Thursday, June 11, 2009

Summer Frog Chorus

It has been a while since we've mentioned anything about the amphibious wildlife here at the sanctuary. Late March and early April brought about a flurry of amphibian activity that's unrivaled at any other time of the year, but not all species were involved. As the spring days lengthen and warm, slowly giving way to summer, our area's other frogs become more active and vocal.

Warm days and humid evenings over the last few weeks have encouraged the Bullfrogs (Rana catesbeiana) and Green Frogs (Rana clamitans) to begin their breeding seasons. Nearly any pond, lake, and wetland will be full of the deep "jug-o-rum" voice of the Bullfrog and the "loose banjo string" voice of the Green Frog. Another species involved in the chorus is no less noticeable, but is far more difficult to locate.

Gray Treefrogs (Hyla versicolor) are stepping up their breeding efforts at this time of year as well. They are most vocal from late spring through early summer during the evening and night hours, but are also likely to call during warm overcast afternoons. As the name Treefrog implies, they typically inhabit forests, but are also common in neighborhoods and gardens with plenty of vegetation for hiding and foraging. Their loud, trilling voice announces their presence, but their extraordinary camouflage makes them difficult to see.

I've been hearing a couple of Gray Treefrogs calling around the museum and naturalist's cottage for the past week. One in particular always sounds very close to the cottage, but I was unable to find him for a few days. In the evening as the sun is setting and after dark with a flashlight, my search came up empty. This past weekend I finally found him near the wildlife garden beside the cottage.
Can you find the frog in the photo?

My first pass through the garden came up empty, but I knew he was in there. There's a lot of flowers and other plants in which he may have been hiding. There are a lot of spaces between the rocks around the garden's pond as well. I knew I was close because he stopped calling during my search.

After I walked away for a few minutes, he started calling again. As I approached the garden, he stopped. I knew that he had to be close to the front of the garden. I retreated again and went to grab my binoculars. The incredible camouflage of this frog's skin would make him hard to spot, but the frog's calling creates movement. Scanning carefully across the front of the garden with my binos, here is what I found:
Can you see him now?

Each time he called, his throat would swell to resonate the sound into the surrounding area. This little bit of movement was enough to locate the frog in his secret location. What a perfect place to hide. Look at the photo below to see how well this guy is capable of melting into the background of his hiding place:
Gray Treefrog (Hyla versicolor)
As their scientific name implies, this frog is capable of changing colors to match it's surroundings. Colors can vary from nearly black to nearly white with varying degrees of mottling. If you're lucky enough to find and handle a Gray Treefrog, you'll notice bright yellow patches on the underside of it's hind legs. Quite an extraordinary sight from such a well camouflaged animal.

Enjoy this summer's frog chorus and keep an eye out for the froglets of various species emerging from our local ponds and wetlands.

-Adam Zorn, Naturalist

No comments: