Grasonville, MarylandOn a warm evening in the spring of 2020, Jeremy Feinberg stood at the edge of a moonlit pond. He was on the Delmarva Peninsula, on the east side of Chesapeake Bay. “Chuck!” Feinberg called across the water. “Chuck! Chuck!” He cupped his hands behind his ears and swiveled back and forth, listening for a reply. Nothing. He called again. “Chuck! Chuck! Chuck!”

Feinberg is an ecologist. He was calling for frogs.

In the late 2000s, when Feinberg was studying southern leopard frogs for his Ph.D. at Rutgers University, in New Jersey, he discovered that the leopard frogs on Staten Island didn’t sound right. They looked like southern leopard frogs, but instead of the southern leopard frogs’ usual rolling chuckle, they had