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THE MINNESOTA RIVER TRACES A DEEP V ACROSS SOUTHERN Minnesota. From its headwaters at Big Stone Lake on the South Dakota border, the river runs southeasterly beneath enormous skies, crossing an open landscape of empty, windswept horizons. In places here you can see the curvature of the earth. Flowing through scrubby remnants of the great prairie and down into fertile corn and soybean country, the river follows the ancient streambed of one of the mightiest watercourses that ever existed—the river Warren, which 12,000 years ago drained glacial lake Agassiz. One hundred and fifty miles downstream the Minnesota angles sharply to the northeast and heads for the Twin Cities, where it joins the Mississippi. A muddy slurry of silt, farm runoffs, arsenic, lead, selenium, cadmium, and PCBs, the Minnesota is one of the most polluted rivers in the country.
But along the second half of its length the Minnesota travels through a valley that is on either side broad and verdant and flanked by lovely wooded bluffs. In the summertime the valley is arrestingly lush. A section above the town of Le Sueur is still claimed by the Pillsbury company as the "Valley of the Jolly Green Giant." It was near here, on August 8, 1995, that a group of eight middle school students on a field trip made a shocking discovery.
The day was humid and overcast. It looked like rain. Most Minnesota schoolchildren were still enjoying the last weeks of what had been an unusually hot summer vacation. But at the progressive New Country School in Le Sueur, where classesare in session year-round, a forty-year-old teacher named Cindy Reinitz loaded her nature studies group into a van at 8:30 in the morning. Reinitz and the kids, who were from grades six, seven, and eight, headed north on Highway 93 as a warm drizzle began to fall.
They were going to a farm owned by Donald Ney. Six hundred acres of rich Minnesota loam situated atop the bluff on the east side of the river, the farm overlooks the little town of Henderson far below on the opposite bank. Carved from the woods in the 1850s, the Ney farm is one of the oldest in the area. Don Ney, who was born in Chicago, came here in 1952 to live with his bachelor uncle and two spinster aunts—an arrangement he maintained had put him "under their thumb" for most of the rest of his life. A short, round man in his mid-sixties, Ney was shy but possessed of a ruddy, reticent charm. Never married, his only real passion in life was the land that had finally passed into his hands. More or less. Just before the last aunt died in 1991, she donated 350 acres of the property to Le Sueur County for use as an environmental learning center. Ney figured the gift was probably part of some complicated larger plan to prevent him from gaining total control over the original farmstead. Even so, the result pleased Ney enormously. He was delighted that people, especially children, routinely visited his farm to hike the fields and scramble along its wooded ravines.
Reinitz knew the Ney farm well. She and her family owned forty acres just a half mile to the east, separated from the Ney place by a winding stretch of woodlands and by seven acres of replanted prairie tallgrass that Reinitz frequently wandered over. A tall, attractive woman with long red hair and a purposeful stride, Reinitz planned this morning to take her students on a walk into the woods rising above a creekbed between her property and Ney's. Some of the trees in the area are vestiges of the Big Woods, the towering hardwood forest that formerly covered much of south-central Minnesota. During the half-hour drive from the school, Reinitz watched the leaden skies roiling overhead and wondered to herself what they would do if the rain kept up. The students were a little wild already, arguing over which radio station to listen to and indicating little interest in the passing scenery they were about to explore. It was only Reinitz's second day with this class, and she sensed the kids were testing her.
To her relief, the rain had stopped by the time Reinitz arrived in Henderson around nine o'clock. She drove east over the low concrete bridge that crosses the river. The road curved sharply to the left and the van climbed a steep hill, then turned onto a long gravel driveway that ran along an expanse of undulating fields carpeted knee-high with soybeans. Reinitz drove in about a quarter of a mile and stopped at a field road. She got the kids out and they began to walk. Reinitz surveyed the countryside forlornly, thinking to herself that this trip, which had so often thrilled the third-graders she sometimes taught, might be a complete bore to these older children.
The field road, scarcely more than two well-worn tire tracks, was flat for a short distance. Then it fell steadily as the land gradually sloped away. Up ahead the road bent left, straightened again, and passed beside a massive, solitary ash. Just beyond the tree, in a large, bean-shaped depression, was a wetland. Don Ney could remember when they used to plant that section. But it was always wet and soft and a treacherous place for a tractor. In 1992, as part of the plan to create a nature center, Ney excavated the bottom of this low area, digging out nearly ten acres to create a pond. It is L-shaped, with two arms of roughly equal size and two small, round islands scraped up well out from shore. The pond collects rainwater that washes down the hillsides all around, and several underground drain-tile lines feed in subsoil moisture as well. The banks are a tangle of grasses and cattails and thistle that grows waist-high by late summer.
Reinitz and her class had gone only a few yards from the van when they began to notice small frogs, seemingly hundreds of them, leaping out from under their feet and into the wet, taller grass alongside the field road. The frogs were both green and brown, with darker spots, and looked to be only about an inch long through the body. But their jumps were prodigious, never coming just one leap at a time, but invariably in a blurry sequence of low-trajectory hops as the little frogs surged out of sight. As first one student and then another stuck a hand down to try to catch one, the frogs easily escaped. The kids scampered after them, and Reinitz felt her plan for the day slipping away. It was clear the students would rather do anything than go on the hike she had in mind.
