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For a biology professor to watch more than 200,000 wood frog tadpoles die is bad enough — but to watch them die in his own backyard pond? Within just one day? "It was like a nuclear detonation," Bowdoin College's Nat Wheelwright told NBC News. What caused last year's mass die-off at Wheelwright's home in Brunswick, Maine? In a study published by Herpetological Review, he and researchers from the University of Tennessee say the culprit was probably an insidious type of virus.

Ranaviruses are among the factors implicated in the global decline of amphibians, and this would rank among the biggest and most sudden such die-offs ever seen in Maine. The tadpoles were wiped out during their metamorphosis to full froghood. Adult frogs living around the pond were unaffected, but the wipeout doesn't bode well for Wheelwright's pond. "I'm afraid to say it appears that this year's cohort is also gone," he said. The die-off could well extend farther. Citizen scientists can help by participating in frog-watching efforts such as the Maine Amphibian Monitoring Program.

In addition to Wheelwright, the authors of "Sudden Mass Die-Off of a Large Population of Wood Frog (Lithobates Sylvaticus) Tadpoles in Maine, USA, Likely Due to Ranavirus" include Matthew Gray, Rachel Hill and Debra Miller.



— Alan Boyle, NBC News