Pig-Boats & Whales

Every veteran of submarine war patrols has stories of false "enemy contacts" reported by underwater detecting devices. If the signals were only reflections of the high-frequency sound waves sent out by the sub itself, false alarms could easily be caused by whales or schools of fish. But far more baffling were the cases in which a different sound impulse was recorded. This, it seemed, might be the enemy's own detection device at work. Many a crew was called to battle stations ready for deep-sea combat, only to learn that the signals had been lost. It was most confusing.

Last week the Woods Hole Oceanographic Institution announced that for two years one of its ichthyologists had been working on an explanation. Mrs. Marie Poland Fish dredged the Navy's submarine logs, made seasonal charts of the points where false enemy signals had been reported. Then she made charts showing where whales and other big marine mammals were at the same seasons. Each pair of charts matched.

One possible conclusion: whales and their kin were the real inventors of sonar.* What they used it for, men can only guess. Mrs. Fish found apparent confirmation of the theory in the pig-boats' logs: when a sub jammed the "enemy's signal by sending out its own sound waves, the transmission stopped. Evidently the whales were confused, too.

*A method of undersea detection, highly developed in World War II, employing easily focused high-frequency sound waves near the upper edge of the audible range. A large object in the water sends back an echo; its distance from the submarine is computed by timing the echo.

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