Now, species like the wood frogs, spring peepers, and grey tree frogs can thrive rather than survive, he said. Their mating calls now fill the airwaves day and night, the local officials said.

But frogs may yet hold clues to killing pain. At least one frog does deploy an opioid: the waxy monkey tree frog (Phyllomedusa sauvagii), whose skin is laced with the peptide dermorphin. Although the ...