A spring peeper is a tiny frog, barely bigger than your thumb, famous for making one of the loudest sounds in nature relative to its size. These little brown frogs live in forests and wetlands across eastern North America, and they get their name from the high-pitched peeping calls the males make in early spring.

When winter ends and the ice melts, male spring peepers gather in shrubs and grasses near ponds and start calling to attract females. Each frog makes a single, clear peep sound, but when hundreds of them call together at dusk, they create a deafening chorus that can be heard a mile away. Many people consider this cheerful racket the true sound of spring arriving.

Despite being so loud, spring peepers are incredibly hard to spot. They're only about an inch long, roughly the size of a quarter, with sticky toe pads that help them climb. They have an X-shaped mark on their backs that helps identify them, if you can find one. During the day and through most of the year, they hide under leaves and logs, completely silent. But on those first warm spring evenings, their persistent peeping announces that winter is finally over.