Hundreds of Deformed Frogs Pose Environmental Warning
By William Souder
Special to The Washington Post
Monday, September 30, 1996 ; Page A01
On Aug. 8, 1995, teacher Cindy Reinitz took a group of her middle-school students on a
field trip to a farm in the town of Henderson in south-central Minnesota. As they walked
along, the kids started chasing frogs. Jeff Fish, a red-haired, freckle-faced 13-year-old,
caught the first one that didn't look right.
"When I picked him up I saw that he was missing his right hind leg," said
Jeff. "My first instinct was that a predator had bitten it off. But I looked him over
for sores or scars and I didn't see any so I showed him to the teacher."
As Reinitz examined the amphibian, a girl brought over another frog, this one with a
withered hind leg. Then another. All told that morning, the class caught 22 frogs, 11 of
which had deformed hind legs. "I think the kids got kind of scared," said
Reinitz. "They immediately started asking me what the cancer rate was in the
Shaken, Reinitz alerted a local wildlife biologist and the frogs eventually were
reported to the Minnesota Pollution Control Agency in St. Paul. It would be the first of
many such reports the agency would receive in the coming months.
Deformed frogs have now been found at more than 100 sites in 54 of Minnesota's 87
counties, and researchers here believe they're everywhere in the state. Deformed frogs
have also turned up across Wisconsin and in the St. Lawrence River Valley in Quebec.
Last week, as Minnesota's frogs began heading for their wintering locations on the
bottoms of deep lakes and rivers, where they rest atop one another in large piles,the
Environmental Protection Agency convened a conference of scientists in Duluth. Val
Beasley, a professor of veterinary medicine at the University of Illinois, told the group
of more than 60 researchers what they all already seemed to be thinking.
"Are we concerned about the animals as a monitor of conditions that would cause us
concern for humans?" Beasley asked. "Or are we worried about the animals in and
of themselves? I think the answer is that we're worried about both."
Joe Tietge, the EPA research biologist who organized the conference, said he was unsure
how to label the problem just yet. "It's certainly safe to say it's an environmental
problem," he said. "It's just not normal to see deformed animals."
Nor is it pleasant. Scientists at last week's conference were appalled at the graphic
evidence presented to them -- most notably by photographs of hideously deformed frogs
shown by David Hoppe, a herpetologist from the University of Minnesota's Morris campus.
Hoppe is a member of a research team from the university and the pollution agency that
received an emergency grant of $123,000 from the Minnesota legislature to study the frog
problem this past summer.
The team, which could scarcely keep up with the reports pouring in from all over the
state, found frogs with missing legs, extra legs, misshapen legs, paralyzed legs that
stuck out from the body at odd places, legs that were webbed together with extra skin,
legs that were fused to the body, legs that split into two half-way down. They also found
frogs with missing eyes. One memorable specimen was a one-eyed frog that turned out to
have the second eye growing inside its throat.
Hoppe's most important find was at a site in Crow Wing County, in the heart of
Minnesota's most popular lake vacation district. In a small, seemingly pristine lake,
Hoppe found abnormalities in five species of frogs and one toad. Significantly, the mink
frog, the species with the highest incidence of deformity at around 50 percent of the
total, is the species that spends the most time in the water. American toads and wood
frogs, which were the least aquatic species, had rates of deformity under 5 percent.
"Mink frogs are rarely more than a jump away from the water," said Hoppe,
"and as tadpoles they don't metamorphose until their second year. What I found at
this site was a really gross-looking batch of mink frogs."
Hoppe brought one back to his laboratory in Morris -- a mink frog his students
nicknamed "Scrunch" because its hind legs were nothing but a tangle of flesh
festooned with clusters of feet and toes. Despite perfect conditions and careful hand
feeding, the frog died within two weeks.
The same will happen to virtually all of Minnesota's deformed frogs, which turn up in
smaller and smaller numbers as the season progresses. Frogs with compromised limbs cannot
feed themselves or escape from predators. Hoppe said it's rare to find an adult frog with
a substantial limb abnormality.
