Jennifer
L. McDonald is an ecologist by profession and a cat person by
avocation. Some years ago, Tiggy, her ginger-and-white shorthair, would
bring home freshly killed mice and shrews for her consideration.
Dr. McDonald, now an associate research fellow at the Center for Ecology and Conservation
at the University of Exeter in England, was curious about the impact of
pet cats like Tiggy on wildlife. Fewer mice might be nice. But cats,
natural hunters, pounce on birds and rabbits, too.
“You
can’t pick and choose a cat’s prey,” Dr. McDonald said. If owners
realized how much prey their pets killed, she wondered, would they be
willing to contain their cats to protect wildlife?
She and her associates studied the question. The answer, published recently in the journal Ecology and Evolution was unequivocal and emphatic.
No.
In
recent years, debates about the predatory effect of cats on wildlife,
particularly endangered songbirds, have only intensified. But most
public opinion surveys have focused on the management of feral cats,
which make up the majority of domestic feline marauders, particularly in
the United States.
Dr.
McDonald surveyed owners in two British villages about cats they
allowed to roam outdoors. Owners were asked to predict the amount of
prey taken by their cats and document the actual killings. Owners in one
village were then asked whether they believed pet cats had an
ecological impact.
Researchers
also asked owners about their willingness to keep cats indoors during
prime hunting time, from dusk to dawn. The idea was flatly rejected,
with some owners providing unsolicited commentary: “My cat chooses for
herself whether to stay in or go out,” one wrote.
Pointing
to “a dissociation between actual and perceived predatory behavior,”
the researchers concluded that “the cat owners in this study reject the
proposition that cats are a threat to wildlife.”
Sara J. Ash,
a professor of ecology and conservation biology at the University of
the Cumberlands in Williamsburg, Ky., said that the results highlighted
the deep divide between cat owners, who see their individual animals as
doing what comes naturally, and ecologists, who view cats as a
predatory, nonnative species.
“These
owners think, ‘My cat only kills two mice a day,’ ” Dr. Ash said. “But
they don’t think about the high density of well-fed cats throughout
their neighborhood.”
The
study’s cat owners were generally able to predict whether their pets
would bring home prey, but they fared poorly at estimating how much.
Among 43 cats tabulated in the Cornwall village of Mawnan Smith, the
average monthly catch ranged from none to 10. Over four months, the cats
delivered a total of 325 animals: Nearly 60 percent were rodents, and
27 percent were birds.
(According to researchers, 6.2 percent were
unidentifiable.)
Although
Mawnan Smith and another village in the study, Thornhill, in Scotland,
are in rural settings, these owners’ reactions corresponded with those
of urban cat owners in Britain. In a 2012 study, they said
overwhelmingly that they did not believe cats depleted certain bird populations.
John Bradshaw,
a professor of anthrozoology at the University of Bristol in England,
pointed out that the owners in this latest study counted only the prey
their cats had brought home, and did not know how many creatures the
cats might have left elsewhere — scenarios vividly illustrated in a 2013
University of Georgia study by researchers who attached “kitty cams” to 55 pet cats. Those cats left behind nearly half the prey they had killed.
But Dr. Bradshaw, the author of “Cat Sense,” questioned whether cats were really having an ecological impact.
“No
doubt pet cats kill lots of little animals, but are they doing
long-term harm in the United States and Britain?” said Dr. Bradshaw, who
feels that the evidence is “flimsy.”
Some
researchers argue that while cats do have an impact on endangered
species, notably on oceanic islands with few indigenous predators, the
danger they pose in Europe and North America is hardly as significant as
housing development, drought or pollution.
Noting
that the biodiversity threat was insufficient to persuade owners to
keep their cats indoors, Dr. McDonald and her colleagues suggested a
different tactic: emphasizing the deadly hazards to pets that wander at
will from, road traffic, for example, and larger predators.
Increasingly, in the United States, that has meant coyotes.
According to a new study in The Journal of Mammalogy, cats, and possibly some owners, are getting the memo.
American wildlife researchers investigated whether cats, which they
assumed hunted mainly in residential areas, were also foraging in parks,
where biodiversity is richer. Or were cats avoiding those areas because
of coyotes?
With
nearly 500 volunteers, researchers placed cameras in 32 parks and one
urban area in six states, recording cat and coyote traffic. They found
that many coyotes, but very few cats, stalked those protected public
lands.
That was even true of Rock Creek Park
in Washington, D.C., which is surrounded by residences and likely
thousands of pet cats. Yet in six months, researchers caught coyotes on
camera 125 times in the park, but photographed a cat only once.
Perhaps
wary owners were keeping their cats indoors. “And maybe cats smelled
coyote urine, and it struck primal fear into their little pet hearts, so
they’re staying away,” said Roland Kays, the lead author and a research associate professor of wildlife and forestry at North Carolina State University.
But
cats and coyotes did overlap in what researchers described as “small
urban forests” — smatterings of woodland along greenways in suburban and
exurban neighborhoods where coyotes are encroaching.
Studies have shown that such encounters may not end well. “Letting the cat out is not only a risk to the birds but to the cat,” Dr. Kays said.
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