As the class inched forward waves of small frogs continued to part before them as the animals darted right and left, often hard to see except as a sudden, vanishing movement in the grass that lined the edges of the field road. They were northern leopard frogs. Scientific name: Rana pipiens. It's a common frog in this part of the country, an important part of the often unseen ecology of a landscape dominated in the hot months by an orderly geometry of crops. Frogs are just one other living part of the yearly cycle in which the land is transformed after a long winter of dormancy. These frogs were juveniles, born that same spring and now newly metamorphosed and dispersing from the pond, spreading out overland in search of insects to eat. They were where they were supposed to be, doing what they were supposed to be doing, repeating an annual pattern that began hundreds of millions of years before the first humans tottered across the face of the earth. Jeff Fish, an enthusiastic, freckle-faced thirteen-year-old who had been literally diving onto the ground after the frogs, caught the first one that didn't look right.
The frog was missing a hind leg. Fish turned the frog over in his hand, thinking at first that the leg must have been bitten off by a predator of some kind. But there was no obvious sign of such trauma—just a continuation of smooth, normal-looking skin over the place where the leg should have been. The boy took the frog over to Reinitz.
Reinitz looked at the frog and at Jeff Fish with dismay. The animal felt cool and a little sticky in her hand as it struggled and kicked its one good back leg trying to escape. She was certain the energetic teenager must have somehow injured the frog in capturing it. But as she knelt and began to examine it more closely a girl in the class brought over another frog—this one with a hind leg that was strangely withered and stiff. Then another student came up with yet another frog with a missing hind leg. Perplexed, Reinitz stood on the hillside, sullen clouds riding low above her, and looked toward the pond. She recalled a visit she'd made to the farm on an excruciatingly hot day back in June, when there had been a great commotion in the pond. She remembered thinking at the time that there must have been large numbers of tadpoles thrashing the water. Now, looking at frogs up on the field that had missing legs or legs that could bend only a little or not at all, Reinitz was amazed that they could get around as well as they seemed to.
"Let's move down closer to the pond," Reinitz told her students.
Sure enough, although there were frogs all over the place there seemed to be more abnormal ones down by the edge of the pond, unable or unwilling to venture away from the water. The kids soon discovered that even frogs with significant leg abnormalities could be difficult to grab. They were quick, and easily navigated the prickly underbrush and the higher reeds at the border of the pond. But after about two and a half hours of chaotic lunging the students had managed to catch twenty-two frogs with their bare hands. Eleven of them had missing or abnormal hind legs.
By the time they had to leave, the students were scared. They talked nervously about the deformities and what they should do. As they walked back to the van, one of the kids asked Reinitz about the cancer rate in the area. Thinking of her own home just through the woods a short distance away, Reinitz wondered about that, too. Mentally she went around the township, thinking of everyone she knew in the vicinity of the Ney farm, and found that she could think of several people with the disease.
Reinitz had another worry. As she talked it over with the students, everyone agreed that they had to report what they'd found right away. But Reinitz didn't think anyone would believe their story unless they kept at least some of the frogs as proof. One of the students hit on the idea of photographing them with the school's new digital camera and posting the pictures on the Internet to see if anyone knew what might have caused the deformities. Reinitz rummaged through the van and found an empty five-quart bucket for Blue Bunny vanilla ice cream. The kids put three of the frogs—two abnormal ones and one that appeared to be all right—in the container and took them back to school. Still shaken, Reinitz began making calls the next day, trying to determine where a person reports having found deformed frogs. Eventually she got ahold of the Minnesota Pollution Control Agency in St. Paul.
* * *
I live about seventy-five miles from Don Ney's farm, in country just outside of the Twin Cities that doesn't look much different from the country around Henderson. Our land is bordered on one side by a farm. Each year a crop of corn or soybeans or sometimes pumpkins rises just feet from where our backyard stops. On the other side of the property is a large pond. It's home to ducks and waterbirds and muskrats, plus an assortment of frogs and toads. In recent years it has seemed that the frogs—especially the handsome, strong-limbed Rana pipiens I always used to see along the banks—have dwindled. Anyway, I rarely see them anymore.
Like many in Minnesota, my family has an abiding relationship with the outdoors. Despite the ugly outward sprawl of the cities—as lamentable here as anywhere—Minnesota is still mostly open space. The state was widely logged off or converted to farmland a century ago, but plenty of it remains wild today. Our children could name a dozen birds before they could read. They're not surprised to see a turtle excavating a hole in the yard to lay its eggs, or to find a garter snake basking by the swing set. They know the true darkness of the night sky, the frozen fire of moonlight, and what it's like to stand in a forest so quiet you can hear your own pulse. They know when the owls nest and how to look for the white head and tail on a bald eagle as it wheels overhead beneath the sun. We eat the raspberries that grow wild at the edge of the woods and fill our freezer with the fish we catch in the summer and the game we shoot in the fall. We're at ease with nature, and take some comfort in the belief we should be.
This sense of environmental well-being is reasonable. The evidence all around us is that the same force that has done so much to compromise the natural environment—human progress—is also what will save it in the end. A culture that can travel into space and chat on the Internet ought to be able to resolve low-tech issues like pollution or the occasional outbreak of birth defects in a wildlife population. We know what's in a rock from the moon; surely we can know what's in the pond by the side of the road and whether it poses a threat to anything or anyone. For a few decades now, at least, we've begun to police ourselves, restoring the air and water and the earth itself to an approximation of the way it would be in the absence of us.
Or so it would seem.
In fact, the environment is bigger, more complex, more difficult to manage than we might imagine, and the array of government agencies and regulations directed toward that end are far from a perfect answer. In many ways, we do know less about nature and biology than people generally believe. We're also much more tentative about what to do when a new sort of problem turns up.
