The wood frog has a large North American range (Photo: Garrett and Kitty Wilkin, Creative Commons license)
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[NOTE: It's been such a mild winter this year that I've been hearing wood frogs and spring peepers singing through my open window for several weeks now. In honor of their evening serenade, and to buy myself some time to take care of blog-maintenance duties, I decided to update and re-run a favorite post from early in the NDN repertoire. Enjoy!]
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My mole (that’s spy, not insectivore) Tboy tells me Valentine’s Day has had its intended effect on the wood frog population in southwestern Virginia. The calendar had barely flipped over to February when 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—male is on top
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 sumo wrestlers hug. Because once the male has her in his arms, he’s not letting go without a lot of… persuasion. Sometimes not even then.
Froggy courtin’ 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. Thing is, 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.
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).
Your wood frog looks a little like our cane toad, but better looking! Our cane toad has lumps and bumps on his skin and poison glands behind his head!
You have written a fascinating post about the wood frog, thank you so much for an interesting read.
I love the analogy to a club. I used to describe the return of the California newts to their ponds as a “newt party.” It’s difficult not to draw those comparisons when you witness the phenomena. That being said, I’ve never seen a Wood Frog … but would like to. Especially now that I know about their secret raves.
Wood frog raves are the best time to see them, because once the party’s over everyone goes their separate ways and individual frogs are harder to discover. Besides, when things get loud down at the watering hole it’s easy to find the hop spot!
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