Tuesday, February 25, 2014

Native Species Spotlight: Lithobates sylvaticus | Wood Frog

An amazing photo of a female Wood Frog by my new friend, Lisa Powers. Females are generally reddish in color, particularly during their breeding season.
One of the first signs of spring — or at least the ones I look for — are the Wood Frogs. Where I am from in Massachusetts, Wood Frogs brave the ice and snow to make it to their vernal ponds to breed every year. I can recall many times when I am out at night in the spring—freezing! ... and these little frogs aren't complaining (and they can't even produce their own body heat!) — they are just making their way to the breeding site. In Georgia, the Wood Frogs are out right now, calling and laying eggs in ephemeral pools (and occasionally the edges of permanent wetlands)
Wood Frogs typically lay all their eggs in one place, so if you find one clutch, you have probably found them all. When laid, they are about the size and shape of a tennis ball or baseball, but quickly swell up with water and become much larger. Here is a video of some eggs I found last week in Dekalb County.


At night, Wood Frogs can be easily identified by their call — which sounds like a bunch of ducks. Just remember that ducks don't quack at night, so if you hear them they are most likely Wood Frogs.

Here is a fantastic video of developing Wood Frog eggs filmed and produced by Tracy Hicks. The way he adjusted the lighting makes it possible to see the embryos with much greater definition. Thanks Tracy for sharing this with us!
Wood Frogs in amplexus at the edge of an ephemeral wetland. Males are smaller and browner in color in contrast to the females. Thanks to Lisa Powers for sharing her images with us! These were taken just a week or so ago.
Wood Frogs are easily spotted for 2-3 weeks a year, so get out there soon if you would like to see one.
Did you know?
Wood Frogs can freeze solid during the winter? These freeze-tolerant or cold hardy frogs have the ability to detect when the cold weather is coming and can regulate the amount of inter-cellular fluid. By reducing the amount of water inside their cells, it increases the salinity inside the cell. This allows the extra-cellular spaces to freeze, while keeping the actual cells in tact. When spring comes, the frogs simply thaw out. When I was doing my first field experiments in Massachusetts, I was digging in a drift fence and accidentally uncovered a frozen Wood Frog! As I held the frog it 'came back to life' right in my hands. These are incredible animals and we have them right in our own backyards.
For more information on what these and other 'cold blooded' (poikilothermic) animals do in the winter, check out this lecture on Freeze Tolerance and Supercooling.