Frog Antifreeze

 Photo: © Scott Egan

Wood frogs in amplexus

Some frogs live high on mountain slopes or in the frigid North. During winter, a frog's body temperature falls and its metabolism drops; the heart may even stop beating. Many frogs dig into mud or deep holes to escape killing frost, but some practice controlled freezing. They produce excess sugars or starches to prevent damage to sensitive tissues while the remaining water in their bodies turns to ice. The North American wood frog can survive with 65 percent of the water in its body frozen!

The North American wood frog ranges well into the Alaskan tundra, inside the Arctic Circle.

Wood frogs are able to withstand sub-zero temperatures for extended periods during hibernation. They emerge early in the spring to breed in newly thawed pools and ditches.