by Don Scallen
Behold the wood frog, an evolutionary masterwork. A soft bodied amphibian that survives the fury of Canadian winters as far north as Old Crow in the Yukon. In that cruelest of seasons, wood frogs lie quiescent in beds of leaves, biding time until snowmelt softens their stiff bodies. They protect their delicate cellular machinery by shunting water out of their cells to freeze benignly in the spaces surrounding those cells. And as if that metabolic alchemy isn’t remarkable enough, wood frog cells become infused with glucose – enough, milligram for milligram, to kill a human many times over. For the wood frog though, this sweet syrup becomes a life-saving antifreeze.
Wood frogs are aptly named for they are utterly dependent on woodlands for survival. Essential, too, are ponds for breeding. Usually wood frogs choose ponds that hold water only temporarily – a roll of the dice that can lead to the death or salvation of their progeny. The absence of tadpole-chomping fish in a temporary pond explains the gamble. But, if the pond dries early, mass tadpole-cide will result. The prospect of drying ponds and limited life spans, force a particular urgency on wood frog sex. Of 52 weeks in the year they have but two or three available for reproduction in earliest spring. Moreover, wood frogs may have only one or two of these brief sexual opportunities before they end up in the gullet of a frog-hungry predator.
No wonder then, that a wood frog pond in April is a frenzy of activity. Males beckon females with quacking voices. They battle rivals – scrambling atop them and pushing them under water. Multiple males pursue lone females, in desperate attempts to couple. The mated females lay hundreds of black eggs that soon yield wriggling tadpoles.
The frenzied mating of the marvellously adapted wood frog has persisted for tens of thousands of years. Given woods and water, it should continue for thousands more.