The song of the lowland coquí rings throughout Puerto Rico, from late afternoon when the first pre-dinner cocktail is shaken at the El San Juan hotel until the last margarita glass is salted past midnight.

But the chorus of ko-kee chirps from the dime-size amphibian is getting quieter in recent years: The species is declining due to the island's development boom.

Now listed as endangered by the U.S. Fish and Wildlife Service, the butternut squash-colored frog only lives in one freshwater wetland. It also breeds on just one type of plant, the bulltongue arrowhead. (Read about how frogs are disappearing worldwide.)

But lately, the lowland coquí has an unexpected safeguard: The Puerto Rican debt crisis, which has halted