Tiny mites give some Central American poison frogs most of their toxic sting, researchers have discovered.

Many tropical frog species secrete compounds known as alkaloids to protect themselves from predators and prevent infections.

Scientists knew that frogs don't produce the toxic compounds themselves, but rather acquire them from their diet. For instance, poison frogs raised on a diet of fruit flies—which contain no alkaloids—quickly lose their dangerous slime. (Related: "Poison Frogs Losing Their Toxicity, Study Suggests" [November 7, 2006].)

But until recently, said Ralph Saporito of Florida International University (FIU) in Miami, "it's been a mystery what the dietary sources are."

Ants are known alkaloid producers, so previously they had been assumed to be the major source of the more than 800 known alkaloid compounds present in poison frogs.