Cindy Reinitz's call to the Minnesota Pollution Control Agency set in motion a chain of events that would eventually involve scientists and regulators from all over the country. But there was no special reason why this massive investigation started out the way it did.
The MPCA at that time had no particular interest in amphibians; no one on its staff worked with frogs. But someone there had handled a similar call two years before. Reinitz was told to speak with Dr. Judy Helgen, a research biologist in the agency's water-quality division. A provisional employee of the MPCA whose work was funded by outside sources, Helgen's area of expertise was invertebrate biology. Bugs, snails, that sort of thing. At the time she was engaged in a long-term project in which she was trying to develop a wetland index based on various invertebrate species that can serve as "bioindicators" of environmental conditions.
In the fall of 1993, Helgen had looked into a report of deformed frogs near Granite Falls, another town on the Minnesota River, to the west and considerably upstream from Henderson. A resident there claimed to have seen a number of young leopard frogs during the summer that suffered from various limb abnormalities—both extra and missing legs—plus a few that were missing eyes. The MPCA and the Minnesota Department of Natural Resources went out to investigate and managed to catch a handful of abnormal animals. It was sufficient in the researchers' minds to confirm the citizen's report, but nothing more came of it. Analysis of soil and tissue samples turned up mildly elevated levels of arsenic, but that surprised no one familiar with the Minnesota River watershed. Besides, the levels were thought to be below the threshold that would impact the animals. The following spring the frogs in that area appeared normal.
Reinitz was told that Helgen would be interested in what her class had found on the Ney farm. But Helgen was away from the office that week, working in the field with the U.S. Environmental Protection Agency. Reinitz left her a message in voice mail. On August 14, the day she returned to the office, Helgen phoned Reinitz. Each woman would later recall the conversation a little differently.
Helgen says she was immediately alarmed because of the similarity between what Reinitz described and what had been reported at Granite Falls. But if she was worried, she didn't let on. Reinitz thought Helgen sounded more skeptical than alarmed. She says Helgen was polite but didn't seem too impressed because of the relatively small number of frogs the students had caught. Still, Helgen said she would send someone out to have a look, and she did.
The next day, August 15, Helgen asked one of the MPCA's summer interns, Joel Chirhart, to drive down to the Ney farm and see if he could find some frogs. Chirhart, a twenty-three-year-old student worker originally from St. Cloud, had only recently moved back to Minnesota from Texas, where he'd been studying biology. Chirhart couldn't think of any reason why Helgen would send him out to examine frogs, other than the fact that he happened to be available and she was busy.
Chirhart left the MPCA's headquarters in St. Paul around three that afternoon, driving one of the agency's blue Plymouth Voyagers with the words State of Minnesota on the side. The weather had turned hot again, and during the ninety minutes or so it took him to make his way south out of the cities and down to Henderson, Chirhart became convinced he was wasting his time. He wondered what was going on. None of it even made sense. Just a bunch of kids who claimed they'd caught some frogs that weren't normal. Looking out over the wilting countryside, Chirhart doubted he'd be able to find any frogs at all on such an oppressive, sticky afternoon.
At the farm, Chirhart went down the long driveway and then turned onto the field road. The blue van rocked slowly down toward the pond under the blistering sun, soybeans fluttering wanly in its wake. Cindy Reinitz was waiting just beyond the big ash tree. Chirhart parked the van, got out, and introduced himself. He and Reinitz started looking for frogs—which turned out to be everywhere in spite of the heat. They caught frogs along the edge of the field road, in the higher grasses, and near the banks of the pond. They caught so many so easily—more than a hundred—that Chirhart didn't even bother to count them. He could scarcely believe what he was seeing. After about two hours, Chirhart walked back to the van and got on a cell phone to Judy Helgen.
"I think you're going to want to get down here right away," he told her.
|PART ONE: The Hell|
|2: From Here to There||11|
|3: Creepy Crawly||21|
|4: Surprised but not Crazy||47|
|6: When the Fish Began to Walk||70|
|7: Rumors, Theories, Rules of Engagement||80|
|8: Choosing Sides||107|
|9: The Biggest Experiment Ever||126|
|PART TWO: Famous Last Days of the Golden Toad|
|11. Bad Weather||186|
|12: "We've Found Something in the Water"||207|
|13: Bad Boy||239|
|14: The Green Mountain||262|
Dennis Bock was born in Brainerd in 1951 and grew up there just blocks from the Potlatch Corporation, a paper company where he now works in the coating department. When he was eighteen, Bock's parents moved out to the country east of town, near Nokay Lake and the place where Dennis's grandfather had built a homestead early in the century. About the time they moved, Dennis met Rhonda Wiltz, a quiet, pretty brunette who was in the ninth grade. They didn't date until some years later, but Dennis recalls that he "kept track of her" all along.
In the fall of 1977 Dennis and Rhonda became engaged and started looking for some land near his parents' place. There didn't seem to be much around that they could afford. Out of the blue Dennis's grandmother offered to sell them a small section of her property. The deed claimed about thirty-five acres, but one stretch of the boundary ran through a lake bordering the east side of the property, and back in the 1930s a dairy farm next door had encroached from the north. The actual remaining area of dry land worked out to something like twenty-six acres. Dennis had always secretly hoped they'd end up there some day. He and Rhonda were thrilled.
