The Sea Inside

the same device found on porpoises and dolphins. Known as the
museau de singe
or phonic lips, they operate rather like a human voice-box, sending the rapid sounds back through the whale’s internal, right nasal passage and through its ‘upper case’, a reservoir of oil with bio-acoustical properties.
    Having travelled all the way to the back of the whale’s concave cranium, the sound then bounces from an air sac, then returns through the ‘lower case’, filled with convex compartments of spermaceti oil which act as acoustic lenses. Only then, having passed from the front to the back of the whale’s head and back to the front again, is this powerful, refined sound emitted from its nose and out into the ocean. Then the whole procedure begins again (and all this at rates of a hundred times a minute). The highly directional sonar pulse bounces back from its target to be received, not through the whale’s outer ear, which would barely admit my little finger, but through its huge tuning-fork jaw. From there it is conducted to its inner ear. It has even been suggested that the rows of teeth along a sperm whale’s jaw act as regulators of this industrial-scale sound system.
    Reduced rather than amplified through João’s puny loudspeaker, the whales’ clicking scans the ocean a thousand metres below. It is the sound of control, at its peak, the loudest noise made by any animal, louder than a jet engine; but it is also entirely subtle, obeying its own laws of sequence, timbre and rhythm.
    First come the chattering ‘codas’ as the whales appear to discuss what they are about to do, or tell a waiting calf, ‘I’ll be right back’ – not unlike the shearwaters. Then follows a regular pulse, scoping out the ocean bed, sizing up the field, as it were. Next come the regular clicks that indicate a diving whale is searching for prey. If it is successful, it will emit a series of accelerated buzzes that mean it has locked onto something to eat, and on which it may still be feeding as it returns to the surface to resume its social codas. These may mean nothing more than ‘I’m back,’ but they could have more complex, conversational associations. These are, after all, animals with the biggest brains in nature, with a matrilineal culture reaching back for millennia. They are as different from other whales as ravens are from other birds;
über
-whales, a species set apart.
    If we pay attention, says João, we can hear the rhythms of individual whales, as characteristic as a Cory’s cry. ‘Some are more metallic than others – it’s their different voices,’ he says, in his own clipped fashion. This is the cocktail-party effect on a gigantic scale, but it doesn’t always do to shout. ‘At the surface, they’re silent. They don’t want to be heard by predators. And since they can see here, they don’t need their sonar.’
    Together with Yuri, João’s first mate – a tall French boy with cropped dark hair – we discuss the naming of the whale. In French, as in other Latin languages, the sperm whale is known as the
cachalot
; Yuri points out that this has a double meaning: it sounds like
cacher à l’eau
– to hide in the water. To speak is to draw attention to yourself, and beyond the bounds of your tribe attention is seldom welcome. That’s why the whales are silent at the surface, where they come closest to us: in silence they might also be invisible, these hiders in the sea.
    Yet shouting is what whales do best. They live in an element in which noise travels five times faster than in air. Their brains are wired for sound; their auditory cortex is larger than our visual cortex. Such a capacity is essential for animals that hunt in the lightless depths. Theirs is a very different experience of the world from ours, because their world is so different. For toothed whales blessed with pin-sharp sonar accuracy, everything is transparent; nothing is concealed. They live in another dimension, able to see into and through the solid, to discern structures inside. A whale or a dolphin can see the interior of my body as accurately as I can see the exterior of hers; I must resemble one of the educational models we had at school, clear plastic figurines of a man and a woman with their organs indecently displayed. The world is naked to a cetacean.
    In his book
In Defense of Dolphins
, Thomas I. White, a professor of ethics, notes that his subjects are able to use their sonar to detect one another’s emotional