Froggy goes a-courtin’

wood frog

The wood frog has a large North American range (Photo: Garrett and Kitty Wilkin, Creative Commons license)

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My mole Tboy (that’s spy, not insectivore) tells me Valentine’s Day has had its intended effect on the wood frog population in southwestern Virginia. On February 18th the first early-bird male appeared at a nearby pond, floating patiently and quietly. Four days later, 50 guys had found their way to the gene pool and were warming up for karaoke and the start of happy hour. Any time now, the ladies will arrive and that joint be jumpin’!

The watering hole has been silent for the last few months. Winter is a time for amphibians to lie low. Really low. Aquatic frogs hibernate on or partially buried 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.  These hibernacula don’t always make for a cozy inglenook. 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.

Antifreeze.

No, I’m not talking about well drinks. A high concentration of glucose keeps the frog’s vital organs from freezing, so even though the animal stops 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.

wood frogs in amplexis

Wood frogs in amplexis—male is on top (Photo: Richard Bonnett, Creative Commons license)

The wood frog club scene is cool. That’s because it usually begins in January or February, 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.

wood frog egg massesThe 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. Also, male wood frogs are stimulated by movement so they’re not always discriminating about who they grab. Sometimes they grab the wrong species of frog, and sometimes several males will grab the same female. This can cause her to be squeezed to death or drown.

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.

wood frog metamorphosing

Eventually, the tadpoles hatch and begin their metamorphosis, absorbing the nutrient reserves in their tails to fuel their makeover.

wood frog metamorphosingTime 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. Egg mass photos by Richard Bonnett; metamorphose photos by Brian Gatwicke. Thanks to all the photographers featured in this post for making their photos available for use under a Creative Commons license.

2 thoughts on “Froggy goes a-courtin’

  1. I love frogs. Up here in Nova Scotia, Peepers arrive in late April and you can hear them by the hundreds for about three weeks.
    I also have bullfrogs around the pond and love to listen to them gossip in the early evening.

    walk in beauty.

  2. Pingback: Still life « Next-Door Nature

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