The raucous chorus
of Freddo Frog


He who planted the ear, shall He not hear? He who formed the eye, shall He not see?
Psalm 94:9

FEW SOUNDS PRODUCE SUCH EXTREME RESPONSES as the cacophonous din of a pond full of Freddos (that's frogs for those uninitiated in Aussie slang) in mating season. You love it or you hate it. I love it. The unforgettable din thrown up by a dozen or so frogs basking in wetness in a puddle by our back door in Brisbane years ago is one of the fondest memories I have of life in that lovely city.

But how well I remember the exasperated reaction of a student one springtime at a college I was studying at in England. One end of the men's residence was situated alongside the college lake. Each spring the predicted clamor of frenzied frogs drove this student mad. One night, after a number of sleepless nights, he snapped. Flinging open his bedroom window he threw the nearest object he could find at the poor amphibians. The nearest object was his own slipper. Being strapped for cash like all typical students, he could ill afford a new pair of slippers.

Why the racket?

Why do frogs ribbet so heartily? The simplest answer is; to attract a flirtatious female. Only male frogs take part in these mass vocal acrobatics. (Females do occasionally croak under certain circumstances.) Each participant is striving to outdo other males in the mating game. When circumstances are right, masses of male Romeos ply their trade in a bid to attract one of the many Juliets who respond to the crescendo. Many people are aware of the remarkable capacity of calling frogs to project their voices for a fairly great distance. This feat is accomplished by ballooning the vocal sacs.

It is commonly accepted that the quality of a male frog's outcry provides interested Fredwinas with information about Freddo's age, size and health. By responding to this information, a female may mate with the fittest male — God's way of ensuring maximum health of a population. (Not dumb evolution's way of improving the pedigree.)

Sometimes, however, it doesn't work out that way. Other males may not be able to outbrute a bigger male, but they may be able to outwit it. Such satellite males may sit quietly next to calling males, and when a female approaches the strumming Romeo, the interlopers leap before the strummer looks, and "hijack" the female. Once again, the health of the population is maintained, as brains are just as important as brawn in the matter of group survival.

To our untrained ears, it may appear a miracle that a female frog could filter out all the various frog calls and home in on a male of her own species. This is especially remarkable when you realize that up to a dozen different species can be calling from the same general location at the same time. Well, of course, it is a miracle. One requiring the infinitely superior mind of God to work out.

One design feature that God has built into frogs' brains to enable them to find a member of the right species to mate with is "tuning". The ears of females of each species are tuned to a particular call type, and they will not respond to calls of a different species. It may seem obvious to us that each species would produce a call characteristic of that species, but this was not generally understood by the specialists in the field until the late 1950s. At that time it was realized that each kind of frog has a call that is as unique to it as the calls of birds are to them. One of the reasons why frogologists were skeptical about such an idea was their belief that the ears of frogs were not sufficiently refined to permit them to differentiate to such an acute degree. Now scientists know that “different amphibian ‘users' of the acoustic space… occupy private channels” (Narins, Peter M. August 1995, Frog Communication, Scientific American p. 62).

Another design feature is called "spatial isolation". The males of a given species are not distributed haphazardly at a given site, but are found in congregations. For instance, males of some species call while floating in the water, while others call from clumps of grass, or sitting in the shallows at the water's edge, from shallow burrows in the ground, or from vegetation overhanging the pond, and so forth. Once again, the ingenuity of God is clearly demonstrated.

Ear to the ground

Of course, there are surprises awaiting researchers at every bend of the road. Just when you think they have milked every possible drop of information there is on a given subject, something unexpected pops up. Scientists recently discovered that one species of frog — the white-lipped frog of Puerto Rico — appears to communicate by another means as well. And perhaps for a different purpose than mating. The means is by producing vibrations in the ground. The purpose is probably to tell other males just where he is and thus warn them to stay away.

It has long been known that most frogs are extremely sensitive to the minutest vibrations in the ground. A gentle footfall can quiet a calling male many meters away. This sensitivity lies in a structure of the ear known as the saccule. The saccule contains a large stony mass, and it is believed that as soil vibrations are transmitted through a frog's body, the stony mass moves less than the surrounding tissues, setting up strains that stimulate nerve endings in the saccule. It has been known that this sensitivity enables frogs to sense approaching predators.

The white-lipped frog was discovered to generate, and respond to, vibrations of its own — a behavior never before reported in vertebrates. By using sensitive apparatus, the investigators found that when a male frog calls, it generates a seismic signal in the soil. As males call, they crouch low, pressing their vocal sac to the soil. The vibrations may be generated when the sac, expanding with each chirp, thumps the ground. What'll God think of next?

What's the point? Well, like proper scientists, the discoverers of this phenomenon don't want to be overly dogmatic, but they believe that the signals enable the frogs to claim and proclaim their territory against other males. The vibrations propagate through the soil at about one third the speed of the accompanying sound as it courses through the air. The delay between the respective sound and vibration as it arrives at a nearby frog enables it to calculate the distance of the transmitting male. This way, this species of frog is able to space itself out according to its territorial needs for food. As with all animals, if the frogs were too close to each other, there would not be enough food to go around, and all would perish. This is one more intriguing way God has created to enable a species of animal to ensure proper spacing of its kind.

A whole lot more could be said about this fascinating topic. This gives but the tiniest introduction to a vast subject. But it should be enough to emphasize yet again that God knows what He's doing.

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