Cynthia Coleman, age 13, of Kentfield, California, for her question:
Do porpoises really make noises?
The porpoise and dolphin have been studied in marine aquariums on both our east and west coasts. All the experts report that these small members of the whale clan passed their I.Q. tests with flying colors. Several research teams also reported that they are just about the gabbiest creatures in the salty seas. However, so far nobody is quite certain how they make their noisy chirps, whistles and giggles.
The porpoises and dolphins are cetaceans who share certain remarkable family features with the huge ocean going whales. They are, of course, air breathing, warm blooded mammals who give birth to live babies. They are very sociable animals, fond of each other's company and extremely good parents. But the most outstanding quality of the cetaceans is intelligence. They make good use of their extra large brains and some researchers suspect that they may be the smartest animals in the whole world.
Most other cetaceans travel in family groups enjoying their merry marine life to the full. Naturally they keep in constant contact with each other, both for reasons of safety and sociability. Apparently they have a sort of built in radar system, similar to the bat's. This system echos ultrasonic sounds, way above the human hearing range, which is about 20,000 cycles per second. To make it work, the porpoise must have super keen hearing, plus a method for creating sounds.
Tests prove that the inner ears of the average porpoise can detect sounds up to 100,000 cycles per second. Hydrophones are sensitive instruments for detecting ultrasonics and normal sounds under water. When let down near a school of playful porpoises, these instruments record a constant racket of barks and bleats, clicks and creaks, quacks and squawks, plus an assortment of whistles and other noises in the ultrasonic range.
Sounds of all sorts travel much faster and more easily through the water than air. And the porpoise has just the right ears to hear them. The tubes that lead to his inner ears are plugged with thick wax, which acts as a good sound conductor. We are not so certain how he utters his noisy conversation. However, a few researchers believe that the porpoise can imitate the human voice. Some years back, it was reported that a certain porpoise took it upon himself to repeat a man's speech. When the man told his wife about it, she laughed loud and clear. The copycat porpoise imitated that, too or so the story goes.
There is reliable evidence that porpoises have a sizeable vocabularly for communicating among themselves. Also, they obviously use their radar systems to locate food and obstacles. Normal sounds, such as high C, can echo from an ocean going liner. But porpoises need super keen hearing to detect the ultrasonic echos from smaller objects such as interesting food items.