AMPHIBIANS OF THE METRO AREA
METROPOLITAN  NATURALIST
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Grey Tree Frog (Hyla versicolor and Hyla chrysoscelis)

This common woodland frog is rarely seen but often heard. I often hear Grey Tree Frogs calling on rainy nights in the spring
and summer, and occasionally even in the fall. As the name suggests, these frogs spend much of their time in trees where they
eat small insects. On rainy nights they can be found around small ponds and puddles, where they find mates and lay eggs.

There are actually two separate, almost identical species of Grey Tree Frog, the Cope's Grey Tree Frog (
Hyla versicolor) and
the Eastern Grey Tree Frog (
Hyla chrysoscelis). Although the two species are indistinguishable to human eyes, hybrids are
believed to be very rare. The two species have different numbers of chromosomes and can be identified by laboratory methods
such as karyotyping or flow cytometry. The calls of the two species differ in the rate or speed of the call, but this is difficult to
discern unless the two species are calling side by side.
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The markings on the frog's back blend well with the bark of trees, making the frog very difficult to see when on a tree trunk
like the frog above. Grey Tree Frogs can change color, varying from grey to green to blend with their background, Sticky
pads on the frog's toes allow it to walk up the sides of trees and walls
We found this frog on a windowsill on our front porch. The frog may have been attracted by the bugs at the porch light.
When daylight came, he apparently thought this would be a good place to sleep through the day.
The male grey tree frog has a black throat, as seen in the picture above. In the picture below the frog is partially extending his
throat pouch. The male frog extends the pouch when he calls.
Grey Tree Frogs have yellow pigment on the underside of their hind legs. I am not sure what the function of this bright
color is, but I expect it might help the frog escape predators. When the frog jumps, a predator might see a flash of yellow
which disappears when the frog lands with its legs folded.

This strategy is similar to the white tailed deer, who waves the white underside of his tail when he runs. A predators eyes
are drawn to the white tail, and the deer seems to vanish when he drops his tail, hiding the white underside.