Naturespeak A naturalist's view of the world

June 18, 2008

When is a Green Frog not a Green Frog?

Filed under: Uncategorized — wykes @ 5:25 pm

So, you’re walking along the shoreline next to a duckweed encrusted patch of water and you spot a frog. The beast is partly submerged but a significant portion of it is exposed above the water.  You can see it’s a big plain green frog. Let’s take this one step further and say you’d like to identify it. The size reference seems more important than the color observation given that a great number of our aquatic frogs are of the emerald persuasion, but actually the two facts are needed to narrow this thing down.  What I’m trying to say here is that our two largest native frogs are both green, but only one is a true Green Frog. Alright, I’ll explain.

   In the category of green frogs over 5 inches long, the Green Frog and the Bull Frog are the only two contenders. Sure, there might be a few huge Leopard Frogs out there droning Brando-like that they “coulda been-a contender” for consideration, but we are talking large green un-spotted frogs here.  If this walk had taken place somewhere in the Upper Peninsula, then the Mink Frog would need consideration. We are not in the da U.P. for this imaginary exercise in frog forensics, however, so let’s continue with the Green vs. Bull.

  How then, can the determination be made?  Green Frogs (like the example above) always have bright green upper lips and relatively pointy snouts whereas Bullfrogs have blunt snouts.  In a world of half submerged (or, optimistically half exposed!) frogs snouts are often hard to see, so one must get back to basics – the basics of the back.  It’s really just a matter of folds. Take a good close look at the exposed portion of the amphibian’s back. If there is a pair of ridges, or folds, running behind the eyes and down each side then you are looking at a green Green Frog (see here).  If there are no pinches or folds then the creature is a green Bullfrog (see here). Bullfrogs have a fold, but it curls tightly around the circular ear drum and ends at the chest. The rest of their body is an expanse of pebbly moist skin.

  There are many other ways to tell the two apart if need be, but there usually isn’t a need be. Should the green frog be the size of a honk’n huge lawn ornament, it has to be a bullfrog. Bulls get to be twice as large as Greens with snout to hind toe tip lengths of 12 inches or more. If the frog is on your plate, it has to be a Bullfrog. These are the only species locally used for frog legs.  If there is duckweed on your plate with the frog, then your frog is not dead and it could be either species.  If the frog has a fringed collar on, then it’s Kermit and he’ll explain how hard it is being green.     

  Should we allow the real frogs in question to speak up on this matter, the difference in voice quality will be very obvious.  The Bulls proclaim their masculinity with a deeply sonorous Barry White style “Jug-O-Rums” and the Greens plunk out a series of washtub bass “Klunks.” 

  Since we are sticking to visual clues for the time being, the folds are the factor.

1 Comment »

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