With an eye-patch like a bandit and bodies no bigger than 3 inches, wood frogs are among the fascinating critters that spend the winter sheltered in backyard and woodland leaf litter. If you find one that looks frozen, let it be.
Wood frogs’ ability to become winter frogsicles counts as their biological superpower. Their bodies create the equivalent of antifreeze that floods their system.
“It prevents damage from happening to the cells,” said Ken Kozak, curator of herpetology at the University of Minnesota’s Bell Museum of Natural History.
Wood frogs, as well as tree frogs, can shut down bodily functions, mostly freeze for the winter, and thaw in the spring. They are currently coming back to life across the state as hearts start pumping again and lungs return to breathing.
Brown, reddish-brown or almost black, wood frogs are often the first active amphibians in Minnesota, along with boreal chorus frogs. They can be found throughout the Twin Cities and northern Minnesota. Their ability to survive cold weather means they can be found as far north as the Arctic Circle.
It also means they’re getting busy mating before seasonal ice has finished melting. Breeding season can start as early as late March and run throughout April. Males inflate two vocal sacs to make sounds that resemble “racket racket racket” (a bit like garbled chicken or duck clucks) in their quest for a partner at ponds, lakeshores and seasonal pools.
Females lay 1,000 to 3,000 eggs, usually attached to a submerged plant. The early start helps assure that water won’t dry up in the three weeks the eggs need to hatch. It takes an additional six to nine weeks for young tadpoles to swim and grow until they’ve developed legs and lungs to survive on land. As they make that transition, skin grows over the gills they used as tadpoles.
Lisa Meyers McClintick has freelanced for the Minnesota Star Tribune since 2001 and volunteers as a Minnesota master naturalist.
