Fungus Pushes Frogs Toward Extinction

Posted by erauch, August 3, 2011

It’s been called a crisis in amphibian biology: more than a third of amphibian species are at risk of extinction. Habitat loss and climate change are both causes, but so is an invasive disease that’s been called the smallpox of the amphibian world. Researchers from D.C., Virginia, and Maryland recently traveled to Panama to try to help limit the effects of the disease.

Combing the rainforest in search of frogs

It’s the middle of the night, and the middle of the rainforest in Central Panama. A group of researchers is slogging through a stream. It’s dark, and dozens of critters are watching — just not the ones they’re looking for.

“I can see the eyes glowing right there; it’s probably just a spider,” says one of the researchers, Brian Gratwick.

Gratwicke usually lives in D.C. He’s a biologist with the Smithsonian’s National Zoo. But right now, he’s here looking for frogs. And nobody’s having much luck.

“We’re looking for little green blobs sitting on a green leaf; anything that makes the leaf hang unusually,” says Brian Gratwicke.

They’ve been at it — looking for this frog — for more than an hour and a half. They’ve seen plenty of giant spiders and venomous snakes, not to mention a very large lizard — but no frog.

Finally, success: a glass frog guarding a gelatinous pile of eggs.

“See those tadpoles wiggling inside the eggs?” Gratwicke says. “Right above the stomach, you’ll see a teeny white thing that’s beating, and that’s his heart – see his heart beating?”

It’s called a glass frog for a reason: its skin is transparent.

It might’ve just been a bad night, but researchers have documented glass frog population crashes of 80 percent at lowland sites like this. Tonight has been frustrating, and they call it a night.

Searching for the source of frog epidemic

For a long time it was a mystery what was causing such disappearances. For years, scientists watched extinctions and die-offs sweep across Central America. It was the National Zoo in D.C. that first characterized the culprit back in 1999: a fungus called chytrid. And the more researchers looked, the more they found it wasn’t just a problem here.

Humans have spread it around the globe, and it’s left a trail of amphibian die-offs and extinctions in its wake.


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