Welcome Wood Frogs!
By Sarah Breznen, Director of Education - March 2018
Soon you may begin to hear what sounds like ducks cackling in the woods. But that cacophonous quack does not come from a bird. What you are hearing is the chorus of wood frogs!
Wood frogs are one of the earliest amphibians to emerge from hibernation. They awake in March, sometimes as early as February, when the temperature remains warmer for several days and begin to gather in vernal pools and wetlands to mate. Wood frogs are incredibly cold tolerant and can be found in pools when there is still ice present.
They spend the winter under logs and leaf litter. Unlike other animals that hunker down below the frost line, wood frogs bury themselves only a few inches below the surface. These amazing little creatures can freeze themselves into an icicle and survive! Their hearts stop beating, they stop breathing, and 60% of their body is frozen solid. Most animals cannot survive being frozen because ice crystals will damage cell membranes and tissue. However, wood frogs produce something like antifreeze (high concentrations of glucose) that protect and prevent the cells from freezing. Ice forms around the organs and cells but not within them to cause damage. Wood frogs can endure cycles of freezing and thawing due to this adaption, however, they can die from a sudden cold spell or frost that does not give them enough time to find shelter. Scientists are studying wood frogs freezing and thawing and looking at the application to humans and improving organ transplants.
Wood frogs are small, with a dark brown eye mask. They are typically brown and tan (sometimes rustcolored) which allows them fantastic camouflage amongst the dried leaves of the forest floor. Wood frogs spend most of their adult lives in the woods, migrating in masses to vernal pools to mate in early Spring and then returning to the forest. Adults feed on insects, slugs, and earthworms. The tadpoles feed on aquatic vegetation and leaf material in the pools.
Frogs are important indicators of the environment. They have permeable skin and eggs that can easily absorb toxic substances from the environment. If there are many frog species in an area, that can be a good sign of a healthy environment. As the weather warms, keep your ears out for these amazing amphibians!