April 2020, ScientificAmerican.com 41owners filed a never-ending stream of complaints
about the noise of cat fights and the smell of territory
markings. Litman lobbied Ocean Reef to try TNR,
and the club agreed, providing long-term funding to
launch ORCAT with money from the homeowners’
association and private donations. Litman hired
Susan Hershey, a technician at a local veterinary hos-
pital, to head up the program. When she arrived in
1995, Hershey popped open a can of food on the
street and encountered “70 or 80 cats, easily,” she
recalls. “It was an extreme problem.”
Hershey spent most of the daylight hours baiting
traps with cans of Friskies and waiting for unsus-
pecting cats to step inside. As the cats learned her
routine and began to avoid the traps, Hershey con-
stantly evolved her methods. Many of the cats she
trapped were sick and had to be humanely eutha-
nized; others were friendly and could be adopted
into homes. Hundreds of cats, however, were healthy
enough to be spayed or neutered but too fearful of
humans for a life indoors. These cats were returned
to their colonies with the top of their left ear removed
to indicate that they were fixed. For five years Her-
shey and a growing team trapped and neutered prac-
tically around the clock. Slowly but surely, the num-
ber of cats at Ocean Reef began to drop.
THE NEGOTIATOR
news of oRcat’s success began to spread throughout
the animal welfare community. Hershey became
something of a TNR celebrity, fielding visitors from
around the world who wanted to learn how to repli-
cate the Key Largo program. The area’s feral cats
also attracted biologist Michael Cove, then a young
doctoral student at North Carolina State University,
who arrived at the Crocodile Lake National Wildlife
Refuge in 2012. Although the number of cats at
Ocean Reef had indeed declined, the woodrats were
still in serious trouble, and Cove wanted to figure
out how to better protect them. Feral cats often wan-
dered into the refuge, lured by the industrious activ-
ities of the woodrats. Cove wanted to document the
effects of cats on the woodrat population and under-
stand how the cats—among other factors—limited
woodrat recovery. To conservationists, the presence
of ORCAT was anything but a victory.
Although a handful of studies from Rome to Rio
de Janeiro have indeed shown persistent population
reductions from TNR, it is not easy to sterilize enough
cats to create a steady downward population trend,
explains conservation biologist Grant Sizemore of
the American Bird Conservancy. Modeling studies
have shown that upward of 90 percent of the cats
need to be fixed to create a steady population decline,
and trapping that many cats is nearly impossible.
Domestic cats reproduce so efficiently that even
small gaps in cat colony maintenance can lead to a
resurgence in numbers—something ORCAT’s own
data show. Additionally, the presence of cared-for
feral cats has been found to encourage people to
dump their unwanted cats in the same area—which
is often a reason the strategy fails. (It also helps to
explain the success of ORCAT, which is located in a
gated community on a small island.) “TNR is a Band-
Aid solution for a gaping wound,” Sizemore says.
TNR supporters acknowledge that the method is
imperfect. But Levy and Hershey argue that even with
all its flaws, TNR is the only technique that has so far
been shown to reduce cat populations over time. Hu -
mans have been killing cats for centuries, Levy says,
yet millions of feral cats are currently living in the U.S.
Marra disputes this logic, arguing that there is a dif-
ference between the occasional roundups of problem
cats and newer efforts to strategically wipe cats out
of an ecosystem. Modeling studies by Auburn Univer-
sity ecologist Christopher Lepczyk and others seem to
support Marra’s point: under most circumstances,
TNR is less effective at reducing cat populations than
euthanizing the cats once they are trapped.
Both sides have accused the other of cherry-pick-
ing data to support its points. In 2018 Marra and
other conservationists wrote an article calling TNR
promoters “merchants of doubt,” the same term used
for those who defend tobacco products and deny cli-
mate change for personal gain. But the underlying
issue is that there are few data to start with, both on
the scope of the problem (feral cats are difficult to
count accurately, for instance) and on the best meth-
ods to reduce cat numbers in the context of bolster-
ing wildlife. In that sense, the conservation cat fight
has rested more on opinions than on evidence-based
science. In a May 2019 article entitled “A Moral Panic
over Cats” in Conservation Biology, ethicists, anthro-
pologists and conservation biologists argued for see-
ing the gray areas.
Stepping into the morass, Cove knew that expel-
ling cats from the refuge would require buy-in from
ORCAT. He needed to show Hershey evidence that
her cats were guilty as charged. No one had done
fine-grained studies showing precisely how cats
affected any species of endangered rodent, so that
was where he started. Cove’s first results, later pub-
lished as his Ph.D. dissertation, were damning:
woodrat population density was inversely propor-
tional to the number of feral cats on the landscape. If
cats were around, woodrats generally were not, and
any that were behaved differently than is typical.
On reviewing the results, Hershey bristled at the
implication that she was part of the problem. After
all, she had spent two decades working tirelessly to
reduce cat numbers while no one at Crocodile Lake
offered help. “I honestly didn’t know what more we
could do,” she says. Cove switched tactics. He want-
ed to show that the population decline that comes
with TNR is still too slow to save vulnerable species
such as the woodrat. As Marra explains, “If you put a
cat back in the environment, it’s going to keep kill-
ing.” When Cove analyzed cat fur found in the wild-© 2020 Scientific American