At the end of winter, just when you are thinking spring will never arrive, an ancient amphibian ritual begins to reassure us that spring is finally here. Wood frogs are an amazing amphibian that are found throughout the Washington DC area, the eastern United States, and most of Canada and Alaska all the way to the Arctic Circle.
To witness this froggie ritual, head outdoors as the days are reaching the 60 degree mark and the nights are rainy. There will be about a 2 week window when millions of adult wood frogs emerge from hibernation to sing and mate. You just need to take a walk into a wooded area where there are puddles of water, also know as vernal pools. These special pools dry up in most summers and fish are not able to live in them, so they are perfect for variety of amphibians to lay their eggs.
Male wood frog songs sound a bit like a quacking duck. As you approach a wood frog filled pool, their songs may stop, but if you sit or stand quietly, they will begin again. And it is amazing. Some pools may have hundreds of frogs right in front of you! During daytime, you will mostly see males. At dusk and nighttime, the more secretive females become active and available for all the males to court.
In just a few days, millions of gelatinous eggs will be laid by the female wood frogs. The eggs will hatch into tadpoles in about 1-4 weeks, depending on the weather and water temperature. The tadpoles will go through metamorphosis lasting about 2 months and then hop out of the pool as teeny frog-lets. The frog-lets disperse into the surrounding woodlands to feed on tiny insects and hide from predators. If they survive, they will return to the same pools as adults to repeat the cycle.
These small to medium sized, leaf colored frogs spend most of the winter buried under ground or at the bottom of vernal pools where they may actually freeze solid. It is this amazing freezing ability that has many scientists so intrigued.
Frogs are vertebrate animals. Just like people, they have muscles, bones, blood, and all the same internal organs (heart, liver, kidneys, etc…) too. This is why so many high school biology students dissect frogs, not to learn frog anatomy, but to learn human anatomy.
Wood frog anatomy is very similar to humans, just like other frogs. However, wood frogs have a very special physiology. Wood frog physiology allows ice crystals to form in their cells without rupturing the cell walls, as would happen in other vertebrate animals. And even more amazing, when they defrost, their bodies defrost from the inside to the outside!
Scientists are studying wood frogs to learn this secret and possibly figure out how to apply this ability to humans. Imagine if we could freeze humans, keep them in frozen hibernation during long space voyages, and then defrost the space-goers with no ill effects from the freezing. Kind of like Han Solo in The Empire Strikes Back!
Wood frogs are toadally wonderful!