AILSA CHANG, HOST:
It's a case that went cold some 45 million years ago. What killed a couple hundred ancient frogs? NPR's Ari Daniel brings us a mystery that at long last may have been solved.
ARI DANIEL, BYLINE: Central Germany was once a coastal, subtropical swamp.
DANIEL FALK: With loads of creatures, loads of beasts running around.
DANIEL: Including - says Daniel Falk, a paleontology Ph.D. student at University College Cork - ancestral horses, giant crocodiles, huge snakes and plenty of frogs and toads. But in the modern era, things look rather different.
FALK: It's kind of like a fossil crime scene.
DANIEL: The swamp had preserved a couple hundred fossilized frogs and toads.
FALK: And the mysterious question is, like, why did all those animals die? Like, why did those frogs die?
DANIEL: For a long time, scientists thought the swamp had dried out, which could have killed the frogs. But Falk wasn't so sure.
FALK: I basically counted every single bone in every specimen.
DANIEL: The bones were in good shape, so the animals were healthy; there was even fossilized poop in a couple of them, so they didn't starve; and there weren't any predator marks, so the frogs and toads weren't eaten - process of elimination. And what was left, based on similar fossil deposits elsewhere and knowing about modern-day frogs, was that - and here's where it gets a bit gruesome - the ancient animals drowned while mating, especially the females.
FALK: And they sink down in the water. And if the females can't make it up to the surface at some stage, they unfortunately drown.
DANIEL: It's a theory Falk and his colleagues describe in a study published today in the journal "Papers in Palaeontology." If they're right, then it's not the males who revealed what happened; they're long gone. It's the females that have been preserved, whispering their story to us millions of years later. Transcript provided by NPR, Copyright NPR.