By Rick Borchelt
During our first few spring-like days back in March, when daytime temperatures were in the 50s and nighttime lows nudged above 40 for the first time since Christmas, I got off the train at the College Park Metro station just as it was getting dark. I paused on the north end of the platform to listen, and in just a few minutes, from the little pond just to the left of the platform, I heard a few tentative peeps. They were quickly joined by a few more, until they became a pulsating wall of sound coming from the little pond.
These piercing sounds were broadcast by the aptly named spring peeper (Pseudacris crucifer), a frog the size of a dime that seasonally gathers around small pools, watery ditches, and the margins of lakes and ponds for a flurry of mating and egg laying. The male frogs make all the noise as they jockey to lure a female into the water to mate. Tadpoles hatch out a few weeks later, and by late summer, they’ve transformed into frogs who will be joining the chorus next spring.
Photo credit: Rick Borchelt
And what of the hundreds of spring peepers who gathered that evening near the Metro station? By late April, the adults had dispersed into the surrounding woodlands to live a largely arboreal life, feasting on small insects, snails and other invertebrates. Without their seasonal urge to mate, the males are mostly silent, though you may hear a shrill peep or two from the woods around town in the late fall or during warm spells in the winter.
Spring peepers aren’t the only amphibian songsters in College Park, though. We often hear another set of calls this time of year, especially on afternoons when the humidity is high or the sky suggests rain. These are the calls of true treefrogs, and we are lucky enough to have three different kinds of them in our neighborhood. These frogs, all about the size of quarter, spend their days tucked away on railings, on hose reels or on flowerpots; at night they come out onto decks and porches, where they dine on insects attracted by our artificial lights.
The easiest way to identify a green treefrog (Hyla cinerea) is by color; true to their name, they are almost always some shade of green. And these frogs come by their color with a bit of magic; their smooth skin is naturally blue, and the frog produces a yellow pigment, on demand, that overlays this blue canvas to create a green appearance. A frog adds just enough yellow to blend in with the dominant green of the plants it sits in at any given moment. Occasionally a green treefrog doesn’t live up to its name, though; a frog that can’t produce yellow pigment remains a vivid blue its entire life — which may turn out to be unfortunately short. These genetic anomalies, with their bright blue skin, stand out like a sore thumb and are easily spotted by natural predators such as snakes, small mammals and large birds.
In addition to green treefrogs, we have two kinds of gray treefrogs in College Park: the unimaginatively named gray treefrog (Hyla versicolor) and the Cope’s gray treefrog (Hyla chrysoscelis). These frogs both have gray or gray-green bumpy skin that’s patterned like bark or lichens, and they look virtually identical to each other; only by their calls can you tell them apart. The call of the gray treefrog is a short, flute-like trill, while the Cope’s call is faster and higher pitched. (Green treefrogs, by contrast, make a sound more like a sharp honk or bark.)
All three treefrog species here are sometimes called rain frogs because they often sing just before or after a storm. They call for mates, off and on through the summer, always close to small pools of water where they can breed. When it rains, these puddles and birdbaths – and even knots in trees — are suddenly full, and the waiting frogs sound off to alert females that a choice breeding site and sperm donor await them.
Pennsylvania Herp Identification, a.k.a. PAHerps (paherps.com/herps/frogs-toads/), offers a database of common frogs and toads found in the Mid-Atlantic, including the treefrogs that hop about the city. The database is an excellent resource and includes a comprehensive photo library as well as clips that allow you to listen to calls. I encourage you to explore the site; you may even recognize a leaper from our woods here in College Park.
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Have questions for Rick about the world of nature in and around the city, or suggestions for future College Park Wild columns? Drop him a note at rborchelt@gmail.com.