In the meantime, Hoppe concedes that nobody knows what to tell people in Minnesota who
want to know what all this might mean to them.
"The landowner up in Crow Wing County asked me if he should stop his kids from
swimming in the lake," said Hoppe. "And I had to say that I just didn't know.
But I told him that I wouldn't let my kids near it."
`An Animal Love Canal'
"At first I thought this was no big deal," said Robert McKinnell, a
geneticist and cancer expert at the University of Minnesota who's been doing research on
frogs since 1958. "In my experience, you occasionally find abnormal frogs wherever
you find frogs."
But then McKinnell visited the Henderson site with his longtime colleague David Hoppe.
Together, over the years, they've collected nearly 20,000 frogs in the wild. This time
they found deformed frogs "everywhere." When a second site was reported 100
miles to the north, they went to that one too, with similar results. One survey of the
pond counted abnormalities in 91 of 94 frogs.
At both sites, the frogs were found on farms in and around ponds that had recently been
excavated -- which led McKinnell to wonder about contaminants in the bottom sediments that
could have been stirred up. He began having uncomfortable recollections of work he'd done
back in the early 1980s, when he was one of the researchers who confirmed chromosomal
abnormalities in people living near Love Canal. Chemical contamination drove more than 800
families from that Niagara Falls, N.Y. neighborhood in the 1980s.
"Once I got a look at these first two sites," he said, "I thought we
just might be dealing with an animal Love Canal."
Tissues from Minnesota's deformed frogs have been undergoing chromosomal analysis at
Augustana College in South Dakota. So far, the results are negative -- suggesting that the
deformities are not genetic mutations but rather developmental abnormalities that begin in
the egg or tadpole stage prior to metamorphosis.
But McKinnell remains worried. Frogs, he said, serve as a "sentinel species"
because many of their metabolic functions -- notably in the liver, where a variety of
agents are processed out of the body -- are similar to the same processes in humans.
"Now the whole state appears to be affected," he said. "We should be
The possibilities raised at last week's conference appear almost limitless. Early
evidence points to something in the water where the frogs breed and develop, and in which
they spend every stage of life. Their skin is highly permeable: What gets in the water can
get into the frogs. Two theories, which may ultimately become one, are receiving the most
One is that the frogs have become infested with naturally occurring parasites. Stan
Sessions, a biologist from Hartwick College in New York, has demonstrated an apparent
cause-and-effect relationship between a common parasite called a trematode and the
development of extra limbs in frogs that were found in ponds in Northern California a few
years ago. In Sessions's explanation, cysts form around the parasite after it enters a
tadpole. The cysts in turn disrupt the development of emerging limbs, causing two to
sprout where one should.
But most of the conferees were skeptical that parasites alone could explain the wide
diversity of malformations in Minnesota's frogs -- and so, in the end, was Sessions
himself. "I came here convinced that parasites were the cause of deformed
frogs," Sessions said. "But what I've heard here is causing me to think that
environmental degradation is somehow contributing."
The researchers believe that the most probable cause of that degradation is some kind
of chemical pollutant. One study from Canada has established a relationship between frog
deformities and the local use of farm pesticides.
Also on the table as possible causes are viral or bacterial disease, the presence of
various heavy metals known to cause birth defects, acidification of the water, and even
increasing ultraviolet radiation as the Earth's ozone layer is depleted.
Judy Helgen, a research scientist and water quality expert with the Minnesota pollution
agency who's led the investigation to date, said she believes the focus will eventually
come down to chemicals of some kind.
But she has no answers yet. "One couple asked me if they should close on a house
after they saw deformed frogs near it. Another time, a pregnant woman who had seen some
abnormal frogs called wondering if she was safe. The answer is that I don't really
In the interim, Joe Tietge says the EPA will almost certainly get involved in the
research -- which he said is likely to take several years.
"Part of it is that you can only study the frogs for a limited amount of time each
summer," said Tietge. "But what will really take time in establishing a cause is
the complexity of the problem. You need trend data -- and that takes a while.
"Plus, if it turns out to be a chemical problem, then we'll have to do a risk
evaluation for humans. After all, frogs are vertebrates and so are we."
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