The Bocks began clearing the property for a house that fall and started building the next summer after their wedding. They moved in finally in 1979 at Thanksgiving and have lived there ever since. Rhonda, who used to work as a nurse, has tended the home and their growing family--Eric, Jennifer, Troy, and Brandon--plus Buster, a plump, good-natured golden retreiver, and a cat with no name that skulks about and jumps into cars whenever anyone drives up and opens a door. Dennis works rotating shifts at Potlatch. He's a wiry, intense man, with a gentle manner and a lively, agile mind. He's also fastidious, and every inch of the property and the house is always in perfect order.
For years, the Bocks lived the kind of dreamy, unruffled middle-class lives that most of us imagine as rare yet somehow archetypally American. A big part of this picture was the timeless symmetry of the rural setting. The Bocks' house--a sunny yellow five-bedroom split-level--faces south at the end of a long, flat, gravel drive. It's surrounded on three sides by a large yard with neatly tended flower gardens front and back, and an ample vegetable garden near the woods.
About sixteen acres of the property are leased to the dairy farmer next door, who plants clover or alfalfa and sometimes corn on either side of the driveway and out to the west edge of the property. In the summer of 1997 the Bocks made about $30,000 worth of improvements, including a blacktopping of the parking area near the house and the addition of a large sheet-metal pole barn where Dennis keeps his boat and the four beloved snowmobiles the Bock family tools around on in winter.
The east side of the property is wooded, a mix of oaks, maples, and pines mainly. A swath of lawn runs from the house down a steep hill to the bowl of the lake. The lake isn't named. But it's pretty good-sized, roughly thirty acres in area, and almost perfectly round. There are no other homes on the lake, no other manmade structures of any kind visible from the water. The woods ring the shoreline seamlessly, except for a spot about a hundred yards north of the Bocks' where the cows come down to the water. There's an electric fence extending out into the water to keep the herd where it belongs. The bank there is open and softly trampled down.
The lake is spring-fed, the waters brownish but relatively clear over a muddy bottom that is easily roiled. Lily pads and reeds grow out from the shore and rock gently in the waves when the wind kicks up. Dennis and Rhonda say they've been all over it and have never found any spot in the lake to be deeper than about ten feet.
The Bocks have a twenty-foot dock and keep a two-person paddleboat beached alongside it. For most of the time they have lived here, the kids swam and played in the lake, and the whole family for many years enjoyed fishing for sunfish, which they love to eat. Usually the fishing was good, though sometimes the panfish were less plentiful after an especially harsh winter. Dennis and Rhonda have often seen eagles taking larger fish from the lake, too.
The Bocks put their first well near where the vegetable garden is. It was fifty-seven feet deep, drawing water from a subterranean layer of fine sand. The well caused the Bocks nothing but headaches. Like much of the well water in this part of Minnesota, theirs was loaded with iron--so much iron that a heavy, rusty sludge filled the pipes in the house and the tap water ran red. In 1988 they sank a second well, right alongside the first, that went down ninety feet and terminated in a layer of coarse gravel. This was an improvement. Although there was still high iron content in the Bocks' water, their water softener made it clear and, so far as they knew, safe.
One day in July of 1995--about a month before Cindy Reinitz and her nature studies class visited the Ney farm--Dennis and Rhonda were sitting at the dining room table talking with friends and keeping a casual eye on the kids, who were outside. The Bocks' dining room overlooks the lake. It was late afternoon. As the adults chatted, Brandon, who was ten at the time, came up to the window holding something.
"Look at this weird frog!" he said.
The Bocks can't remember whether the frog had five legs, or maybe it was six, but Dennis is pretty certain it was a leopard frog.
"We didn't even really check it out," Rhonda told me when I talked with them two years later. "I guess we just assumed it was some minor freak of nature."
Dennis and Rhonda promptly forgot all about the frog. Even when they heard the news about the outbreak at Henderson a few weeks later, Brandon's discovery seemed little more than an ironic coincidence. But then in late August the kids found more deformed frogs--about a dozen or so. All of them were leopard frogs. All were juveniles. And all had extra hind legs. Dennis decided to take them to the local office of the Department of Natural Resources. He asked the kids to find something to put the frogs in, and they did--an empty ice-cream bucket.
The next day, Dennis took the frogs with him to work and showed them to his buddies at Potlatch. They were not impressed. They told Dennis they saw frogs like that "all the time." Figuring he'd make a fool of himself if he went over to the DNR, Dennis took the bucket out behind the plant, turned the frogs loose, and went back to work.
But then came more reports of more deformed frogs from other places around Minnesota. Rhonda felt they should contact someone, and finally she did call the local DNR office. The woman at the DNR said there was nothing their department could do about the frogs, but that she would pass on the information to someone who could. It was late August.
A couple of days later the Bocks got a call back. Dennis answered. The man on the line introduced himself as David Hoppe, a herpetologist at the University of Minnesota campus at Morris, about two and a half hours away from Brainerd. He explained that he was consulting with the MPCA on the investigation into the deformities and that the agency had asked him to follow up on what they had found.
Hoppe was very polite, but he seemed skeptical and asked Dennis a lot of questions--about the lake, about what the deformities looked like, about what kind of frogs they had been catching. This had become the pattern by now. Like McKinnell and Helgen before him, Hoppe found the descriptions of deformed frogs so improbable, so unlike anything he'd ever run across in years of fieldwork, that he couldn't quite get himself to believe what he was hearing. Even as the reports of deformities began to pile up, the researchers struggled with doubts that this could really be happening. Each new outbreak was greeted the same way: It can't be.
