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May 2, 2004
Outside Magazine
Outside magazine, September 1999

I hear that they've finally found out what's killing and deforming frogs—and that it's not our fault after all. True?

—William Trantor, Acton, Massachusetts

Frogs have been much in the press of late—and much on your minds, apparently—so we've decided to do an all-amphibian column this month. Almost everyone has heard the news that frogs are in trouble: Species around the globe have been suffering sharp population declines for almost three decades, and since 1995 there has been a marked increase in reports of deformities—cases involving multiple or missing limbs, cyclopia, and other assorted grotesqueries. Some herpetologists have suggested that these developments may reflect the low ebb of an as-yet-inscrutable population cycle, and one could optimistically argue that with close to 400 million years of evolution behind them, frogs are blessed with more than enough resilience and genetic variety to outlive these current travails. Still, because they inhabit both water and land and breathe through highly permeable skin, frogs are considered to be particularly susceptible to environmental change. Thus, the disappearing or deformed frog has emerged as a kind of environmental canary in a coal mine—possible evidence that we humans are wreaking untold havoc throughout the ecosphere. But this depressing scenario has now been challenged. In April, the journal Science published findings showing that a snailborne parasite called a trematode can cause certain frog deformities, and that a naturally occurring pathogenic fungus may be contributing to a large number of amphibian die-offs. Mystery solved? Not necessarily. Because the report purports to shed light on only a fraction of the malformations and declines, villains such as pesticide runoff, global warming, and loss of habitat are by no means off the hook. "The trematode has been around for millions of years, so either the parasite has become more virulent or the frog has become more vulnerable," notes David Wake of the University of California–Berkeley. "It's an intricate puzzle—proof that the simpler an answer seems, the more likely it is we've been deluded."


So what is the difference between a frog and a toad?

—Alison Bart, Lynchburg, Virginia

From the standpoint of anatomy, metabolism, and evolutionary lineage, frogs and toads are basically one and the same—all members of the multitudinous frog order Anura. (Despite their recent setbacks, there are still some 4,000 species of resourceful swimmers, hoppers, and croakers populating the planet.) The word "toad" is simply a bit of sloppy vernacular that we uninitiated observers have long used to describe those homely but likable members of the family Bufonidae, creatures that tend to have drier, wartier skin, squatter physiques, less pronounced foot-webbing, and a preference for terra firma. But even these basic differences have gaping exceptions. There are aquatic toads and land-loving frogs; there are warty frogs with dry hides and slimy toads with webbed feet. Not only are toads not toads, taxonomically speaking, some of them aren't even frogs: The horny toad, for example, is actually a lizard. "The whole frog–toad dichotomy is without scientific validity," insists Chuck Crumly, a researcher at the San Diego Natural History Museum. "It's artificial, it's slangy, and it's imprecise!"


How can frogs inhabit a puddle that only exists a few weeks a year? What happens when the puddle dries up?

—J. Morgan, Kansas City, Missouri

No, this is not a case of spontaneous generation. These mysterious amphibians—many of them desert-dwellers, such as the Mexican burrower—spend much of their lives in underground crevasses, where they wait in a zombielike state for what experts call "ephemeral pools" to form. When the rains come, the frogs are aroused by the moisture and lurch forth, desperate to procreate before the water disappears. Tadpoles hatch within a day and metamorphose into frogs in about two weeks. Though the majority won't survive the race against evaporation, those that do (some of them having resorted to cannibalism) will return to their burrows and wait until the next trysting lagoon is born.


Do frogs really rain from the skies?

—G. Spencer, Knoxville, Tennessee

However preposterous it may sound, this has been reported with greater frequency than you'd guess—all around the globe, and not just with frogs. In 1997 a Korean fisherman was knocked unconscious by a frozen lump of squid. And a Japanese vessel sank in 1990 after being clobbered by a falling cow. How does this happen? In most cases, the culprit is a waterspout or tornado that has sucked up the unsuspecting wildlife into the upper registers of a powerful storm cell—often freezing them before hurling them earthward with the rain, sometimes up to 20 miles away from where they started. Frogs and tadpoles seem to make especially good victims: small in size, but with enough wind resistance and heft to get airborne. Fortunately, such freak abductions don't always end in carnage. Take the pair of frogs that rained down on Iowa in 1882, encased in a hailstone: Eyewitnesses watched as the hardy amphibians hopped away—alive and well, if a little dazed from their ordeal.

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