Peril in the Ponds: Deformed Frogs, Politics, and a Biologist's Quest

Epilogue: How Are the Frogs? An Update

{ 200 } EPILOGUE HOW ARE THE FROGS? AN UPDATE 7 More than a decade has passed since the MPCA halted its research on the frogs in 2001 and after my retirement in 2002 to compose the next chapter of my life teaching, writing, and spending time with family. Since then, major environmental disasters, such as the catastrophic BP oil spill in the Gulf and growing concerns about climate change have rightly dominated the news. Media coverage about frogs, on the other hand, has been almost nonexistent. Yet scientific reports from the first decade of the twenty-first century are disquieting : biologists report significant numbers of malformed frogs from sites across the country; male frogs have female egg structures growing inside their testes; and frog populations continue to decline both nationally and globally. In many areas the loss and degradation of natural wetlands continues. What does the future hold for frogs and the wetlands they need? Are we headed for another kind of silent spring, one with fewer frogs calling to attract mates? The Current Status of Frogs Globally, an astonishing one-third of amphibians (1,856 species) are classed as threatened with extinction. Among these, 427 species are listed as critically endangered, which means they are poised on the brink of extinction { 201 } HOW ARE THE FROGS? AN UPDATE worldwide. And a whopping 43 percent, or 2,468 species of amphibians, are experiencing some degree of population decline (Stuart et al. 2004; see update in Alford 2010). In spite of these troublesome facts, research on declining amphibians receives less support relative to that for work on threatened birds and mammals (Lawler 2006). Are frogs and salamanders not charismatic enough to merit more attention? Of less economic consequence? In the United States, twenty-three species of amphibians are classified as federally endangered or threatened, with eleven more waiting to be listed. Causes of these declines are multiple: habitat loss, diseases—particularly the deadly chytrid fungus that infects frog skin—and pollution present major threats. Invasive species and commercial exploitation also reduce amphibian populations (Alford 2010). The future for amphibians, both salamanders and frogs, appears bleak. Even the northern leopard frog (Rana pipiens, now named Lithobates pipiens) may be in jeopardy. At one of our study sites I remember the carpet of newly metamorphosed leopard frogs that covered the shoreline so thickly we had to wade into the water to avoid squashing them with our boots. We surveyed more than twenty thousand young leopard frogs during the course of the Minnesota frog investigation. They were everywhere, or so it seemed. Yet during the 1990s I heard stories from local people who no longer saw the mass migrations they’d experienced in their youth when frogs blanketed the roads near rivers. Harvests of leopard frogs in Minnesota to use as fish bait and for biological supply houses have continued, but records aren’t kept. Bob McKinnell and Dave Hoppe surveyed frogs in Minnesota from 1967 into the 1990s. Before 1975, they collected almost twice the number of frogs with body lengths exceeding 60 mm compared with more recent surveys. By the 1990s, frogs they collected were smaller overall. And “lunkers,” or frogs measuring 90 mm or more, were extremely rare (Hoppe and McKinnell 1997). “The frogs I’m seeing now are younger, they’re not living as long as they used to,” Bob told me. More recent reports about the once common leopard frog are troubling: extirpated in two-thirds of its historic locations in the western United States, they are declining dramatically in the provinces of British Columbia and Alberta in Canada (Wilson et al. 2008). They’ve disappeared from 95 percent of their historic range in California, and most have disappeared from the states of Washington and Oregon (Lannoo 2005). In eleven states the leopard frog is classed as “critically imperiled” or “imperiled.” That’s about a third of the states where it’s considered an endemic, or native, species. Populations are declining in Colorado, Indiana, Wisconsin . . . and the list goes on. I had no idea that the ordinary leopard frog was in such danger. How did this come { 202 } EPILOGUE about? I expected it would always be there, abundantly so. Small solace that in Minnesota Rana pipiens is considered “apparently secure.” Malformed Frogs Researchers have shown that abnormalities in frogs have definitely increased in frequency and severity in the past twenty years (Johnson et al...