A Natural View: Frogs, Toads, and Other Things

Terry Sprague

Male Spring Peeper (Pseudacris crucifer) with vocal sac inflated as it sings
[This article ran in the February/March 2011 issue of The SCOOP.]

Those who watched the classic film Deliverance from the early 1970s will not soon forget the disturbing scenes of four canoeists paddling down the wild Cahulawassee River in Georgia. The movie, however, did have a powerful environmental message that was way ahead of its time. As a naturalist though, I was really paying more attention to the sounds in the background — the piercing bleats of Fowler's toads.

We can safely assume that the repeated screams of the Fowler's toad were not dubbed in for effect, but rather, had been calling naturally when the scenes were recorded. Certainly, they are common in Georgia and range all the way north to Lake Erie, where a small population of fewer than a thousand can be found along the lake's north shore. We won't hear them in eastern Ontario, but we do have nine or ten other species of frogs and toads to delight us as spring once again makes its debut.

Every March for the past ten years I have conducted a workshop on behalf of the Community Wildlife Monitoring Program (CWMP) in which I am involved. The workshops ease volunteers into the art of identifying those mysterious sounds that emanate every spring from the depths of the wetlands. The purpose of the program I operate is to monitor the successes and failures of amphibians as a way of determining the health of the wetlands in our area. Frogs and toads are very sensitive to environmental changes and have become important indicators in the CWMP in the Bay of Quinte area. The long-term goal is to remove the Bay of Quinte from an Area of Concern to An Area In Recovery.

The public is drawn to frogs and the program is an easy one to get people excited about. Over 100 people attended last year's workshop, eager to learn the species of frogs and differentiate between the calls. For families, there was Ontario FrogWatch, and for those wanting the challenge of a more structured survey, the popular Marsh Monitoring Program, operated through Bird Studies Canada.

The frog chorus began very early last spring — some claimed hearing chorus frogs as early as March 17th. Generally, it is the raspy notes of wood frogs that herald the spring chorus, sounding like a small misplaced gathering of tiny ducks quacking from wooded areas. They are the first to call because Nature has gifted them with an ability to scoff at those who hibernate and instead, allow themselves to freeze solid over winter. They are members of a rather exclusive club of vertebrate animals that overwinter on dry land and survive the freezing of their body tissues. World-wide there are only a few species of vertebrates that can tolerate freezing like this. They may freeze and thaw several times in March before spring has truly arrived.

The sounds we hear coming from roadside ditches and vernal pools that form in early spring belong to chorus frogs, resembling the sound of fingernails being dragged lengthwise down the teeth of a comb. For them, life is a hustle as roadside ditches and temporary ponds will soon dry up. Their eggs hatch in as few as three days, but it takes a month for the tadpoles to develop into froglets with lungs that will enable them to survive without benefit of gills.

Next, it's the spring peepers' turn to dominate the evening air with their sharp notes. As the water warms, thousands will break into a din, like the sound of distant sleigh bells. They may not measure more than an inch in size, but can produce more decibels of sound per pound than any other living creature. Some researchers claim that one spring peeper call has the same decibel rating of an airport runway.

There is such a variety of instrumentation out there in the frog chorale that it actually becomes quite easy to identify them by voice alone. We all know the rattling snore of the leopard frog, and they are no stranger to any of us, appearing everywhere, even on our lawns at certain times of the year. They are so plentiful they actually become a hazard on highways, as hundreds of them hopping from one side of the road to the other become victims of traffic, creating a slimy and dangerous surface upon which to drive.

Later in the spring we will hear another frog, the “bong” note of the green frog. It closely resembles someone plucking a banjo string, and we can hear them calling from nearly every cattail marsh, mixed in with the other invisible sounds that are produced nightly from the sedges and cattails.

We need to be patient before we hear the bass chorus of the bullfrog, as they prefer much warmer temperatures before they are prompted to sing. My parents first identified these creatures for me when I was only a few years old. Since the only bull I could relate to was the Holstein bull tethered out in the pasture field, I had fabricated terrifying images in my mind of something extremely large and formidable crouched low in the cattails, ready to attack if I dared get too close. They are our largest frog, reaching an incredible six inches in size. Although there have been some concerns about the overall population of bullfrogs, I find them somewhat cyclic, some years in low numbers, other times producing a thunderous roar every evening, the chorus starting low and then exploding into a deafening crescendo that resembles an approaching thunderstorm.

There is another frog that comes still later — the grey tree frog. First timers hearing this sound are almost certain they have stumbled upon a mysterious bird of some sort, or perhaps a raccoon, as the sounds are similar. Often, they appear to originate from trees, and likely they do, as this species' feet have been thoughtfully provided with tiny suction cups which enable them to stick to just about anything. It is not possible to appreciate its extremely loud rattling trill, until a tree frog has crawled up the side of the house and has decided to call all night right beside an open window. It was several days before I actually was able to locate the frog, but ended up leaving it there, so intrigued was I by its call.

The long, wavering trill of the American toad will be on the scene too before we know it. This is one of the more pleasant sounds we hear each spring, and they often get so turned on during the mating season it is possible to approach calling individuals within a few inches. One of my best photos was taken with a macro lens at a conservation area pond near Picton. The toad made no effort to hide as I snapped its picture at close range with a half dozen or so kids not far from it engaged in a noisy pond study.

One of my favourites has always been the mink frog and it is a sound synonymous with northern bogs and wetlands. Their range tends to be north of Highway 7 and I have heard choruses of them tapping away like a hammer against wood at Machesney Lake near Bon Echo, and near Madoc. In recent years there have been many reliable reports south of Highway 7 indicating an expansion of their breeding range. Pickerel frogs with their distinctive low snore prefer cooler streams and can sometimes be found with mink frogs but seem to be less common south of Highway 7.

While we won't hear the bleating calls of the Fowler's toad in our part of Ontario, its absence is certainly more than made up by a spectacular variety of calls that will accent the wetland scene as we advance cautiously into yet another spring.

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Cutline for attached photos:
1) The green frog is easily identified by its banjo like call. Photo by Paul Johanson

2) This American toad showed no concern at all while being photographed at close range. Photo by Terry Sprague