A frog’s tympanic membrane, or tympanum, is the circular patch of skin directly behind its eye that we commonly call its eardrum. It functions much like our eardrum does –the tympanum transmits sound waves to the middle and inner ear, allowing a frog to hear both in the air and below water. In addition, this membrane serves to keep water and debris from entering a frog’s ears. In some species of frogs, such as the Green Frog, American Bullfrog and Mink Frog, their gender can be determined by the size of their tympanum relative to their eye: the male’s tympanum is larger than its eye, the female’s is equal in size or smaller than its eye.
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If you’ve spent time at a pond recently and heard what sounded like someone snoring, you weren’t hallucinating! Male pickerel frogs have started calling to attract mates, and each species of frog, just like birds, has its own distinctive call. Spring peepers peep, wood frogs clack and pickerel frogs snore. Their snore isn’t long – it only lasts a second or two — but it’s unmistakable. Pickerel frogs call from under water, as well as on top of mounds of vegetation, so if you hear one and then search for it, it’s very possible you may not find it. (My sincere apologies-computer failure prevented me from posting on the previous two days.)
“Peeps” and “quacks” fill the air these days. How is it that these frog calls travel so far? It’s all thanks to a thin membrane , or sac, that most frogs have. Note the single inflated sac of the spring peeper, and the paired sacs on either side of the wood frog’s head. These vocal sacs act as resonating chambers, causing the male frog’s mating call to be amplified and carried far (some species of frogs can be heard over half a mile away). Most frogs have one of three basic types of vocal sacs: a single throat sac (the most common), paired throat sacs (partially separated by connective tissue) and paired lateral sacs (completely separate chambers on either side of the head). Vocal sacs are outpocketings of the floor of the frog’s mouth. When calling, a frog closes its mouth and nostrils, and expels air from its lungs through the larynx and into the vocal sacs. The vibrations of the larynx emit a sound which resonates within the vocal sacs. The frog continues calling as muscles within its body wall force the air back and forth between the lungs and vocal sac. The thickness of the vocal sac wall in frogs varies. Typically, small frogs that call in the air (spring peeper) have thin vocal sac walls, whereas those that call in the water, particularly large species (green and bull frogs) often have thick-walled vocal sacs that appear swollen, not inflated like a balloon, when filled with air.
Common Mergansers are primarily fish-eating ducks. Young mergansers require over half a pound of food per day during their first summer, and often supplement their fish diet with insects, mollusks, crustaceans, worms, frogs, small mammals, birds and plants. The pictured immature Common Merganser had just downed a crayfish when it spotted a frog which it succeeded in catching and eventually swallowing.
Although Spring Peepers emerged from hibernation about two months ago, on warm nights the males are still advertising for mates and will continue to do so into June. Let your ears guide you to the peepers as they call repeatedly, often while perched on low vegetation near water. Armed with a flashlight, look for the movement of their vocal sacs as they inflate and deflate as the peepers sing.
After noticing the sudden loud clacking chorus at a nearby temporary woodland vernal pool, I went down to investigate, and there were dozens of wood frogs floating on the surface, as they croaked their duck-like quacks in the hopes of attracting female wood frogs. As far as I could determine, they were out of luck on this, their first day at the breeding pool, as I don’t believe the females have arrived yet. One clue was the relatively small size of the floating frogs and it seemed as though every frog was calling (only males call). Plus, time after time a wood frog would swim up to another wood frog and attempt to grasp it only to have the object of its desire utter a “release” chirp (a call made only when a male clasps another male) and swim rapidly away.
I heard my first peeper on March 18th, roughly two weeks earlier than in past years. These tiny members of the treefrog family begin mating rituals shortly after the end of hibernation. The males gather at small pools by the hundreds. Each male establishes a small territory and begins calling the familiar high-pitched “peep” quite frequently. The louder and faster he peeps, the better his chances are of attracting a receptive female. Males usually compete in trios, and the male with the lowest-pitched call usually starts the vocal competition. If you look closely at the peeper in the photograph you can see some snow fleas hitching a ride.
You may well have heard the single “peep” of a male spring peeper emanating from the woods recently. It does seem odd to hear this call now, often far from water, as we associate it with spring courtship. This phenomenon occurs so regularly in the fall that herpetologists have given it a name – “fall echo.” They speculate that peeper calling is spurred by light and temperature conditions, when fall climate conditions are similar to those of spring.
Next to the green frog, the pickerel frog is the most abundant frog in New England. It is often confused with the northern leopard frog, which it closely resembles. The spots on a pickerel frog’s back are squarish and aligned in rows, whereas the leopard frog’s spots are rounded, and randomly scattered over its back. In addition, the male pickerel frog has bright orange on the inner surface of its hind legs, which the leopard frog lacks. The pickerel frog is very sensitive to pollution, so its presence is indicative of good water quality.