During winters in North America, many amphibians dive or burrow deep to avoid freezing—but not the wood frog. These fig-size croakers stay put above ground as the water between their cells freezes, and they spend the season in a kind of cryosleep. When spring arrives, most wood frogs awaken from their icy slumber with one thing on their mind: sex. Males find a pond and call to females with sounds “almost like a quacking duck,” says Dartmouth College biologist Ryan Calsbeek. As more males join in, the cacophony of croaks can be heard throughout the forest. Hearing the come-ons from the ponds around them, females hop toward the croaks they find most seductive. In a recent study … Calsbeek determined that female wood frogs can’t resist deep, husky voices. Such croaks tend to come from large frogs—but once lured to a pond, she’s fair game for all its male frogs, including small sopranos.