Emperor penguins do a number of amazing things — waddle 70 miles over ice at 80 below in 100-mph winds, go without food during their 63-day gestation period, etc. — but one of their amazing feats involves information theory, not fortitude. For Family Survival, Penguins Play a Game Of ‘Name That Tune’:
Penguins may look pretty much alike even to other penguins, but they don’t sound alike. To generate their unique calls, scientists have discovered, the birds use two voice boxes. That lets them emit different calls simultaneously, modulating frequency, amplitude and beat, write Thierry Aubin of the Universit?Paris-Sud, Orsay, and Pierre Jouventin of the Center for Functional Ecology and Evolution, Montpellier, France.The interaction of two frequencies generates beats that penetrate solid objects such as, oh, huddled penguin bodies as dense as 10 birds per square meter. In addition, the system creates a huge variety of ‘vocal signatures.’
Adults emit highly individual calls of four to eight syllables. A chick, which memorizes dad’s call during the five weeks it spends sitting atop his feet, plays a life-or-death game of ‘name that tune,’ identifying him as he waddles through the colony like a bowling pin with feet and calls at regular intervals.
Playing recorded calls for king penguin chicks, Prof. Aubin and Prof. Jouventin find that even a syllable or two is enough for most hatchlings to recognize mom or dad (though they usually wait for at least four before leaving the cr?che, apparently wanting to be sure).
From acoustics alone, the chicks should not be able to distinguish their parents’ call from more than about 25 feet, beyond which the signal-to-noise ratio drops below 1. Yet, just like humans in the din of a cocktail party, they can pick out their partner’s voice across the room (especially if the voice says something like, ‘Wow, you look terrific; have you been working out?’). Penguins can recognize a mate’s or parent’s call despite background noise and acoustic jamming by other calls.