Winter Survival Series: Frogs and Toads
Posted on Thursday November 7, 2019
Ever wonder how a tiny frog is able to survive the harsh winters they must endure year after year in this part of the world? There are different ways that frogs survive sub-zero temperatures and the method they use is usually related to the habitat the frog uses.
True frog species, such as Bullfrogs, Green Frogs, and Leopard Frogs are primarily found near permanent waterbodies such as wetlands, rivers, and lakes. These frogs tend to overwinter by burying themselves in leaf litter or hiding in rock or log crevices at the bottom of waterbodies that will not freeze solid. Their ability to breathe through their skin, like all amphibians, ensures they can obtain the oxygen they need to survive while overwintering under water. As cold-blooded animals, their body temperature will be the same as the cold water they overwinter in, which will substantially slow down their metabolism and allow them to survive the winter without the need to eat.
Toads are more terrestrial and actually burrow into the soil below the frost line to avoid freezing during the winter. They too will slow their metabolism and go into somewhat of a “sleep mode” until the soil warms up enough to cue their re-emergence the following spring.
The Wood Frog, as well as all of Ontario’s tree frog species, don’t live near permanent bodies of water and cannot dig into soil, so they have adopted a more interesting method of surviving our harsh winters. These frogs have evolved to safely freeze once temperatures drop below zero. Imagine that! When normal cells freeze, ice crystal form inside the cells. These expanding ice crystals cause the cell walls to burst open resulting in irreversible damage. These freeze-tolerant frogs however, actually produce an antifreeze substance that prevents their tissues from rupturing and allows much of their cells to freeze without causing any permanent damage. A partially frozen frog will stop breathing and its heart will stop beating. Upon thawing, its lungs and heart will simply kick back into action, and the frog continues with its life processes of searching for a mate and food the next spring.