Fall masquerade

Natural History, Oct, 2005 by Erin Espelie

If spring in the Minnesota woods sings, autumn exhales softly. Take the inch-long spring peeper, Pseudacris crucifer, a chorus frog that lives among leaf litter and logs, near freshwater ponds. Its size and coloring make it easy to miss. The one pictured here didn't make a sound or move a muscle while under the sharp eye of photographer Art Wolfe.

Males start the spring by belting out a chorus of songs. But on finding a mate, they quickly quiet down (why advertise one's presence to predators?). Eggs hatch and tadpoles mature over the summer. When fall comes, the air can feel a bit like spring, and P. crucifer occasionally responds with a round peep; the effect is called the fall echo.

Winter is the real silencer. When cold weather sets in, the spring peeper hunkers down under the fallen leaves for a deep, solitary hibernation. Ice crystals start forming on the frog's skin and quickly work their way inside. The frog begins to churn out glucose from its liver, which will protect its cells from the deepening cold; its pulse slows, and its tissues continue to freeze. Finally the peeper's heart stops beating as it, too, solidifies.

Yet after the vernal thaw, the frog emerges no worse for the frigid wear. Its little body can still lighten or darken a few shades to match its surroundings. And it still has the strength for another mating rush--whose object is to be heard, but not seen.

Photograph by Art Wolfe