.[Reprint from February 2011]
My mole Tboy (mole as in spy, not insectivore) tells me Valentine’s Day has its intended effect on the wood frog population in southwestern Virginia. Mid-February is when the first early-bird males usually appeared at area ponds, floating patiently in anticipation. Within a few days the gene pool is getting crowded, and the boys are warming up for karaoke and the start of happy hour. Once the ladies arrive and joint be jumpin’!
The watering holes have been silent for the last few months. Winter is a time for amphibians to lie low. Really low. Aquatic frogs hibernate on or partially submerge in the mud at the bottom of ponds and lakes. Terrestrial frogs, including the wood frog, hibernate on land. Some burrow down below the frost line, but wood frogs are not adept diggers so they seek out crevices in rocks, crawl beneath a log, or just huddle in the leaf litter. Their hibernacula don’t always make for cozy inglenooks. When the temperatures drop below freezing, so do the wood frogs. But not to worry—wood frogs have what it takes to best Old Man Winter.
No, I’m not talking about well drinks. A high concentration of glucose keeps a frog’s vital organs from freezing, so even though the animal may stop breathing and doesn’t have a heartbeat, it’s not dead. As soon as things heat up again, the frog thaws and life goes on.
The wood frog club scene is cool. That’s because it usually begins in late winter, sometimes before the ice has disappeared from vernal reproduction pools. The whole rave lasts for about two weeks. A female steps onto the dance floor—I mean into the water—and a male grabs her and holds on tight. The process is called amplexis. That’s Latin for embrace. Yeah… kind of like the way sumo wrestlers embrace. Because once the male has her in his arms, he’s not letting go without a lot of… persuasion. Sometimes not even then.
The process is highly competitive and not without hazards. “Satellite” males hang out beyond the water’s edge so they can grab a gal while she’s in transit. In this way, he avoids jostling with the boys at the pool while also scoring a ride to the party. Male wood frogs are stimulated by movement so they;re not always discriminating about who they grab. Sometimes it’s the wrong species of frog, and sometimes several males will grab the same female, which can cause her to be squeezed to death or drown. Club life has its ugly side, too.
But, assuming there aren’t any bar brawls, the female will lay large masses of 1500+ eggs, choosing a site where they receive sunlight and protection from predators. When she releases her eggs, the male—who has been waiting for this opportunity and is now in the perfect position—fertilizes them with a sperm-containing fluid and soon the eggs begin to develop.
Eventually, the tadpoles hatch and begin their metamorphosis, absorbing the nutrient reserves in their tails to fuel their makeover.Time to head for the forest and get on with the serious business of making a living. Last call! (Until next year, that is).
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© 2011 Next-Door Nature— no reprints without written permission from the author. Cover photo by Garrett and Kitty Wilkin; egg mass photo by Richard Bonnett; metamorphose photos by Brian Gatwicke. Thanks to all these photographers for making their photos available for use under a Creative Commons license.