Dennis Bock got the impression that Hoppe thought his story was strange. He thought Hoppe sounded ambivalent about coming up to see the lake for himself. But they talked some more, and after awhile Hoppe said that it did in fact sound as if they were seeing some of the same things that were being reported elsewhere that summer. But he wasn't just going to drop everything and rush up to Brainerd. Hoppe said he was busy with the start of the school year. He would try to come up in early October.
Hoppe was dubious when he got off the phone with Dennis Bock that first fall of 1995. Bock sounded like a reasonable, intelligent person who must have seen what he claimed to have seen. But it was still so incredible. Hoppe had been following the news from Henderson from a distance, much as he had listened to the report from Granite Falls in 1993. Back then Hoppe had been contacted by the MPCA to help conduct a field investigation. But he never saw anything more than a blurry picture of some dead frogs in a bucket, and when he personally surveyed the site the following year he saw only normal frogs. This was, in Hoppe's view, hardly surprising. In all his time field collecting, Hoppe had never seen anything other than an occasional minor deformity among the thousands and thousands of frogs he'd handled--certainly nothing that affected a large percentage of an entire population.
In fact, Hoppe and McKinnell had gone out of their way a fews years before to suggest that the appearance of abnormal animals in nature is generally too rare to worry about. It was in a brief aside in an article on color variations in leopard frogs they published in a conservation magazine, The Minnesota Volunteer. "We are not looking for two-headed, six-legged, or otherwise freakish offspring born in ponds contaminated by radioactive fallout or toxic waste," they wrote. The year was 1991.
Four years later, Hoppe found himself contemplating the unthinkable. Although he was determined to remain neutral on the question of causes, Hoppe privately suspected that Helgen and McKinnell had good cause to suspect chemical contamination. He knew that in the days before commercial garbage hauling and sanitary landfills came to rural Minnesota, people disposed of everything in whatever hole or ditch or crease in the woods was available and out of sight. He couldn't imagine a frog pond anywhere in the state that wasn't within a mile of some old dumping area. Contaminated groundwater and pond sediments were probably pretty common. Although this didn't quite rise to the level of a working hypothesis for Hoppe, the idea was there, in the back of his mind, all the time.
Hoppe finally broke away from his teaching schedule one day during the first week of October. The long drive over to Brainerd was discouraging. Summery weather had held through most of September, but it had lately turned cooler. Hoppe hoped the day would warm up enough that he might find frogs congregating near the water, getting ready to hibernate. But there was a rawness on the wind now that made him wonder if he hadn't waited too long to go. When he pulled up in front of the bright yellow house he knew he had. The trees were pitching in a stiff breeze that pulled leaves from their branches in long swirls of autumnal color. Overhead the sky was gray and cold. Hoppe shivered as he stepped out of his car.
In an instant he forgot all about finding frogs. Instead, he stared in disbelief at the Bocks' lake.
Hoppe had expected some approximation of the farm ponds that Helgen and McKinnell had described to him weeks earlier--classic leopard frog habitat. Instead he found himself looking out over a nearly pristine, natural lake, maybe half a mile across and obviously deep enough to harbor a variety of species through the winter.
There wasn't a frog to be seen anywhere that day. Hoppe spent a long time talking with the Bocks, whose story held together, growing more credible and more detailed as he listened. The Bocks liked Hoppe right away. His straightforward, unpresumptuous manner was disarming. Hoppe seemed like a regular guy, with his jeans and his quiet way and the neatly combed hair that he kept trying to push down in the breeze. They were surprised at how eager he now seemed to investigate their lake. He asked for their permission to make it a study site in the future. Dennis and Rhonda told me later that it was almost as if Hoppe knew instinctively how important their discovery had been.
"He seemed to think our lake was unique," said Dennis. "That it was dissimilar to the other places they were exploring."
"Isolated," said Rhonda.
"Dave seemed real excited about that," Dennis added.
The Bock children had caught the deformed frogs on the lawn, and certainly they were leopard frogs. Hoppe explained that their lake should have some other species in it--like mink frogs and green frogs--that rarely venture out of the water. As disappointed as he was at not finding frogs that day, Hoppe told the kids to be on the lookout. If the weather warmed suddenly the animals might yet reemerge and he wanted them to call him immediately if that happened. Hoppe told the Bocks that whether the frogs showed themselves again that fall or not he'd be back in the spring for sure.
Dennis and Rhonda wondered how worried they should be. Although she'd been the one who insisted on reporting the deformities, Rhonda still thought they were most likely just a fluke--one of nature's occasional mistakes. Dennis wasn't so sure. He couldn't stop thinking about the old township dump.
There were at least two possible sources of ground contamination in the area. One was a small area near the south end of the lake where a former neighbor had disposed of trash, including batteries and other automobile parts, over a period of years. Dennis thought that didn't seem like too big a deal. The township dump was more of a concern.
In the early 1970s, Crow Wing County had built a central sanitary landfill, at the same time closing a number of smaller dumps throughout the area. One of them was quite near the Bocks' place--less than a quarter of a mile away. Dennis knew the site had merely been bulldozed over, that there had been no effort to clean it up or to remove anything toxic. Could something have leached out into the groundwater over the past quarter century that had now entered the lake? Dennis Bock spent the winter brooding about it.
Hoppe, meanwhile, went back to Morris and reported what he'd seen to McKinnell and Helgen, who were stunned. McKinnell told me later the outbreak suddenly looked even more frightening when they learned that it was not limited to small agricutlural wetlands and manmade ponds. The researchers knew that if the Bocks' report were true it was evidence of deformed frogs in the kind of natural lakes that number in the thousands across the Minnesota countryside and are heavily used for recreation. This changed everything. "We were right back at the beginning," McKinnell said. Which was to say, more in the dark than ever.
