A Plague of Frogs: The Horrifying
True Story by William Souder
Hyperion, $23.95, 299 pages.
The News & Observer
February 11, 2001
What is mangling the frogs?
By Phillip Manning
On a warm summer day in 1995, Cindy Reinitz took her middle-school
class on a field trip to a farm just outside Henderson, Minn.
The 600-acre mosaic of bucolic woodlands, prairie and farm fields
entranced teacher and students. As they strolled toward a pond,
hundreds of small frogs leaped from beneath their feet. The kids
began grabbing at them. Jeff Fish, a freckled-face 13-year-old,
caught the first one; it was missing a hind leg. On that day,
the students caught 22 frogs. Eleven of them were deformed.
Reinitz contacted the Minnesota Pollution Control Agency, which
dispatched a herpetologist to the site. Twenty percent of the
frogs he collected were missing legs or were cruelly deformed.
One frog he examined appeared to be missing an eye. But the herpetologist
eventually found it -- dangling from a fleshy stalk attached to
the roof of the frog's mouth. A few weeks later, frogs with five
or more legs were reported in another Minnesota lake. During the
next two summers, huge numbers of deformed frogs were found all
over Minnesota, in many other Northern states, and in Canada.
Soon, the local and national media were reporting stories that
focused on two questions: Were the malformed frogs a harbinger
of environmental disaster, and could the cause of their problems
endanger us? But as William Souder, who covered the story for
the Washington Post, recounts in "A Plague of Frogs,"
scientists could only begin to answer those larger questions by
addressing a smaller one: What was mangling the frogs?
His well-written and informative book tells the tale of the frogs
and the very different approaches researchers took to discover
what was crippling them. Nowadays, we expect science to be able
to answer every question, but Souder reminds us that even seemingly
small problems are difficult to solve. And environmental problems
are especially hard because -- unlike in a laboratory -- they
involve many variables that cannot be controlled.
Gradually, the scientists broke out into three camps. One group
believed that a parasite was causing the problem. Pieter Johnson,
a senior at Stanford University, surveyed 15,000 amphibians taken
from 35 ponds in California. At four of the ponds, 25 percent
to 45 percent of the frogs were malformed. The other ponds yielded
only normal frogs. Johnson found that the four affected ponds
were the only ones that harbored a parasite known to cause deformities
in frogs. When he examined the deformed frogs, he invariably found
parasites. He then confirmed his field work in the laboratory.
He added parasites to water containing normal tadpoles and was
able to produce the same deformities he observed in the field.
Parasites, he concluded, were the problem. Case closed? Not quite.
While Johnson was studying frogs in California, Joe Tietge, a
scientist at the Environmental Protection Agency, was conducting
a series of experiments using ultraviolet (UV) radiation. He showed
that tadpoles exposed to UV radiation developed into deformed
frogs. Of course, tadpoles have been exposed to UV rays from the
sun for millions of years. What was new? Was the thinning ozone
layer admitting more UV radiation? Some investigators thought
so, but there was no proof that this was what was occurring in
the wild. Still, Tietge's research established that UV rays could
create the kinds of deformities observed in the field.
The third theory came from Quebec. Three years before deformed
frogs were discovered in Minnesota, Martin Ouellet, then a 23-year-old
graduate student at McGill University in Montreal, found a frog
with a withered hind leg in a farm pond near Montreal. Frogs became
his passion. By 1997, Martin Ouellet had examined more deformed
frogs than anybody else in the world, all of them caught in the
heavily agricultural area along the St. Lawrence River. One day,
in a single wetland surrounded by farm fields, he caught more
than 100 frogs, and about 60 percent of them had missing, mangled
or extra legs.
He searched out pristine locations, far from any farms, to use
as control sites. He found no deformities in the frogs at these
sites. Martin Ouellet suspected -- no, was certain -- that the
problem was pesticides. When confronted with the parasite data,
he shrugged it off. Parasites are everywhere, he said. "But
deformed frogs are not everywhere. Why do I not see these missing
legs in my control sites?" It was a question no one could
answer.
Perhaps, Souder suggests, the case of the deformed frogs is just
one piece of a bigger puzzle. Amphibians around the globe are
in decline. Frogs are disappearing from pristine areas, from agricultural
areas, from everywhere. From Canada to Costa Rica, from Japan
to Germany, frogs are vanishing from the earth. One Minnesota
lake had hundreds, perhaps thousands, of mink frogs when the first
abnormalities showed up in 1995. A year later, there were fewer
mink frogs, and half of them were deformed. Three years after
that a professional herpetologist could find only 16 mink frogs
at the site, all grotesquely deformed.
What is happening to the frogs? Everything. Global warming caused
the extinction of the most famous (and most beautiful) frog in
the world -- the golden frog of Costa Rica. There is little doubt
that parasites and pesticides are playing a role, as is increased
UV radiation. One scientist said he thought the ultimate cause
of the frogs' decline was due to "a convergence of environmental
misfortune." And he was almost certainly right.
Souder nicely pulls together all the suspects in the frogs' decline,
which is what makes this book valuable. "The frog,"
he writes, "has sensed a change, a displacement in the order
of life as we know it. We may be responsible, in part, for causing
this change. And we may be the next to feel it. The frog is telling
us something. Will we listen?"
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