Prepared by: Bryan Kortis, Executive Director, Neighborhood Cats
September 5, 2007
Trap-Neuter-Return (TNR) as a Proposed Approach
To Reducing the Feral Cat Population at JFK Airport
Introduction
Since Neighborhood Cats began working with feral cats in New York City in
1999, there have been continual reports of feral cat colonies in and around JFK Airport
and it is likely substantial numbers of cats have been present on airport grounds for
considerably longer. To date, no systematic or effective approach has been undertaken
to significantly reduce the feral cat population at JFK. Instead, it appears a reactive,
anecdotal approach has been pursued wherein individual colonies of cats have been
trapped and removed from particular locations in response to complaints or other
nuisance-related concerns. This is typical of traditional animal control methodology in
regards to feral cats and has achieved typical results – a lowering of the number of cats at
particular locations (sometimes only temporarily), but having little to no effect on the
overall problem.
It should be noted that the impact of feral cats can touch not only on animal
welfare concerns, but also public health (i.e., rabies) and wildlife (predation). These
additional concerns emphasize the need for an effective program that will substantially
lower the feral cat population on a permanent basis.
Why Traditional Approaches Fail – Trap & Remove
Efforts to eradicate feral cats through trap and remove efforts fail to achieve
global reduction of the feral population for a number of reasons, including (a) the
“vacuum effect,” (b) increased survival rates by untrapped cats, (c) abandonment of
domestic cats and, (d) lack of animal control resources. All of these factors are at play in
an area the size of JFK Airport.
The Vacuum Effect
The “vacuum effect” was first chronicled by wildlife biologist Roger Tabor during his
studies of London street cats. He observed that when a colony of feral cats was suddenly
removed in toto from its territory, cats from neighboring colonies soon moved in and
began the unchecked cycle of reproduction anew until the population was back up to its
former level.1 As explained in another study, “the presence of feral cats in a place
indicates an ecologic niche for approximately that number of cats; the permanent removal
of cats from a niche will create a vacuum that then will be filled through migration from
outside or through reproduction within the colony, by an influx of a similar number of
feral cats that are usually sexually intact; and removal of cats from an established feral
1
Tabor, Roger, “The Wild Life of the Domestic Cat,” p. 183 (1983).
colony increases the population turnover, but does not decrease the number of cats in the
colony.”2
Migration of new cats into recently vacated territory can be traced to two factors:
first, feral cats are present at a particular location for a reason - the habitat provides
adequate food and shelter. Second, no feral colony is an island, but is part of an
extensive ecosystem containing similar colonies, one adjoining the next. As a result, if a
colony is removed from its territory, but the habitat is left unchanged, neighboring cats
will move right in to take advantage of the food source and shelter that remains.
Reproduction and population growth ensue until the natural ceiling is again reached, that
being the number of cats the habitat can support.3
Eliminating all food sources is virtually impossible.4 Once a cat is spotted by a
concerned individual who starts to leave food, a food source is created. It is also difficult
in institutional settings, such as a large airport, to adequately seal dumpsters and other
garbage containers to keep out feral cats.
Increased Survival Rates of Untrapped Cats
The trapping and removal of every member of a feral colony is a difficult and timeconsuming task. When busy animal control personnel attempt to trap a feral colony,
inevitably some cats are left behind. With less competition for the food and shelter that
remains, more of the offspring of the remaining cats survive than before the trapping until
the carrying capacity of the habitat is again reached.5
Abandonment
Unaltered pet cats are constantly being abandoned at JFK Airport. Without monitors
and caretakers in place to quickly capture and either fix or adopt out these former pets,
they too, are available to repopulate any suitable habitat made vacant by trap-and-remove
efforts.
Lack of animal control resources
It is unlikely JFK Airport will ever be able to devote the amount of personnel
required to trap and remove enough feral cats fast enough to impact the size of the overall
cat population.
Waukegan, Illinois: a case study in the failure of trap-and-remove
Waukegan, Illinois is a township of 88,000 located on the shore of Lake Michigan.
Waukegan's long-standing method for controlling their feral cat population has been the
traditional trap-and-remove.6 A few years ago, the town made news by trying to
Zaunbrecher, Karl I., DVM, & Smith, Richard E., DVM, MPH, “Neutering of Feral Cats as an Alternative
to Eradication Programs,” Journal of the American Veterinary Medical Association, Volume 203, Number
3, August 1, 1993.