Just as with Granite Falls two years back, the MPCA had conducted a few simple tests on sediment and tissue samples from the Ney farm and some of the other Henderson sites. The results had been inconclusive. They asked around to determine which were the major farm chemicals in use in the area. Reinitz and her students took periodic pH and temperature readings at the pond, too. None of this advanced the investigation, and by late fall--especially after the Bocks' situation had come to light--Helgen realized that if her agency and any of the other researchers were going to continue to work on the deformities problem next year they were going to need financing for a much more rigorous field program.
As it happened, the Minnesota state legislature was willing to oblige. The powerful State House Committee on the Environment and Natural Resources was then chaired by the late Willard Munger, a nearly eighty-year-old representative from Duluth, who as a kid earned money catching and selling frogs for bait. Munger knew what was happening at Henderson and was determined to do something about it. In October and again in February, Munger conducted hearings on the frog problem, and among those who testified were Helgen, McKinnell, and Reinitz and several of her students. At one of the meetings, Munger thundered that frogs were an important indicator of environmental health and that the problems turning up at Henderson and elsewhere needed to be taken seriously by everyone. "Whatever is happening to these frogs should be a warning to us that we have to do a better job of protecting our environment so there will be something left for us in the future when we all get down the line a little," Munger said.
In early 1996, with Munger's help, the Minnesota legislature approved $151,000 to study frogs. Hamline University in St. Paul received $28,000 of that amount to initiate an education program for elementary and secondary school students. The rest went to the MPCA. Helgen planned to continue the preliminary assaying of water, sediment, and tissue samples. She also contracted with McKinnell for dissection and analysis of frogs that they planned to collect in 1996 with Hoppe, who was to conduct population studies at several sites in an effort to determine just how significant the problem actually was in the field.
In retrospect, this didn't seem like much money or, frankly, much of an investigation. But as McKinnell explained to me later, the researchers were hesitant to launch a more ambitious--and expensive--effort given the uncertainties and their own lingering doubts about what they were seeing.
As the state huddled through the deep freeze of winter, Helgen, McKinnell, and Hoppe made their plans for the coming field season. Given their experience at Granite Falls, they were understandably nervous. Something had happened. The question now was, would it happen again next summer? As spring shouldered its way in behind the last snows and the ice thinned on lakes and wetlands across the state, the scientists fretted.
"Just as soon as we got that funding from the legislature we started to worry," McKinnell remembered later. "What if when we went out the next summer all we could find were normal frogs?"
But this time the outbreak of deformed frogs did not go away quietly over the winter. As the summer of 1996 unfolded, reports of deformed frogs poured in from every corner of Minnesota. One by one, the counties on Bob McKinnell's map were colored in. Hoppe cautioned that this didn't mean that every population of frogs was going to be affected. But at times it almost seemed that would be the case. Over the course of the season, the MPCA received 190 reports of deformed frogs--the majority were sightings of multiple abnormal animals--from citizens as well as officials at other government agencies.
The MPCA staggered under the crush of new findings. Helgen and her staff scrambled to investigate as many sightings as possible. They managed to confirm twenty-one sites with deformed animals in fourteen counties, from shallow, vernal wetlands in the southern corn belt to the sprawling marshes and lakes of the far north. The MPCA collected almost 3,000 juvenile leopard frogs over the summer. Just under 12 percent of the animals were deformed--although the incidence of deformities varied considerably from site to site and from one visit to the next. Some trips to affected sites turned up nothing but normal animals; other times there were double-digit percentages of abnormal ones. On July 25, only one out of 117 leopard frogs caught at the Ney farm was deformed. By September 30, 46 percent of the animals caught at Ney were abnormal. At Audre Kramer's pond, just the reverse held. In July the rate of deformities was 65 percent. That fell to 36 percent in August and then to only 20 percent by early October.
Gleaning meaningful interpretations from this kind of data was close to impossible. The variables inherent in collecting frogs were so large that it was uncertain whether the trends were real or only apparent. Weather conditions, the skill and experience of the field collectors, and just plain luck all figured in how many frogs were caught and from which part of a wetland. These were factors that could shift dramatically in a single day at one site. But most sites were sampled once or at most a few times over the course of several months.
Even at that rate, what did the results of any of those collections actually indicate? Some animals were kept. Some were released after being examined. Few were marked so as to be recognized in subsequent collections. Maybe the same animals were being counted over and over again. The researchers also speculated that frogs crippled by limb deformities were easier to catch than the normal ones. After all, what was a field biologist but another kind of predator? Increased ease of capture would skew the ratios--though nobody had any idea how much.
But one observation held up consistently everywhere throughout the summer: Nobody found deformed adult frogs. All of the abnormalities were seen in young of the year--frogs that had just metamorphosed. Presumably, none of the deformed frogs seen in 1995 had survived. This wasn't altogether surprising--Helgen and McKinnell had duly noted the impact of the deformities on the frogs' locomotion. They fully expected that few of the frogs would be able to adequately feed and escape predators. Obviously, deformed animals must be dying off even as the scientists were trying to count them. So all that turned up in the data were the survivors. Who knew how many deformed frogs didn't live long enough to be counted?
