Chorus frog calls herald arrival of spring
If seeing is believing, then I am, at long last, a believer.
Every April I have followed the sound of chorus frogs to find the source.
I have sat motionless on logs, stood still as a statue in ankle-deep water, and peered silently into murky water.
Looking, waiting, searching amidst the ear-piercing cacophony of frog calls. Never a frog in sight.
This futile search became an April ritual for me. I was beginning to think that chorus frogs were a hoax and the din in my ears, just a bad case of tinnitus.
This Doubting Thomas became a true believer last week, when I saw not just one chorus frog, but two!
Two tiny frogs out of thousands calling all around me. I couldn't jump for joy at my discovery, partly because I would have fallen off the log I crouched on, and every frog in the pond would disappear. But my heart sang silent hallelujahs.
Chorus frogs in Kane County (Western chorus frogs, to be exact) are tiny, well-camouflaged amphibians. They're only 1 to 1½ inches long, the color of mud, with subtle stripes along their backs - perfectly hidden in wet vegetation. By comparison, the easy-to-spot leopard frog is huge, the rotund American toad enormous, and the bullfrog gigantic.
Western chorus frogs show a preference for temporary bodies of water. Predators therefore can't count on them as a food source. In dry years, though, Western chorus frogs may be out of luck.
Without "fluddles" (puddles in flooded fields), breeding grounds are limited. This year, they're in good shape.
The challenge presented by breeding in temporary waters is to get the job done quickly. Fields can dry up in no time.
There is a sense of urgency in the outbursts of chorus frog calls in March and April. "Pick me! Here I am! Look here! I'm your man!"
The tiny males find a perch - any stick or blade of grass can serve as a stage - and the performance begins. Each tries to outdo the others, and what seems like noise to human ears, is a beautiful serenade to female frog ears.
It was pretty fun to watch the two male frogs on their little platforms. In fact, the glint of their rapidly moving vocal sacs is what caught my eye.
The sacs are yellow and add a little bling to the otherwise dull-looking males.
Research indicates that the pulsating movement of the vocal sac may serve as a visual cue to females, adding to the allure of the singing male.
The sac is an elastic membrane that expands with a rush of air from the lungs. (Kind of like blowing a bubble with bubble gum.)
Expansion and contraction of the vocal sac takes a split second.
The warmer the temperature, the higher the frequency of calls.
If chorus frogs had a speech teacher who told them, "Project!" - they certainly took it to heart.
These tiny guys can really belt it out. Their stentorian calls travel as far as a quarter mile, from pond to puddle to prairie.
Western chorus frog calls dominate the soundscape on a warm day, out-singing the redwing blackbirds and the song sparrows.
Western chorus frogs and their amphibian compatriots are pretty important in this day and age of environmental change. Their presence, and their absence, tells of the quality of habitat.
Frogs are highly susceptible to pollution due to their semi-permeable skin, and populations plummet when habitat declines.
If we don't hear a certain species at all, and if we can't find any individuals, we know that something has gone awry with their habitat.
Conversely, if we hear lots of frog choruses, croaks, and calls, we know that they have found decent habitat.
Wildlife biologists and citizen scientists (trained volunteers) monitor frog populations each year to note trends.
Listen for Western chorus frogs this week as they wind up their breeding season.
Soon they will be quiet, as mating is complete and tadpoles swim in the ponds.
If you can steal away and sit quietly at the edge of a wetland, you just may get lucky, as I did, and see a tiny chorister in the throes of a love song.
• Valerie Blaine is the nature programs manager for the Forest Preserve District of Kane County. You may reach her by emailing blainevalerie@kaneforest.com.
Who's calling?How to tell apart frog calls
Each species of frog has a characteristic call - and none of them say "Ribbit!"
Learning frog calls is a matter of practice, and learning catchy comparisons to help you remember.
The Western chorus frog, for example, sounds like someone running a finger across the teeth of a comb.
The green frog sounds like the plucking of a banjo string.
The Northern leopard frog sounds like an old man snoring.
Check out this website to hear the songs of some of our native frogs: <a href="https://www.umesc.usgs.gov/terrestrial/amphibians/armi/frog_calls.html">www.umesc.usgs.gov/terrestrial/amphibians/armi/frog_calls.html</a>
-Valerie Blaine