3
Clifton, Merritt, “Seeking the truth about feral cats and the people who help them,” ANIMAL PEOPLE,
Nov. 1992.
4
Hartwell, Sarah, “Why Feral Eradication Won’t Work,” (1994, 2003),
www.messybeast.com/eradicat.htm.
5
Clifton, Merritt, “Street Dog & Feral Cat Sterilization and Vaccination Efforts Must Get 70% or Flunk,”
ANIMAL PEOPLE, October 2002.
6
Hamill, Sean, “Neuter, release program for feral cats stirs debate,” Chicago Tribune, July 7, 2004.
2
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effectively ban TNR. The town’s council enacted an ordinance that forbids the release of
any cat except into an outdoor enclosure. To build and operate such an enclosure, a
kennel license must be sought and paid for. In addition, a prior ban against feeding stray
cats is in effect. Stiff fines enforce these provisions.7
According to Tina Fragassi, the local animal control warden, her agency had trapped
and removed approximately 500 feral cats each of the past eleven years. 8 In Ms.
Fragassi's view, this steady number reflected the success of Waukegan's policies in
controlling the cats.9 The truth is just the opposite and points to the futility of trap-andremove.
That every year 500 cats need to be trapped indicates the feral population is
remaining at the same level. The feline faces may be changing, but the total number of
cats is staying the same. By contrast, a successful animal control approach would mean
fewer and fewer feral cats in the community as reflected by continually falling seizures
and complaints. This is the goal of TNR. As explained by Dr. Margaret Slater, DVM, a
leading feral cat academic, TNR “should be considered an interim solution to the problem
of feral, free-roaming cats – the first step towards reducing the size of the colony through
attrition.”10
Eradication of feral cats has proven successful only on small, uninhabited islands
after many years of intensive control measures such as poisoning, hunting, trapping and
introduction of infectious feline diseases.11 One of the best-known examples of the
difficulty of eradication is Marion Island, a small uninhabited island (12 miles x 8 miles)
located southeast of South Africa between South Africa and Antarctica.12
In 1949, a group of scientists left the island, leaving behind 5 unneutered cats. By
1977, there were an estimated 3,400 cats preying on ground-nesting seabirds.13
Deliberate infection of the feral cat population with Feline Panleukopenia Virus (feline
enteritis) followed and killed around 65% of the cat population by the early 1980’s.14
Many of the remaining 35% developed immunity to the disease and continued to breed.15
Between 1986 and 1989, 897 cats were further exterminated by hunting. Traps with
poison baits were then used to kill the cats who eluded the guns. No cats have been seen
since 1991. In 1993, sixteen years after it was begun, the eradication program was
declared a success.16
The methods used on Marion Island – introduction of infectious disease, shooting and
poisoning – would be unfeasible in a populated area such as JFK Airport for safety, cost
and aesthetic reasons.17 Even assuming such techniques could be employed, the vacuum
7
Ibid.
Hamill, Sean, Chicago Tribune reporter, interview of Tina Fragassi, July 2004.
9
Ibid.
10
Slater, Margaret R., DVM, Community Approaches to Feral Cats, p. 14 (Humane Society of US Press,
2002) [hereinafter referred to as “Slater”].
11
Levy, Julie, DVM, “Feral Cat Management,” Chap. 23, p. 380, in Shelter Medicine for Veterinarians and
Staff (Blackwell Publishers, 2004) [hereinafter referred to as “Levy”].
12
Hartwell, Sarah, “Why Feral Cat Eradication Won’t Work,” (1994, 2003),
www.messybeast.com/eradicat.htm.
13
Ibid.
14
Id.; Berkeley, Ellen Perry, Maverick Cats, pp. 123-124 (New England Press, 1982, 2001).
15
Hartwell (see fn. 71, supra).
16
Ibid.
17
Levy, p. 381.
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effect and abandonment of new cats, factors not present in a geographically isolated
situation like Marion Island, would likely outpace eradication efforts.
Why Traditional Approaches Fail – Feeding Bans
Feeding bans have also often been attempted as a solution to a community’s feral
cat overpopulation problem. To date, although feeding bans have been enacted over the
years in municipalities throughout the United States, there is not yet a single documented
case of a ban having lowered the feral cat population of a community the size of JFK
Airport. Feeding bans fail for two basic reasons: first, the cats don’t go away. They are
very territorial and quite adept at finding new food sources, plus they can survive for
weeks without solid food and continue to reproduce. Second, bans are unenforceable and
people who care for the cats almost always disobey them despite the threatened loss of
funds, jobs or liberty.