Finally, the researchers had to consider the possibility that they were tracking only the most visible manifestation of a more complex syndrome, one that could have other, far-reaching systemic impacts on the animal. It was unknown whether the deformed amphibians had normal immune or nervous systems, or whether other organs were functioning properly, or whether they were diseased, or if there might be other internal structural deformities in addition to the malformed limbs. For that matter, no one could even say with certainty that frogs this year or the year before that looked normal really were normal. Perhaps not coincidentally, the MPCA had received three reports of declining frog populations that summer. The abundance of juvenile frogs at most of the sites the agency sampled suggested a relatively successful breeding season, but there was no long-term baseline data for comparison, so nobody could really say what impact the deformities might be having on local populations. Intuitively, it seemed unlikely that any wetland where a large percentage of offspring did not survive their first year could sustain normal population levels over time.
McKinnell began getting disturbing answers to some of these questions as soon as he started dissecting deformed frogs that summer. Because of his long experience in examining frogs for tumors, McKinnell had been assigned to perform necropsies in order to look for internal abnormalities. He expected to find some. Frogs with external limb malformations, he maintained, would be "remarkable if they were bereft of internal pathology."
McKinnell dissected more than five hundred frogs--including both normal and abnormal appearing ones--that were collected during the summer of 1996. And, just as he suspected, there were internal problems.
There was evidence of abnormal reproductive system development--a finding consistent with exposure to some external toxicant. Chemical agents that cause developmental abnormalities are called teratogens. Teratogens can impact many organ systems and body structures, but sex organs are a favorite target. McKinnell found testes that were dramatically undersized in male frogs, and because some were also virtually clear instead of opaque, as they normally are, he noted that in many cases they were hard to find even under the dissecting microscope.
Other abnormalities were found in digestive tracts. The most dramatic ones involved the stomach and lower gut, which in some of the animals were severely distended and stretched. McKinnell was astonished to see repeated instances in which the gut wall had become almost totally transparent, so that its contents were readily visible. Even the gut contents were unusual. Many of the frogs were literally full of undigested insects and insect parts. McKinnell also found undigested insect pieces in a number of bladders--an observation he found utterly incomprehensible until he determined that it was directly related to the swollen guts. The only explanation for what he was seeing, McKinnell realized, was that the frogs were unable to digest what they were eating. As more and more undigested food ballooned the gut, the frog could not expel this material. Frogs have only a single opening at the rear, a vent called the cloaca that provides a common outlet for urine, feces, sperm, and eggs. As undigested food blocked t he cloaca, it began to back up and ultimately regressed into the bladder. McKinnell determined that despite being crammed to the bursting point with food, even the frogs with enough mobility to feed themselves were starving to death.
And there was one more thing. McKinnell knew that leopard frogs will only eat live food. They won't consume anything that doesn't move. Yet mixed in with the undigested insects, McKinnell also found small sticks, leaves, and even pebbles in a number of frog guts. While McKinnell conceded that he was at a loss as to what might explain this strange finding, he marked it down as potential evidence of a behavioral abnormality--something new to go along with the physical malformations.
Meanwhile, McKinnell and his assistants continued to marvel at the various physical abnormalities exhibited by frogs brought in from the field. Probably the best known, because Judy Helgen posted a photograph of it on the Internet, was one with a thin, pink, perfectly matched pair of extra legs growing out from between its normal hind legs. Another favorite was a leopard frog that had a very uncommon forelimb deformity--a well-developed extra leg that protruded from just behind the corner of frog's right jaw.
In late May of 1996, David Hoppe returned to the Bocks' lake, wondering all the way there if he'd find anything like what Dennis and Rhonda had described to him the previous fall. He arrived about ten o'clock in the morning and immediately heard frogs calling--not the earnest, heated chorus you'd expect to hear in the evening, but just the steady thrum of a lake alive with frogs. As he had anticipated after his first visit, Hoppe discovered a number of frog species in residence, including several that only an experienced field herpetologist would readily find. Listening carefully, Hoppe could hear several leopard frogs calling, plus a slightly larger contingent of American toads. Toads have one of the most delightful of all frog calls--a musical, high-pitched trill that at the height of the breeding season fills the summer night like nothing else. Hoppe was encouraged by the apparent abundance. Making his way down to the shore he heard a gray tree frog calling.
Hoppe waded into the reeds, edging through floating mats of vegetation. The air was heavy and close. The lake had a ripe, organic odor. Buzzing squadrons of insects swirled around him and oscillating shafts of sunlight angled through the leaves of the trees that hung out over the water. Hoppe moved carefully. It was slow, sweaty going. The bottom was a heavy muck, difficult but manageable for wading. Inside the vegetation line the water was only thigh-deep. He made his way slowly up the shore, pulling one foot out of the mud as the other sank in, inching his way toward the fence running down the bank and into the water at the edge of the property a hundred yards or so north of the dock.
The shoreline looked like frog heaven and it was. There were many frogs and a great many more large tadpoles submarining through the brown water as Hoppe pushed ahead. He caught sixteen adult frogs and two subadults, gently returning them to the water after a close inspection. They all looked fine. The lake seemed almost crowded with robust, healthy, normal amphibians.
Hoppe made a total of seven visits to Bocks' lake that summer. On land, he captured spring peepers, wood frogs, gray tree frogs, American toads. At the water's edge he netted leopard frogs. His major find was in the lake itself. Wading the shallows, he caught mink frogs, a highly aquatic species that immediately confirmed the lake was both a breeding and an overwintering site.
Adult mink frogs spend most of their time in the water, rarely venturing more than one or two jumps onto dry land. They are also slow developers. Unlike other frogs that metamorphose just weeks after hatching and can migrate from their breeding ponds, mink frogs typically spend one full year in the larval stage and pass their first winter as tadpoles in the same place they hatched. Mink frogs are attractive, sturdy animals--a tad smaller through the body than leopard frogs. They're a dark, mottled green in color, usually with a bright green chin.
