Wild Tracks

On behalf of the world's wild species

Essential Frog Pee

Here’s a question you’ve no doubt pondered many times – are there frogs living in the Arctic?

Frogs after all, are amphibians who must have ponds, marshes or other bodies of water to survive. Water keeps their skin moist, and is essential for the development of the young. With temperatures plunging far below freezing in the winter, how could any amphibian survive?

Amazingly enough, there are frogs species in the Arctic that  survive by freezing solid in the winter, and reviving again each spring. Really.

Wood frog Rana sylvatica

Wood frog Rana sylvatica

Wood frogs Rana sylvatica are found throughout North America, and across northern Canada. They live further north than any other amphibian, and are the only frog living north of the Arctic Circle.

Known as a freeze-tolerant species, wood frogs can remain frozen at -3C for several weeks. Up to 65% of their body fluids freeze, and they are able to thaw and freeze repeatedly.

Scientists have long been curious how the frogs manage this feat without suffering the consequences of freezing. Researchers from Miami University have discovered that the frogs’ secret is apparently holding their pee.

Wood frogs gradually accumulate urea in response to a drop in water availability, and retain up to 25 times more in winter than in spring. Apparently urea, the main waste product in urine, works like anti-freeze, lowering the freezing point of any liquid. The body tissues may get slushy, but they never completely freeze, thus evading a major injury.

However bizarre the concept, ‘holding it in’ works well for the frogs. Wood frogs are a common species throughout the continent, and their population is currently in no danger. I spent much of my childhood playing with wood frogs and their tadpoles. While I do feel an affinity for these little guys, I’m not about to try holding my pee next winter to see if I feel warmer.


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