Trap-Neuter-Return’s Demonstrated Success
Trap-Neuter-Return (TNR) involves trapping the cats in a colony, having them
neutered and vaccinated for rabies, then returning the ones that cannot be adopted to their
original territory. Once returned, a caretaker provides the cats with food and shelter, and
monitors the colony for newcomers. TNR is endorsed by The Humane Society of the
United States, American Society for the Prevention of Cruelty to Animals (ASPCA),
Humane Society of New York and Mayor’s Alliance for NYC’s Animals. It works
where traditional methods fail because it engages a large volunteer base, eliminates
reproduction through sterilization, and sets up a long-term monitoring system for new
cats which can protect and further progress in reducing the numbers.
Trap-Neuter-Return as a method of feral cat population reduction cannot
reasonably be dismissed as only a theoretical possibility. There are now numerous
documented examples of its success. Dr. Julie Levy, DVM, conducted an eleven year
TNR project at the University of Florida, Gainesville.18 The program resulted in an 85%
decline in the feral population over the course of the study from 155 cats on campus in
1991 to 23 in 2002. Dr. Levy concluded that, "A comprehensive long-term program of
neutering followed by adoption or return to the resident colony can result in reduction of
free-roaming cat populations in urban areas."
An excellent example of how TNR reduces numbers through both adoption and
sterilization is provided by the TNR program practiced with municipal approval and
cooperation in Newburyport, a coastal town in Massachusetts. In 1992, after attempts to
eradicate the approximately 300 cats living on the town’s waterfront had failed, the
municipality agreed to allow a TNR project. In 1992 through 1993, a private
organization, Merrimack River Feline Rescue Society trapped 200 of the cats, adopting
out 100 of them and returning the rest.19 By 1998, 100 percent of the feral population had
Levy, J.,“Evaluation of the effect of a long-term trap-neuter-return and adoption program on a freeroaming cat population,” Journal of the American Veterinary Medical Association, Vol. 222, No. 1,
January 1, 2003.
19
Interview, Stacey LeBaron, President, Merrimack River Feline Rescue Society, January 2007.
18
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been sterilized. Presently in 2007, the feral population has almost completely
disappeared with only five or six cats remaining.20
Here in New York City, the colony on the Upper West Side of Manhattan which
launched the now city-wide TNR effort is now extinct, the original colony having
numbered 32 cats in 1999. In Riverside Park, also on the Upper West Side, TNR efforts
begun in the fall of 2001 have seen approximately 65 cats in five colonies fall to
approximately 25 cats in five colonies. This is a particularly noteworthy example
because, like JFK Airport, there is extensive abandonment of cats in the park Without
feral cat caretakers constantly monitoring for dumped cats, population reduction would
not have been possible. At the Fresh Kills Landfill in Staten Island, TNR has reduced
what was a population of 45 cats in 2003 to fewer than 20 today. On Rikers Island, 300
cats spread out over 20 colonies have been lowered to half that number over the past five
years by using TNR. Rikers is another example of a situation prone to abandonment due
to the thousands of employees commuting on and off the island on a daily basis. The
entire Upper West Side of Manhattan, according to statistics provided by Animal Care &
Control, saw a 73 percent drop in the number of stray and feral cats entering city shelters
after two and a half years of intensive TNR work.
Conclusion
If properly implemented, TNR can achieve similar results at JFK Airport in terms
of lowering numbers. In addition, a comprehensive cat management plan has other
advantages. In locations identified as unsuitable for the cats, whether for reasons of
animal welfare or wildlife predation, relocation to acceptable areas would be possible. In
addition, all parties concerned with the cats, including feeders, airport officials and the
public, would be working together instead of in opposition.
Once the feral population was sterilized to a significant extent, then attention
could be paid to addressing the sources of the ferals. Combining a sterilized feral
population with a reduced inflow of cats could lead as close as possible to the elimination
of the free-roaming cat population at JFK Airport.
On the other hand, if TNR is rejected, only failed methods remain as tools and it
is highly unlikely any real overall progress on this issue will be achieved.
20
Ibid.
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