Mink frogs get their name from their musky odor, which is more pronounced in adults. Although kids playing by lakes sometimes come across mink frogs, they are not nearly so commonly seen as other species. Hanging motionless in the water, with only their eyes and nostrils above the surface, or hunkered down in a tangle of aquatic vegetation, they can be almost impossible to spot from only a few feet away. Dennis and Rhonda said later that they were completely unaware of the mink frogs living in untold numbers just a few feet from their shoreline.
Hoppe had been initially excited by the extravagant numbers and the rich diversity of frogs he encountered. It was hard to believe there could be anything seriously wrong with the environment here. But if the deformities Dennis and Rhonda said they'd seen the year before were present again this year, Hoppe felt certain that whatever caused the abnormalities would be found in the lake, which seemed like it must be center stage for all of the frog species in the area. Hoppe stepped up his pace as the weather warmed, visiting the lake as often as he could during the peak of metamorphosis in order to see as many of the new crop of juvenile frogs as possible.
He was not prepared for what he found.
The scene at the Bocks' lake deteriorated in front of Hoppe's eyes. By midsummer the lake had become a watery nightmare. Each successive collection revealed a fresh perversion of nature. The frogs reproducing along the Bocks' shoreline--where the family had swum and caught their Sunday supper for years, and where Hoppe had seen nothing out of the ordinary only weeks before--were being ravaged. There were significant levels of deformity in every species. The most severe abnormalities--the worst yet seen anywhere in Minnesota--occurred among the mink frogs.
The mink frogs at the Bocks' lake exhibited every type of deformity previously seen at other places in the state--plus a ghastly parade of new ones. Some were missing legs or leg parts, but most of the animals had some sort of twisted addition to their normal complement of limbs. Many had the strange skin webbings--Hoppe started calling them "cutaneous fusions"--that spanned the trailing edges of the hind legs, preventing their full extension and in the most extreme cases totally immobilizing the limbs. Hoppe found it hard to look at these animals and not wonder if they weren't likely to die by drowning.
Other frogs had stumps of legs or partly formed limbs protruding at odd angles from their hindquarters. There were legs that split, branching off in two or more directions, as well as legs that had extra feet, and feet that had extra toes. There were tapering, leglike appendages sticking out from the rear flank like wings on an airplane. One frog had a total of nine legs. Others were so badly deformed that Hoppe could not describe them in his field notes, or ran out of room trying. He took one of the worst cases--a mink frog with a confused tangle of hind limbs bunched in a fleshy mass and festooned with extra feet and toes too numerous to count--back to his lab in Morris. His students nicknamed the frog "Scrunch." Despite the most attentive care and regular hand-feeding, Scrunch died after about ten days in captivity.
As the summer deepened, Hoppe became convinced that the occurrence of such profound deformities and the presence of so many different species would provide new insights into what was happening. Hoppe had by then visited the Ney farm down in Henderson and had found a few toads with deformities, but the wide spectrum of species affected at the Bocks' lake was arresting.
All of the frogs here showed a range of limb abnormalities, though in general none seemed nearly so bad off as the mink frogs. What interested Hoppe were the varying incidences of deformities among the different species. Fully half of the mink frogs were deformed. About 10 percent of the leopard frogs were deformed. Among the wood frogs, spring peepers, gray tree frogs, and American toads the abnormalities occurred on average in only about 3 percent of the specimens he inspected--although this was still more than Hoppe had ever seen anywhere in all his years of field collecting.
Hoppe saw that if he arranged the frogs in order of their affinity for the water that the rates of deformity corresponded perfectly. The more aquatic the species, the higher the incidence of abnormalities. Surely this was yet more proof that a waterborne agent was implicated in the deformities. Or was it? The fact that adult mink frogs spend a lot of time in the water would help explain that species' higher susceptibility to deformities only if the malformations were the result of parental exposure to a toxicant in the lake--something that bioaccumulated in the tissues of the mother and was then passed on inside her eggs as a birth defect.
If the deformities did not result from such a maternal transfer--if they were developmental errors induced after conception--then the picture was murkier because there were fewer behavioral differences among the species. All of the frogs were in the water in the egg stage. And, of course, all were completely aquatic as tadpoles. They were immersed in the water throughout their development. On the other hand, they reproduced at different times and that could mean different exposures to a toxicant that was present in varying concentrations over the course of the season. In the end, though, Hoppe could not ignore the fact that mink frogs would endure a much longer exposure to anything in the water simply because they remained tadpoles throughout their first year.
Hoppe asked Dennis and Rhonda if he could invite the MPCA up to take samples and see the the appalling array of deformities in the lake. They agreed. Dennis recalled later that they had decided they trusted Hoppe and that they would do whatever he recommended. They also got a visit from Bob McKinnell, who accompanied Hoppe one day. Dennis remembers asking McKinnell if he thought they should stop swimming in the lake. McKinnell said that looking at it objectively, he doubted very much that there was any risk in just going in the water. But he said he wouldn't do it.
"That kind of made an impression that stuck with us," Dennis told me. The Bocks stopped swimming in the lake.
Posted November 17, 2001
I had to read this book for science. I'm not very, very interested in the topic, but the book was pretty good. For someone who likes science, I recommend it. It gives you enough information, though, if you know nothing about the deformed situation. The beginning is good...it gets a little boring as it gets to chapters 4, 5, and 6. When I say boring, I mean that it's very non-fiction-like...I don't usually like that. But it isn't a half bad book.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.