 animals, in less than ten days their data would extrapolate to almost 10,000 birds and
terrestrial animals killed. (That number does not even include the prey of feral cats.)
(Winter, 2004), (Winter & Wallace, 2006), (Castillo & Clarke, 2003), (Lepczyk, Mertig, &
Liu, 2003) and (Loss, Will, & Marra, 2013) offer additional examples of the effect of cat
predation on wildlife communities and indict TNVR for its failure to respond to these problems.
(Jessup, 2004) lists the bird species among the 1015 cat kills turned in to a single wildlife
education center over a ten month period. (Bonnington, Gaston, & Evans, 2013) go further to
blame free-roaming cats for indirect negative effects: by frightening the birds and preventing
them from feeding their young, for example, they reduced nestling growth rates by 40%. Also
birds' defensive activities related to cats called the attention of crows that subsequently raided
nests.
The Effect of TNVR on the Population of Feral Cats
It is important to understand that the domestic cat (Felis catus) is a species alien to the entire
Western Hemisphere.2 Released into our ecosystem it presents problems similar to all introduced
species. Resident prey populations have no defense against it and resident carnivores are
unfamiliar with it as a prey target. These advantages offer the opportunity for exponential
population growth.
In an isolated setting this population growth would be expected to reach a limit controlled by
competition for food and the effects of disease and accidents. TNVR takes away the most
important aspect of this limit by providing food at feral cat colony sites. TNVR also substantially
increases the lifetime of the supported cats.
Despite this, TNVR proponents claim that their approach is better than euthanasia because
trapped cats are neutered and cannot breed. They cite a study in Tasmania (Lazenby, Mooney, &
Dickman, 2014) that showed a substantial increase in the local cat population after a program of
The native cats of the United states – cougar (Puma concolor), bobcat (Lynx rufous) and lynx (Lynx canadensis) –
are not in the same genus.
2
euthanasia was implemented. In fact the culling reported in that study involved only 26 cats over
a period of 13 months in a large parkland region. The title of the study, in fact, includes "lowlevel culling." In no way does this study indicate that TNVR would do better. What it does
suggest instead is the necessity for removal of all feral cats.
In another study that is generally favorable to TNR (Foley, Foley, Levy, & Paik, 2005) the
researchers found "no indications of a significant reduction in per capita growth rate. (In other
words the populations of the two California counties they studied continued their exponential
feral cat population growth.)
Other studies are far less supportive of TNR programs. For example, (Lohr, Cox, & Lepczyk,
2012) modeled the effects of TNR3 and TE (trap and euthanize) on the island of Oahu, Hawaii.
Their analysis showed no reduction in the population of TNR cats over a 30-year period when
taking into account minimal (10%) immigration.
Cat Abandonment
It should be recognized that the feral cat problems of urban and suburban areas have been
largely created by the abandonment of pet house cats and their kittens,4 an activity that continues
unabated and is rarely punished today. Studies that model the effects of TNVR usually do not
take this into account or, if they do, they assume a low level of such dumping.
To show just how fast such additions to the feral cat population compromise control attempts
(Lohr et al., 2012) showed that just 10% of an original population added through this means each
year would completely replace that completely eliminated (zero) population in just six years.
(Lee et al., 2014) modeled TNR programs in Knox County, Tennessee, finding that with "a
high level of immigration and a low rate of abandonment, a 74% spay rate would be necessary
just to stabilize the local population. Even with this restriction of the rate of abandonment, this is
a rate of neutering that is rarely achieved by TNR advocates.
Health Concerns
In the first four months of 2015, 83 cases of rabies were confirmed in New York State: 3 of
those cases were cats, none were dogs. Veterinary Dr. Paul Barrows comments, in (Barrows,
2004) on this health issue: "Despite cats being the most frequently reported rabid domestic
animal in the United States, proponents of TNR rarely address the fatal nature of untreated
human rabies infections, nor do they readily acknowledge that nearly all TNR colonies contain
unvaccinated cats or previously immunized cats whose immunity against rabies is diminished or
has disappeared," and he cites a case in New Hampshire where "exposures to a kitten of
unknown origin that was subsequently diagnosed with rabies led to the treatment of an estimated
665 individuals and expenses of more than $1.5 million for investigation, laboratory testing, and
rabies immunoglobulin and vaccines." Barrows also cites park closures in Florida due to rabies
diagnoses in feral cats and he summarizes: "Rabies risks are real."
An analysis of concerns related to cat rabies by (Roebling et al., 2013) confirms this and they
recommend, "Appropriate animal control laws including removal of stray or unwanted cats
3
When health effects are not considered, TNVR programs are often shortened to the older acronym TNR in the
literature.
4
In the past and in many rural communities today unwanted kittens were destroyed. Too often today their owners
are unwilling to do this but are willing instead to assign them a life to which they are ill prepared.
should be enforced rather than relying on indirect population management strategies (e.g. trapneuter-vaccinate-release programs) in order to control feral cat populations and reduce the risk of
zoonotic diseases such as rabies."
