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Vernal Cacophony

By Ranger Steve Mueller


Sit by a vernal pond that will dry by late summer to experience joyous ear pain during April. Listen to the massive cacophony of thousands of frogs vying for the chance to mate. Each species has a unique mating call.

Spring peepers make enough noise in the spring to cause ear pain.

Spring peepers have a single peep but when in mass with other peepers, the sound will generate enough volume to cause ear pain. When you are somewhat distant from a pond, the noise is a pleasant sign of spring. Western chorus frogs make a sound compared with running your thumb across the teeth of a comb. For some reason chorus frogs and their calls have become less abundant. Wood frogs are the third early spring species. They generate a duck-like quack. It seems wood frogs have the shortest period for making mating calls. 

The three early callers actively seek mates as soon as ice melt begins on ponds. They often do not wait for ice to clear the entire pond. If a warm rain arrives, the activity and volume maximize. 

The greatest activity is at night, but daytime choruses abound. Walk to a pond and, as you approach, all will become quiet. Sit quietly and remain still for a few minutes. Soon a brave peeper will venture its call. Another will follow with many soon joining. Continue to be quiet and move your hands slowly so you do not alarm the frogs. Cup your hands in front of your ears with palms facing back. Notice how greatly the sound is diminished when your hands block the sound. Rotate your cupped hands behind your ears. You will not be able to tolerate the volume for long. Cupped hands behind your ears catch the sound and direct too much volume to your ears. It will be necessary to remove your artificially enlarged ear pinnae because of physical pain.

Frogs instinctively grab a nearby frog and begin squeezing to force egg laying. As eggs come out, the males milt filled with sperm fertilizes an egg cluster. A jelly mass containing eggs soaks up water and will become larger than the frog that laid it. Anxious males often grab a nearby male by mistake. The grabbed male will protest with a unique trill that means let go. Listen and you should be able to recognize this sound. 

The egg masses are attached to twigs, vegetation, or debris in temporary spring ponds. Survival is extremely difficult for amphibian eggs. Best survival is in the temporary vernal ponds that dry by midsummer because fish are absent. This allows for eggs to develop without being eaten. Many insects will eat the eggs as well as some birds. Small vernal ponds are often filled or drained by people, but they are essential for frogs.

Counter shading helps hide the eggs. Find a cluster of eggs and lift it from the water. Notice the eggs are surrounded by jelly that protects the eggs. The top of each egg is dark. When a predator is peering into the pond, the dark blends with the bottom and helps camouflage the developing embryo. From beneath they are hidden from underwater predators by having a light or white coloration that blends with the sky above. Algae and cyanobacteria grow in the jelly making it green and they gradually digest it. By the time the polliwogs are ready to escape their protective gel, it is adequately decomposed to allow the young frogs to break loose and swim freely into the water. 

As water warms, larger frogs begin calling and mating activity. Gray tree frogs have a short loud trill that stops abruptly. They continue their calling well into summer even after they leave ponds. Leopard and pickerel frogs have a ratchet-like call that is compared with snoring. When the air temperature reaches 70ºF, American toads and bull frogs begin their calling. The American toad has a trill somewhat like the gray tree frog, but it continues for an excessively long time. 

Make a trilling sound yourself by vibrating your tongue behind your teeth and try to continue until you are out of breath. That will be about how long the toad sings. Frogs pass air back and forth between their lungs and mouth when calling and do not expel air like we do when making sounds. Each frog species call is unique for its mating nature niche. Most depend on temporary ponds. Green frog and bull frog tadpoles require more than one year to develop so they require permanent ponds. Spend time enjoying the vernal cacophony.

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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