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NatureSpeak Articles

The amazing wood frog

After a very odd winter it’s finally spring and the animals will soon be getting ready to come out of their holes, dens and nests.

The animals of Whistler all have their ways to survive the winter – be it growing a longer coat, building a thick layer of fat, or storing food in their dens. Some of us also build up extra fat during the winter months. Hummingbirds, geese and many others animals head south for the winter and humans also follow this example and vacation south for a few months out of the year.

Yep. The golden rule of winter is if you freeze you die and try not to let this happen if you value life. But this is not true for all.

The wood frog, or Rana sylvatica, has evolved a very peculiar way of surviving winter. When the weather gets cold the wood frog hibernates in rocks, logs or among leaf litter. Yes, wood frogs don’t pick the warmest spots to hibernate. As the temperature plummets the wood frog’s heart beat starts to slow to a barely recordable rate .Nearly 1/3 of the frog’s body fluids become frozen but their cells are protected with a kind of antifreeze in their blood. They become, in a sense, frogsicles. A few other amphibians and some insects share this talent, but if you tried you would die of hypothermia.

As an animal freezes the crystallizing water pierces every cell thousands of times. Ever had frostbite? That’s what would be happening inside you if you were to get frostbite. It would be, in a sense, a deadly case of freezer burn. So for those of you who need to be told, don’t try freezing yourself. Remember the golden rule for winter, and putting real antifreeze in your blood just makes it worse.

But scientists are experimenting with freezing, and using the method of the wood frog they were able to freeze and revive a dog.

So what chemical allows wood frogs to achieve this? Well, it’s just glucose. High amounts slow down the freezing process but it doesn’t stop it. After the wood frog’s core temperature drops to about —7 it uses the snow around it as insulation, otherwise it would die.

Because of these adaptations the wood frog is very widely dispersed. Wood frogs live through out Alaska and almost all of Canada, ranging into the United States. Found in freshwater lakes, ponds, wet meadows, moist brush, slow moving streams and marshes, it is characterized by its prominent black "mask" extending from the tip of its snout through the eye to the ear. The Wood Frog reaches lengths up to 2.75 inches and they’re usually a shade of brown or green.

Wood frogs mate in the spring and have tadpoles, which may grow up to 5 cm long while feeding on algae and other plant material. Tadpoles take about two months to become adult frogs. In the meantime they have to look out for leaches, fish and aquatic insects. Adults, too, have a lot of predators, ranging from herons to racoons. Wood frogs are cannibalistic and will eat other frogs. It’s a frog eat frog world out there. Other than frogs Rana sylvatica eats insects, worms, snails, millipedes, molluscs, and other small invertebrates.

Because of the number of predators wood frogs live heart in mouth, have lightning fast reflexes and are notoriously hard to catch. In addition to speed an adult wood frog’s defences include producing skin secretions that deter predators, such as aquatic insects and shrews.

A remarkable animal with a remarkable ability to adapt, the wood frog is the only North American amphibian that occurs north of the Arctic Circle. You would probably find wood frogs in any of our local ponds, so this summer be sure to listen for the tell tale "quork, quork, quork" of the wood frog.

On those cold winter nights, try to compare yourself to the wood frog – frozen solid – and not the humming birds living it up in Mexico.

Lastly respect all our marshland habitat home of the wood frog.

Written by: Connor McGillion

Connor McGillion is a member of the Whistler Naturalists and currently a Grade 8 student attending Whistler Secondary School.


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