A review of various cat-borne diseases is in (Gerhold & Jessup, 2013). In addition to rabies
they list "toxoplasmosis, cutaneous larval migrans because of various nematode parasites,
plague, tularemia and murine typhus." In summary, they state: "While citizens who are
concerned about the perceived improved welfare of cats in TNR programs may be very vocal in
their support of free-roaming cat populations, local, county and state legislative and medical
officials need to understand the economic and public health threats associated with free-roaming
cat populations." Ill cats defecating on playgrounds represents a particular hazard.
Clearly the V for vaccination in TNVR addresses some of these problems, but vaccinations
have time limits (one to three years for rabies, for example) and supported feral cats often live
beyond these limits. (Gunther, Finkler, & Terkel, 2011) suggest that a spayed cat may live two or
three times as long as an intact cat due to fewer deaths related to trauma and disease. Also
vaccination (and worming) does not prevent later infections picked up from the environment.
Costs Associated with TNVR
It is difficult to determine the costs associated with TNVR because of the extensive use of
volunteers and the contributions of supporters. An indication that those costs are substantial,
however, is suggested by the five-year budget of the Maddie's Spay/Neuter Project in Erie
County, NY of $6,028,694.
A Summary of TNR Claims as Seen by Scientists
In their summary of the scientific literature related to TNR (Longcore, Rich, & Sullivan, 2009)
address the claims of TNR supporters: "We compared the arguments put forth in support of TNR
by many feral cat advocates with the scientific literature. Advocates promoting TNR often claim
that feral cats harm wildlife only on islands and not on continents; fill a natural niche; do not
contribute to the decline of native species; and are insignificant vectors of disease. Advocates
also frequently make claims about the effectiveness of TNR, including claims that colonies of
feral cats are eventually eliminated by TNR and that managed colonies resist invasion by other
cats. The scientific literature contradicts each of these claims. TNR of feral cats is primarily
viewed and regulated as an animal welfare issue, but it should be seen as an environmental issue,
and decisions to implement it should receive formal environmental assessment."
A Better Approach
If TNVR is the wrong approach to the problem of feral cats, doing nothing is certainly no
better. We have today a national problem with an alien species that, because it is not being
addressed in satisfactory ways, is getting worse. I outline here a series of actions that, if
implemented, could begin to address this problem:
1. Continue and expand the current trap-neuter-vaccinate (TNV) programs of TNVR, but replace
the R for return in TNVR with R for remove. All urban and suburban feral cats should be
removed from our environment. Only cats associated with farm buildings or other specifically
designated locations would be exempt from this.
2. Replace the current free-roaming cat colonies with containment facilities for these cats.
3. Continue to encourage adoption of trapped cats for house pets with the stipulation that the cat
will be kept indoors.
4. Only in cases of diseased cats and those that are able to avoid capture should euthanasia be the
response.
5. Increase the crime of cat abandonment from misdemeanor to felony and establish a severe
fiscal penalty for this crime.
6. Make allowing a pet cat to roam unleashed outside the owner's yard a misdemeanor subject to
a fiscal penalty.
7. Require all urban and suburban cats to be licensed with an annual fee designated specifically
to cover the costs of the capture and containment programs. Justify this fee by making it clear
to cat owners and other cat lovers that it is to prevent the euthanasia for feral cats.
8. Introduce a public educational program with a special focus on elementary schools that
strongly encourages keeping pet cats indoors and having pet cats neutered.
The major change in this proposed program is the replacement of the current free-roaming cat
colonies with contained colonies. While there are obvious expenses associated with this change,
some of those expenses and the associated necessary care are already being provided by
volunteers with community support. The real cost resides in the construction of the
containments.
These containment facilities should be designed to allow the confined cats as much room as
possible up to an acre or more. They should provide food, water, shelter and insofar as possible a
natural environment. But they should be carefully designed so that the cats cannot escape. Secure
fencing is a necessity.
Note that there is an important aspect to this program: unlike TNR programs that are never
ending, this program should reduce over time. While a few cats would immigrate from the
countryside, according to a Department of Environmental Conservation officer, they are far less
common there. Continuing capture of feral cats should, however, be continued.
Statements from Organizations Opposed to TNVR
Here is a selection of policy resolutions and statements from some of the national groups
opposed to the support of free-roaming feral cat communities:
American Association of Wildlife Veterinarians: "support actions...to ban or eliminate feral cat
colonies."
American Ornithologists Union: "strongly opposes programs to maintain feral cat communities."
National Association of State Public Health Veterinarians: "is concerned that managed cat
colonies may foster irresponsible cat ownership and will promote the free-roaming of owned
cats."
American Bird Conservancy: "TNR is not a practice that should be officially sanctioned by any
local government. Studies have repeatedly shown that TNR does not work in reducing the
number of feral cats. Instead, well-meaning but misguided volunteers perpetuate the problem
and contribute to millions of bird deaths. TNR is simply not the solution."
People for the Ethical Treatment of Animals (PETA): "Sadly, our experience with trap, spay-andneuter, and release programs and “managed” feral cat colonies has led us to question whether
or not these programs are truly in the cats’ best interests. We receive countless reports of
incidents in which cats—'managed' or not—suffer and die horrible deaths because they must
fend for themselves outdoors. Having witnessed firsthand the gruesome things that can
happen to feral cats, we cannot in good conscience advocate trapping and releasing as a
humane way to deal with overpopulation."
