Cats, tilting at windmills, & what goes around comes around

From ANIMAL PEOPLE, November/December 2013:

 

WASHINGTON D.C.––Did inflated claims about cat predation on
birds give the U.S. Fish & Wildlife Service political cover for granting
a 30-year exemption from prosecution to wind power developers whose
turbines kill eagles?
The exemption was announced on December 6, 2013, two weeks to
the day after Duke Energy Renewables agreed to pay $1 million in
settlement of charges resulting from the deaths of 14 golden eagles and
149 other protected birds at wind farms near Casper and Campbell Hill,
Wyoming between 2009 and earlier in 2013.
Wind turbines in the Altamont Pass east of the San Francisco Bay
area in California are believed to kill about 60 bald and golden eagles
per year. Other wind farms around the U.S. are known to have killed at
least 67 eagles since 2008.


At the same time as granting the exemption for killing eagles,
the Fish & Wildlife Service approved a plan by Beech Ridge Energy to
minimize and mitigate the effects of a southern West Virginia wind farm
on endangered bats and birds.
National Audubon Society president David Yarnold and American
Bird Conservancy president George Fenwick immediately denounced the
exemption for eagle deaths. The American Bird Conservancy also rushed
to amplify a projection by ornithologists Scott Loss, Tom Will, and
Peter Marra that wind turbines are already killing 140,000 to 328,000
birds per year, and may kill as many as 1.4 million birds per year by
2030. The Loss, Will, and Marra projection is seven to sixteen times
higher than most previous estimates of mortality among birds caused by
wind turbines, but much lower than estimates of 440,000 projected by
Albert Manville of the Fish & Wildlife Service in 2009 and 573,000
projected by California ecologist K. Shawn Smallwood earlier in 2013.
But Loss, Will, and Marra in January 2013 alleged that
domestic cats in the U.S. kill up to 3.7 billion birds per year. The
findings were trumpeted to mass media by the American Bird Conservancy
without a mention that Loss, Will, and Marra used projected cat
numbers that were more than four times the most plausible figures that
could be drawn from actual cat population surveys, and included a
projection of the U.S. feral cat population based on research published
more than 80 years earlier.
Their projected estimate of cat predation was therefore
magnitudes of order higher than the estimate of 100 to 125 million birds
killed by cats per year issued by Manville in 2002.
“For several years now, the National Audubon Society and
American Bird Conservancy have co-opted, twisted, and misrepresented
any scrap of published science they could find—however
indefensible—suggesting that cats might have an impact on bird
populations,” commented Vox Felina blogger Peter Wolf. “But what
if their campaign has been too effective—with the wrong audience?”
Acknowledged Wolf, “Unfortunately, there is no way to tell
if all of this campaigning against free-roaming cats and TNR had
anything to do with [the Fish & Wildlife Service eagle decision] which,
sadly, will likely mean the deaths of more eagles. But seen against
the alleged impacts of cats, wind turbines seem utterly benign.”

Cats & coyotes

The most recent major study of cat impact on wildlife,
meanwhile, concluded that “Estimates of the ecological impact of
cats, extrapolated over large geographic areas, are likely to
overestimate the impact of cats if the effects of interference
competition by coyotes are not considered.”
Entitled “Population Ecology of Free-Roaming Cats and
Interference Competition by Coyotes in Urban Parks,” the study by
wildlife ecologists Stanley D. Gehrt, Evan C. Wilson, Justin L. Brown,
and Chris Anchor appeared in the September 13, 2013 edition of the
online journal PlosOne.
Gehrt et al “focused our research on free-roaming cats
inhabiting patches of natural habitat within the northwestern suburbs of
the Chicago metropolitan area,” they wrote. They trapped and
radiotagged 39 cats in 2008-2009 at the Max McGraw Wildlife Foundation
preserve in Kane County; the Poplar Creek Forest Preserve, Beverly
Lake Forest Preserve, Ned Brown Forest Preserve, and the Spring Valley
Nature Preserve, all in Cook County; and at the Prairie View
Conservation Area and Pleasant Valley Conservation Area, in McHenry
County.
Gehrt et al caught 43 cats in all, among them 18 adult
females, 19 adult males, and five kittens, two male and three female.
Among the adult cats, four of the males and five of the males had been
sterilized, apparently all in connection with a neuter/return program
at the Spring Valley Nature Center.
Eight cats (20%) died during the study, nine “were removed
from the system by cat advocates opposed to our research,” Gehrt et
al wrote, (abduction), eleven cats were either adopted or otherwise
“legally removed,” the transmitters on five cats stopped
broadcasting, and the rest disappeared before the end of the study.
Gehrt has continuously monitored radio-collared coyotes at the
seven study sites since 2000. Thirty-three coyotes were known to be
using “all or portions” of the study sites while the cat research
was underway.
“Radio-collared cats were located via triangulation from
truck-mounted antenna arrays,” Gehrt et al recounted. The radio
transmitters “included a mortality switch and we attempted to collect
carcasses of cats as quickly as possible, usually within 24-48 hours,
following indications of mortality. We submitted cat carcasses to the
University of Illinois Zoological Pathology Program. Carcasses were
necropsied to determine the cause of death, and to identify any
contributing pathologies.”
Causes of cat death were divided among predation, roadkill,
disease, and unknown.

Cats prove healthy

“In general,” Gehrt et al said, “we found that
free-ranging cats were in better condition than we expected, with a
relatively high survival rate and low exposure to cat-related pathogens,
with the exception of toxoplasmosis gondi. There was little evidence
that transmissible diseases were important.” Blood testing “indicated
low exposure to FIV and FeLV.”
Gehrt et al noted “potential for cats to negatively impact
other species, including humans, through their transmission of
toxoplasmosis gondi.” But toxoplasmosis gondi is already widely
distributed among other mesocarnivore species in the Chicago
metropolitan area, Gehrt et al acknowledged, without visibly harmful
effect. About 60% of the striped skunks, 38% of the raccoons, and up
to 63% of the coyotes in the vicinity are seropositive for toxoplasmosis
gondi, according to other research by Gehrt.
“Although our trapping was conducted in natural habitat
fragments,” Gehrt et al wrote, “and therefore our sampling was
biased toward cats using fragments, our study animals appeared to live
primarily at the periphery,” of the habitat, “which was likely an
avoidance of coyotes, as coyotes selectively used natural habitats and
avoided developed areas. Our results support the notion that the
ecological impact of cats in natural habitat fragments is minimized due
to interference competition from coyotes. Consequently, the ecological
impact of cats in those areas, via predation of native species, also
was likely limited. However, we do not know the impact of cats within
the larger urban matrix, where coyote activity is relatively limited,”
Gehrt et al finished, wrapping up with the usual recommendation that
further research is needed.

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