While doing field work in Central America in the 1990's, biologist Karen Lips noticed the frogs she was studying were disappearing. Scientists in other parts of the world had documented the same thing - frogs and amphibians dying at an alarming rate. For years no one knew what was killing the animals until, finally, a bit of good luck helped solve the mystery. Follow host Maddie Sofia on Twitter @maddie_sofia. Email the show at shortwave@npr.org.