40 Scientific American, April 2020
SOURCE: “DECREASE IN POPULATION AND INCREASE IN WELFARE OF COMMUNITY CATS IN
A TWENTYTHREE YEAR TRAPNEUTERRETURN PROGRAM IN KEY LARGO, FL: THE ORCATPROGRAM,” BY RACHAEL E. KREISLER ET AL., INFRONTIERS IN VETERINARY SCIENCE;FEBRUARY 1, 2019Graphic by Amanda MontañezOver the past 10 years the science has made it
clear that domestic cats are a conservation nightmare
around the world. Because cats are found at popula-
tion densities 10 to 100 times higher than those of
similarly sized predators, their impact is far more
profound than that of naturally occurring predators
such as raptors, raccoons and snakes. They have been
implicated as a major force in the extinction of 14 per-
cent of bird, mammal and reptile species on islands.
In 2013 Georgetown University conservation biologist
Peter P. Marra and his colleagues at the Smithsonian’s
Migratory Bird Center and the U.S. Fish and Wildlife
Service estimated that feral and outdoor cats kill
about 2.4 billion birds every year—and that is on top
of the estimated 12.3 billion ro dents and other mam-
mals also killed by cats. As free-ranging cats have
been increasingly documented killing endangered
wildlife, disputes such as the one in Key Largo have
popped up around the world. Much less clear, howev-
er, is how to tackle the problem.
Historically, “cat control” meant rounding up and
killing strays every now and then, often as a reaction-
ary measure when things got out of hand. But given
a cat’s extra ordinary fertility rate, it did not take long
for the feline population to get right back to where it
started. Over the past few decades governments have
tried an arsenal of more deliberate strategies, includ-
ing poison sausages, sharpshooters, deadly virusesand a toxic gel sprayed on cats’ fur. Few of these tac-
tics were practiced consistently over a long-enough
period. Nearly all of them have failed, emboldening
people who work in animal welfare to insist that sim-
ply killing cats is not just cruel but ineffective: today
there are anywhere from 70 million to 100 million
feral or unowned cats in the U.S. alone.
Instead cat supporters advocate for humanely
trapping cats, sterilizing them and returning them
to their colonies, or social groups, in the wild—a pro-
cess known as trap-neuter-return, or TNR. If free-
ranging cats are prevented from reproducing, feral
cat colonies will naturally decrease in size over time
as cats die. In the mid-1980s Julie Levy, who was
then a veterinary student at the University of Cali-
fornia, Davis, led one of the country’s first TNR
efforts. Within a few years almost all the campus’s
feral cats had been trapped and sterilized, and by
the time Levy graduated the area around the veteri-
nary school was nearly cat-free. “People were so
excited to have an alternative solution,” she recalls.
In 1993 word of Levy’s California TNR project
reached Alan Litman, a prolific inventor and a resi-
dent of the Ocean Reef Club. At the time thousands
of feral cats roamed the property, which takes up
one third of Key Largo. The occasional roundups for
euthanasia, which did not sit well with many locals,
were not working. Cat feces were everywhere, andA Successful Cat Decline
Advocates of trap-neuter-return (TNR) argue that it is the only effective
method to reduce a free-roaming cat population. But few TNR efforts
have data to prove it works, particularly in a restricted location and
over a long enough period. In Florida’s Key Largo, the Ocean Reef
Club TNR (ORCAT) program is one exception, with more than 20
years of data. A retrospective analysis, published in 2019 in Frontiers
in Veterinary Science, shows that the feral cat population did decline—
but not because of TNR alone. Other methods of cat control
were incorporated, such as adopting out friendlier cats
and euthanizing sick ones. In 2016 ORCAT began
permanently containing some cats in
a new enclosure rather than
returning them to the wild.5001001502002503003504004505005506006507001995 2000 2005 2010 2015Estimates based on
medical records (pink)Estimates based on
cat census data (blue)Estimated Population of Free-Roaming CatsCensuses were performed at irregular
intervals from June 1999 to February 2013.
For each survey, feeding stations were
set up around the Ocean Reef Community,
and a caretaker counted the number
of cats at each station.To track the effects of the TNR program,
researchers reviewed paper-based medical
records for cats who first visited the
ORCAT clinic from April 1995 through
December 2017.In 2012 and 2013 trapping efforts decreased
after a change in leadership at the Grayvik
Animal Care Center. As a result, the cat
population rose during those two years.© 2020 Scientific American