Boreal Frog (Photo Credit – Bryant Olsen)

In the spring I always welcome the croaks, peeps, and chirps of frogs and toads. As fall progresses toward winter, the songs fade. But where do the frogs and toads go? They are, after all, cold-blooded. Alaskan wood frogs actually freeze. No heartbeat. No blood flow. No movement. Nothing. As temperatures drop, their body flush with glucose produced in the liver, protecting the cells. It’s like having your own special antifreeze in your blood. In the spring the frogs thaw and hop away as if nothing’s happened, even though up to seven months may have passed!

Aquatic frogs drop to the bottom of their pond or other body of water. They don’t burrow in the mud though, they just hang out there to pass winter. Terrestrial frogs are a different story. These guys must burrow deep enough to get below the frost line or find cavities or crevices to squeeze into. This might include compost piles, in a beaver dam, in a mammal burrow, or in a gap between rocks. These frogs have the natural antifreeze, too, to help with extreme cold.

No matter the strategy, frogs and toads enter a state of torpor, a state of decreased activity when the heart rate and metabolism slow, and the body temperature drops. Among mammals this is called hibernation. But for frogs and toads, and other cold-blooded animals, this state is called brumation. Unlike hibernating mammals, amphibians and reptiles do not consume great amounts of calories to prepare for the winter. Their metabolism drops so low during the torpor that they cannot digest anything during this time. Brumation is triggered by cooler temperatures and fewer hours of daylight. Even in winter, these animals will move about on warmer days.