Committee on Environmental Issues of the American Veterinarian Medical Association:
"strongly supports and encourages humane elimination of feral cat communities." (Barrows,
2004)
The publication (Winter, 2010) lists additional opponents of TNVR.
A Personal Note
It is important that I point out that, despite my opposition to free-ranging feral cat
communities, I bear no animosity to house cats. In fact I consider them attractive and interesting
pets and I particularly admire their independence. On the other hand I am deeply sensitive to the
problems associated with both feral cats and pet cats that are being supported as they decimate
our wildlife populations.
Literature Cited
Barrows, P. L. (2004). Professional, Ethical, and Legal Dilemmas of Trap-Neuter-Release.
Journal of the American Veterinary Medical Association, 225(9), 136-1369.
Bonnington, C., Gaston, K. J., & Evans, K. L. (2013). Fearing the Feline: Domestic Cats Reduce
Avian Fecundity through Trait-Mediated Indirect Effects that Increase Nest Predation by
Other Species. Journal of Applied Ecology, 50, 15-24.
Castillo, D., & Clarke, A. L. (2003). Trap/Neuter/Release Methods Ineffective in Controlling
Domestic Cat "Colonies" on Public Lands. Natural Area Journal, 23(3), 247-253.
Dauphine, N., & Cooper, R. J. (2009). Impacts of Free-Ranging Domestic Cats (Felis catus) on
Birds in the United States: A Review of Recent Research with Conservation and
Management Recommendations. Paper presented at the The Fourth International Partners
in Flight Conference: Tundra to Tropics, McAllen, TX.
Foley, P., Foley, J. E., Levy, J. K., & Paik, T. (2005). Analysis of the Impact of Trap-NeuterReturn Programs on Populations of Feral Cats. Journal of the American Veterinary
Medical Association, 227(11), 1775-1781.
Gerhold, R. W., & Jessup, D. A. (2013). Zoonotic Diseases Associated with Free-Roaming Cats.
Zoonoses Public Health, 60(3), 189-195.
Gunther, I., Finkler, H., & Terkel, J. (2011). Demographic Differences between Urban Feeding
Groups of Neutered and Sexually Intact Free-Roaming Cats Following a Trap-NeuterReturn Procedure. Journal of the American Veterinary Medical Association, 238, 11341140.
Jessup, D. A. (2004). The Welfare of Feral Cats and Wildlife. Journal of the American
Veterinary Medical Association, 225(9), 1377-1383.
Lazenby, B. T., Mooney, N. J., & Dickman, C. R. (2014). Effects of Low-Level Culling of Feral
Cats in Open Plantations: A Case Study from the Forests of Southern Tasmania. Wildlife
Research, 41, 407-420.
Lee, L. E., Robl, N., Bugman, A. M., Nguyen, A. T. N., Lammers, B., Fisher, T. L., . . . New, J.
C. J. (2014). Modeling Feral Cat Population Dynamics in Knox County, TN. University
of Tennessee.
Lepczyk, C. A., Mertig, A. G., & Liu, J. (2003). Landowners and Cat Predation across Rural-toUrban Landscapes. Biological Conservation, 115, 191-201.
Lohr, C. A., Cox, L. J., & Lepczyk, C. A. (2012). Costs and Benefits of Trap-Neuter-Release and
Euthanasia for Removal of Urban Cats in Oahu, Hawaii. Conservation Biology, 27(1),
64-73.
Longcore, T., Rich, C., & Sullivan, L. (2009). Critical Assessment of Claims Regarding
Management of Feral Cats by Trap-Neuter-Return. Conservation Biology, 23(4), 887894.
Loss, S. R., Will, T., & Marra, P. P. (2013). The Impact of Free-Ranging Domestic Cats on
Wildlife in the United States. Nature Communications, 4, 1-7.
Loyd, K. A., Hernandez, S. M., Carroll, J. P., Abernathy, K. J., & Marshall, G. J. (2013).
Quantifying Free-Roaming Domestic Cat Predation Using Animal-Borne Video
Cameras. Biological Conservation, 160, 183-189.
Roebling, A. D., Johnson, D., Blanton, J. D., Levin, M., Slate, D., Fenwick, G., & Rupprecht, C.
E. (2013). Rabies Prevention and Management of Cats in the Context of Trap-NeuterVaccinate-Release Programmes. Zoonoses and Public Health, 61(4), 290-296.
Winter, L. (2004). Trap-Neuter-Release Programs: The Reality and the Impacts. Journal of the
American Veterinary Medical Association, 225(9), 1369-1376.
Winter, L. (2010). 'Managed' Cat Colonies: The Wrong Solution to a Tragic Problem. from
http://www.abcbirds.org/abcprograms/policy/cats/materials/colonies.pdf
Winter, L., & Wallace, G. E. (2006). Impacts of Feral and Free-Ranging Cats on Bird Species of
Conservation Concern: A Five State Review of New York, New Jersey, Florida,
California, and Hawaii (pp. 1-28): American Bird Conservancy.