“Coping” With the Heat, Treefrog Style

In the hill country of Texas where I live, it has been a pleasantly cool summer, thus far.  It has only recently begun to get hot and temperatures have only crept to the 100 degree mark in the last couple of weeks.  The rivers here are still quite high and most of the native Texans I speak frequently say how nice this summer has been.  It has been just the opposite in the Carolinas.  Columbia, SC, has already recorded 15 days of 100 degrees or higher this summer and, unfortunately, rainfall totals are below where they should be.

I spoke about the effect of the heat and lack of rainfall on Thompson Creek in my last installment of “Josh’s Jottings”.  The lower-than-normal water levels in the creek provided me the opportunity to study River Otter scat and, during my last visit to the farm, the heat had another beautiful creature “coping” with the high temperatures by hanging out close to the cooler areas around the creek.

A Cope's Grey Treefrog (Hyla chrysoscelis) rests in the notch of a Sweetgum (Liquidambar styraciflus) branch.

A Cope’s Gray Treefrog (Hyla chrysoscelis) rests in the notch of a Sweetgum (Liquidambar styraciflus) branch.  Well camouflaged, they can sometimes be tough to spot in the forest.

The most common treefrog (Family Hylidae) found on Southern 8ths Farm, by far, is the Cope’s Gray Treefrog (Hyla chrysoscelis).  I’ve heard their lovely trill almost every evening and night I’ve been at Southern 8ths Farm since May.  Occasionally, I hear them call in the wooded areas of the farm during the day; though they tend to do the majority of their singing once the sun has decided to slide below the horizon.  The call of this frog is often written off as background noise by most and, upon catching one during a nature walk I led a couple years ago, I had a lady tell me it was far from the prettiest thing she’d ever seen.  Regardless of what it may seem on the surface, like so many things at Southern 8ths Farm, the Cope’s Gray Treefrog is very interesting, indeed!

As we often do, let’s begin by looking at the names Cope’s Gray Treefrog and (Hyla chrysoscelis).  Edward Cope (1840-1897) was a gifted and famous American herpetologist from Philadelphia.  It is for him that this gray-colored tree frog is named.  The genus name is a reference to Hyla, the companion of Hercules, who was kidnapped by water nymphs at the spring Pegae, in Mysia.  As he was so beautiful, the naiad, Dryope. took him to forever to live in the waters of the river with her.  “Chryso” is the Greek word meaning gold and “kelis” is the Greek word for a stain or a spot.  Combining the two words gives us chrysoscelis, referencing both the metallic sparkling found in the granular skin of the frog and the bright orange coloration hidden on the inner thigh of the frog.  Cope’s Gray Treefrogs depend on their excellent camouflage to hide from predators.  If discovered; however, they will leap away at the last minute, displaying the flash of orange on the inside of their groin.  This flash of color often distracts the potential predator, allowing the frog to escape.

Like other frogs, the Cope’s Gray Treefrog is dependent upon water for reproduction.  Males will find a pond or ephemeral wet area , most often without fish, and call from high in a tree.  At Southern 8ths Farm, there is such a vernal pool not too far from where the two Cope’s shown in the photographs were found.  When the females come, the males climb down and they mate.  The females later lay their eggs in “packets” of between 30-40 eggs and attach them to aquatic vegetation.  Hatching and tadpole development times are highly dependent upon water temperatures, but transitioning from hatching to tadpoles and, finally, metamorphosis is in an average of 45-60 days.

A Cope's Gray Treefrog rests on a low limb of a Loblolly Pine (Pine taeda.)

A Cope’s Gray Treefrog rests on a low limb of a Loblolly Pine (Pinus taeda.)

Cope’s Gray Treefrogs are physically identical to Eastern Gray Treefrogs (Hyla versacolor) and should never be identified by appearance alone.  For many years, they were thought to be the same species, perhaps simply being two subspecies of the same species.  The calls of the two frogs; however, are different and provide a definite way to identify the two species.  The calls are also different enough that females from the two species do not tend to mate with a male of the other species.  For my fellow naturalist, (that would be you, the readers), the trill of the Cope’s is faster than the trill of the Eastern and, once you hear them, you can confidently tell them apart.

Genetic research has now given us more proof of these two species being separate from one another.  Recently, it has been discovered that Cope’s Gray Treefrogs have diploid chromosomes (two sets of chromosomes in each cell nuclei), while Eastern Gray Treefrogs have tetraploid chromosomes (four sets of chromosomes in each cell nuclei).  As we continue to make more advancements in all fields of science, such as biology, chemistry and genetics, we learn more and more about natural history.  This is the point in our discussion when I get excited and remind you how cool science is!

Another look at the beauty of a Cope’s Gray Treefrog at Southern 8ths Farm.  Note the granular skin and metallic looking grains.

Finally, I must tell you that this species is capable of secreting a slightly toxic substance from its skin.  While this will not harm you directly if you handle a Cope’s Gray Treefrog, you must be sure to wash your hands well after you are done.  This toxic skin secretion is known to irritate human eyes, mouths, mucus lining of noses and any open wounds.  To avoid the chance for discomfort, be very careful and mindful while handling the frog and please wash your hands well immediately when done.

Though colorations may vary between individuals, this overhead shot of a Cope's Gray Treefrog shows how beautiful it is.

Though colorations may vary between individuals, this overhead shot of a Cope’s Gray Treefrog shows how beautiful it is.

This Cope's Gray Treefrog blends in so well, it could almost appear as nothing more than a bump on this pine branch.

This Cope’s Gray Treefrog blends in so well, to the casual observer, it could almost appear as nothing more than a bump on this pine branch.  As naturalists, we slow down and look at the natural world.

As always, I encourage you to get outside.  Explore and marvel!  If you see our friend, the Cope’s Gray Treefrog, stop and admire it a while… knowing now it is far more than just background noise and is far more beautiful than some may think.

– Josh