Wednesday, April 27, 2011

A Date With Cope's Grey Tree Frog

Last week's visit to "Highway Ponds WMA" in southern Maryland revealed a creature I have heard for many years, but never seen in the wild - Cope's Grey Treefrog.  I saw these two characters hanging out on top of a mining gate (4" galvanized pipe) and when they saw me, they ducked into the pipe immediately, making photography nearly impossible.  Since Copes' only differ in their genetics and their call, I based my identification of them on the fact that Copes' calls were filling up the woods on that cloudy, humid April afternoon. Wanna hear (I can't take credit for the video or audio)?

As their name suggests, tree frogs generally live in trees, but not necessarily adjacent to open water, where you'd find very closely related frogs like the Chorus Frog, Spring Peeper, and Cricket Frog.  However, in April and May, the Copes' and other tree frogs migrate down the trees and down the slopes toward large wetlands to mate and lay eggs.  I suspect that in areas (such as Southern Maryland, in the shadow of Washington DC, Baltimore, and Annapolis), high quality forested wetlands are a bit difficult to come by, and staking out one's territory this time of year might be difficult.  I think the result is my photo - two Cope's Grey Tree Frogs hanging out in a steel pipe. Their destination - the wetland below - seems like an admirable one.

But, as some astute (or regular) readers may note, I previously published this exact picture as an example of excellent shaded fish habitat to target in the mid-summer months.  That presents a problem for the tree frogs and for anyone seeking to manage them.  A frequent conflict I've had with landowners trying to manage wetlands involves my effort to keep fish out of places like this.   Why? Fish (notably bluegills and bass) are voracious predators of not only frogs, but also of tadpoles.  Predators - primarily fish, raccoons, and birds - can eliminate up to 95% of viable tadpoles and salamander larvae from shallow ponds.

In a landscape like the Adirondacks, this may not be a biological or genetic problem for frogs, since the landscape is covered with high quality wetlands, ponds, lakes and streams.  The predators can't be everywhere, all the time. Fish certainly can't access every bog in the entire region.  However, in a compromised landscape made up of farms, suburbs, and mining operations, the genetic stock of amphibians depends heavily on a pretty small number of created, restored, and managed ponds and wetlands to remain a viable population.  Fish can have a devastating effect on their success from year to year.  Please consider that the next time you consider stocking a "frog pond" or wetland with fish.  If there aren't fish in the pond already, the best thing you can do is to leave it without fish. Maybe you'll get a chance to have a date with a Cope's!


Map Monkey said...

I LOVE those little guys! Thanks for sharing your photos and story about them.

Jamie Cameron said...

The grey tree frog of eastern NC is my favorite amphibian. Always wanted to put my eyes on a Cope's that I was sure of. I need to check my range maps right now. Great post.

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